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C8051F91x-C8051F90x
Single/Dual Battery, 0.9-3.6 V, 16-8 kB, SmaRTClock, 12/10-Bit ADC MCU Ultra-Low Power - 160 uA/MHz in active mode (24.5 MHz clock) - 2 us wake-up time (two-cell mode) - 10 nA sleep mode with memory retention; - 50 nA sleep mode with brownout detector - 300 nA sleep mode with LFO (`F912/02 only) - 600 nA sleep mode with external crystal Supply Voltage 0.9 to 3.6 V - One-cell mode supports 0.9 to 1.8 V operation
(`F911/01). `F912 and `F902 devices can operate from 0.9 to 3.6 V continuously - Two-cell mode supports 1.8 to 3.6 V operation - Built-in dc-dc converter with 1.8 to 3.3 V output for use in one-cell mode - Built-in LDO regulator allows a high analog supply voltage and low digital core voltage - 2 built in supply monitors (brownout detectors) 12-Bit or 10-Bit Analog to Digital Converter - 1 LSB INL (10-bit mode); 1.5 LSB INL (12-bit mode, `F912/02 only) no missing codes - Programmable throughput up to 300 ksps (10-Bit Mode) or 75 ksps (12-bit mode, `F912/02 only) - Up to 15 external inputs - On-chip voltage reference - On-Chip PGA allows measuring voltages up to twice the reference voltage - 16-bit auto-averaging accumulator with burst mode provides increased ADC resolution - Data dependent windowed interrupt generator - Built-in temperature sensor
High-Speed 8051 C Core - Pipelined instruction architecture; executes 70% of
instructions in 1 or 2 system clocks
- Up to 25 MIPS throughput with 25 MHz clock - Expanded interrupt handler Memory - 768 bytes RAM - 16 kB (`F912/1), or 8 kB (`F902/1) Flash; In-system
programmable
Digital Peripherals - 16 port I/O; All 5 V tolerant with high sink current and programmable drive strength Hardware SMBusTM (I2CTM Compatible), 2 x SPITM, and UART serial ports available concurrently Four general purpose 16-bit counter/timers Programmable 16-bit counter/timer array with six capture/compare modules and watchdog timer
Clock Sources - Internal oscillators: 24.5 MHz, 2% accuracy supports UART operation; 20 MHz low power oscillator requires very little bias current. External oscillator: Crystal, RC, C, or CMOS clock SmaRTClock oscillator: 32 kHz crystal or internal low frequency oscillator (`F912/02) or self-oscillate mode Can switch between clock sources on-the-fly; useful in implementing various power saving modes
On-Chip Debug - On-chip debug circuitry facilitates full-speed, nonintrusive in-system debug (no emulator required)
Two Comparators - Programmable hysteresis and response time - Configurable as wake-up or reset source - Up to 15 Capacitive Touch Sense Inputs 6-Bit Programmable Current Reference - Up to 500 A. Can be used as a bias or for generating a custom reference voltage PWM enhanced mode on `F912/02 devices
- Provides 4 breakpoints, single stepping - Inspect/modify memory and registers - Complete development kit Packages - 24-pin QFN (4 x 4 mm) - 24-pin QSOP (easy to hand-solder) - Tested die available Temperature Range: -40 to +85 C
ANALOG PERIPHERALS
A M U X
DIGITAL I/O
UART SMBus 2 x SPI PCA Timer 0 Timer 1 Timer 2 Timer 3 CRC Port 0 CROSSBAR
12/10-bit 75/300 ksps ADC
+
IREF
Port 1
+ -
TEMP SENSOR
VREF VREG
-
Port 2
VOLTAGE COMPARATORS
24.5 MHz PRECISION INTERNAL OSCILLATOR External Oscillator
20 MHz LOW POWER INTERNAL OSCILLATOR HARDW ARE SmaRTClock
HIGH-SPEED CONTROLLER CORE 16/8 kB ISP FLASH FLEXIBLE INTERRUPTS 8051 CPU (25 MIPS) DEBUG CIRCUITRY 768 B SRAM POR W DT
Rev. 1.0 9/10
Copyright (c) 2010 by Silicon Laboratories
C8051F91x-C8051F90x
C8051F91x-C8051F90x
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Table of Contents
1. System Overview.................................................................................................... 17 1.1. CIP-51TM Microcontroller Core.......................................................................... 20 1.1.1. Fully 8051 Compatible.............................................................................. 20 1.1.2. Improved Throughput ............................................................................... 20 1.1.3. Additional Features .................................................................................. 20 1.2. Port Input/Output............................................................................................... 21 1.3. Serial Ports ....................................................................................................... 22 1.4. Programmable Counter Array ........................................................................... 22 1.5. SAR ADC with 16-bit Auto-Averaging Accumulator and Autonomous Low Power Burst Mode ............................................................... 23 1.6. Programmable Current Reference (IREF0) ...................................................... 24 1.7. Comparators ..................................................................................................... 24 2. Ordering Information.............................................................................................. 26 3. Pinout and Package Definitions............................................................................ 27 4. Electrical Characteristics....................................................................................... 36 4.1. Absolute Maximum Specifications .................................................................... 36 4.2. Electrical Characteristics................................................................................... 37 5. SAR ADC with 16-bit Auto-Averaging Accumulator and Autonomous Low Power Burst Mode................................................................... 61 5.1. Output Code Formatting ................................................................................... 62 5.2. Modes of Operation .......................................................................................... 63 5.2.1. Starting a Conversion............................................................................... 63 5.2.2. Tracking Modes........................................................................................ 64 5.2.3. Burst Mode ............................................................................................... 65 5.2.4. Settling Time Requirements ..................................................................... 66 5.2.5. Gain Setting.............................................................................................. 67 5.3. 8-Bit Mode......................................................................................................... 67 5.4. 12-Bit Mode (C8051F912/02 Only) ................................................................... 67 5.5. Low Power Mode (C8051F912/902 only) ......................................................... 67 5.6. Programmable Window Detector ...................................................................... 75 5.6.1. Window Detector In Single-Ended Mode ................................................. 77 5.6.2. ADC0 Specifications................................................................................. 77 5.7. ADC0 Analog Multiplexer.................................................................................. 78 5.8. Temperature Sensor ......................................................................................... 80 5.8.1. Calibration ................................................................................................ 81 5.9. Voltage and Ground Reference Options........................................................... 83 5.10.External Voltage References............................................................................ 84 5.11.Internal Voltage References ............................................................................. 84 5.12.Analog Ground Reference................................................................................ 84 5.13.Temperature Sensor Enable ............................................................................ 84 5.14.Voltage Reference Electrical Specifications ..................................................... 85 6. Programmable Current Reference (IREF0) .......................................................... 86 6.1. PWM Enhanced Mode ...................................................................................... 86
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6.2. IREF0 Specifications......................................................................................... 87 7. Comparators ........................................................................................................... 88 7.1. Comparator Inputs ............................................................................................ 88 7.2. Comparator Outputs ......................................................................................... 89 7.3. Comparator Response Time............................................................................. 90 7.4. Comparator Hysteresis ..................................................................................... 90 7.5. Comparator Register Descriptions.................................................................... 91 7.6. Comparator0 and Comparator1 Analog Multiplexers........................................ 95 8. CIP-51 Microcontroller ........................................................................................... 98 8.1. Performance ..................................................................................................... 98 8.2. Programming and Debugging Support ............................................................. 99 8.3. Instruction Set ................................................................................................... 99 8.3.1. Instruction and CPU Timing ..................................................................... 99 8.4. CIP-51 Register Descriptions.......................................................................... 104 9. Memory Organization........................................................................................... 107 9.1. Program Memory ............................................................................................ 108 9.1.1. MOVX Instruction and Program Memory ............................................... 108 9.2. Data Memory .................................................................................................. 108 9.2.1. Internal RAM .......................................................................................... 108 9.2.2. External RAM ......................................................................................... 110 10. On-Chip XRAM...................................................................................................... 111 10.1.Accessing XRAM............................................................................................ 111 10.1.1.16-Bit MOVX Example ........................................................................... 111 10.1.2.8-Bit MOVX Example ............................................................................. 111 10.2.Special Function Registers............................................................................. 112 11. Special Function Registers ................................................................................. 113 11.1.SFR Paging .................................................................................................... 114 12. Interrupt Handler .................................................................................................. 120 12.1.Enabling Interrupt Sources ............................................................................. 120 12.2.MCU Interrupt Sources and Vectors............................................................... 120 12.3.Interrupt Priorities ........................................................................................... 121 12.4.Interrupt Latency............................................................................................. 121 12.5.Interrupt Register Descriptions ....................................................................... 123 12.6.External Interrupts INT0 and INT1.................................................................. 130 13. Flash Memory ....................................................................................................... 132 13.1.Programming The Flash Memory ................................................................... 132 13.1.1.Flash Lock and Key Functions ............................................................... 132 13.1.2.Flash Erase Procedure .......................................................................... 133 13.1.3.Flash Write Procedure ........................................................................... 133 13.2.Non-volatile Data Storage .............................................................................. 133 13.3.Security Options ............................................................................................. 134 13.4.Determining the Device Part Number at Run Time ........................................ 136 13.5.Flash Write and Erase Guidelines .................................................................. 137 13.5.1.VDD Maintenance and the VDD Monitor ............................................... 137 13.5.2.PSWE Maintenance ............................................................................... 138
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13.5.3.System Clock ......................................................................................... 138 13.6.Minimizing Flash Read Current ...................................................................... 139 14. Power Management.............................................................................................. 143 14.1.Normal Mode .................................................................................................. 144 14.2.Idle Mode........................................................................................................ 145 14.3.Stop Mode ...................................................................................................... 145 14.4.Suspend Mode ............................................................................................... 146 14.5.Sleep Mode .................................................................................................... 146 14.6.Configuring Wakeup Sources......................................................................... 147 14.7.Determining the Event that Caused the Last Wakeup.................................... 148 14.8.Power Management Specifications ................................................................ 151 15. Cyclic Redundancy Check Unit (CRC0) ............................................................. 152 15.1.CRC Algorithm................................................................................................ 152 15.2.Preparing for a CRC Calculation .................................................................... 154 15.3.Performing a CRC Calculation ....................................................................... 154 15.4.Accessing the CRC0 Result ........................................................................... 154 15.5.CRC0 Bit Reverse Feature............................................................................. 159 16. On-Chip DC-DC Converter (DC0) ........................................................................ 160 16.1.Startup Behavior............................................................................................. 161 16.2.High Power Applications ............................................................................. 162 16.3.Pulse Skipping Mode...................................................................................... 162 16.4.Enabling the DC-DC Converter ...................................................................... 163 16.5.Minimizing Power Supply Noise ..................................................................... 164 16.6.Selecting the Optimum Switch Size................................................................ 164 16.7.DC-DC Converter Clocking Options ............................................................... 164 16.8.DC-DC Converter Behavior in Sleep Mode .................................................... 164 16.9.Bypass Mode (C8051F912/02 only) ............................................................... 165 16.10.Low Power Mode (C8051F912/02 only) ....................................................... 165 16.11.Passive Diode Mode (C8051F912/02 only).................................................. 166 16.12.DC-DC Converter Register Descriptions ...................................................... 167 16.13.DC-DC Converter Specifications .................................................................. 169 17. Voltage Regulator (VREG0) ................................................................................. 170 17.1.Voltage Regulator Electrical Specifications .................................................... 170 18. Reset Sources....................................................................................................... 171 18.1.Power-On (VBAT Supply Monitor) Reset ....................................................... 172 18.2.Power-Fail (VDD/DC+ Supply Monitor) Reset................................................ 173 18.3.External Reset ................................................................................................ 176 18.4.Missing Clock Detector Reset ........................................................................ 176 18.5.Comparator0 Reset ........................................................................................ 176 18.6.PCA Watchdog Timer Reset .......................................................................... 176 18.7.Flash Error Reset ........................................................................................... 177 18.8.SmaRTClock (Real Time Clock) Reset .......................................................... 177 18.9.Software Reset ............................................................................................... 177 19. Clocking Sources ................................................................................................. 179 19.1.Programmable Precision Internal Oscillator ................................................... 180
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19.2.Low Power Internal Oscillator......................................................................... 180 19.3.External Oscillator Drive Circuit...................................................................... 180 19.3.1.External Crystal Mode............................................................................ 180 19.3.2.External RC Mode.................................................................................. 182 19.3.3.External Capacitor Mode........................................................................ 183 19.3.4.External CMOS Clock Mode .................................................................. 184 19.4.Special Function Registers for Selecting and Configuring the System Clock 185 20. SmaRTClock (Real Time Clock) .......................................................................... 188 20.1.SmaRTClock Interface ................................................................................... 189 20.1.1.SmaRTClock Lock and Key Functions................................................... 189 20.1.2.Using RTC0ADR and RTC0DAT to Access SmaRTClock Internal Registers ................................................................................... 190 20.1.3.RTC0ADR Short Strobe Feature............................................................ 190 20.1.4.SmaRTClock Interface Autoread Feature .............................................. 190 20.1.5.RTC0ADR Autoincrement Feature......................................................... 191 20.2.SmaRTClock Clocking Sources ..................................................................... 194 20.2.1.Using the SmaRTClock Oscillator with a Crystal or External CMOS Clock ............................................................................ 194 20.2.2.Using the SmaRTClock Oscillator in Self-Oscillate Mode...................... 195 20.2.3.Using the Low Frequency Oscillator (LFO) ............................................ 195 20.2.4.Programmable Load Capacitance.......................................................... 196 20.2.5.Automatic Gain Control (Crystal Mode Only) and SmaRTClock Bias Doubling ................................................................... 197 20.2.6.Missing SmaRTClock Detector .............................................................. 199 20.2.7.SmaRTClock Oscillator Crystal Valid Detector ...................................... 199 20.3.SmaRTClock Timer and Alarm Function ........................................................ 199 20.3.1.Setting and Reading the SmaRTClock Timer Value .............................. 199 20.3.2.Setting a SmaRTClock Alarm ................................................................ 200 20.3.3.Software Considerations for using the SmaRTClock Timer and Alarm . 200 21. Port Input/Output.................................................................................................. 205 21.1.Port I/O Modes of Operation........................................................................... 206 21.1.1.Port Pins Configured for Analog I/O....................................................... 206 21.1.2.Port Pins Configured For Digital I/O....................................................... 206 21.1.3.Interfacing Port I/O to 5 V and 3.3 V Logic............................................. 207 21.1.4.Increasing Port I/O Drive Strength ......................................................... 207 21.2.Assigning Port I/O Pins to Analog and Digital Functions................................ 207 21.2.1.Assigning Port I/O Pins to Analog Functions ......................................... 207 21.2.2.Assigning Port I/O Pins to Digital Functions........................................... 208 21.2.3.Assigning Port I/O Pins to External Digital Event Capture Functions .... 208 21.3.Priority Crossbar Decoder .............................................................................. 209 21.4.Port Match ...................................................................................................... 215 21.5.Special Function Registers for Accessing and Configuring Port I/O .............. 217 22. SMBus ................................................................................................................... 225 22.1.Supporting Documents ................................................................................... 226 22.2.SMBus Configuration...................................................................................... 226
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22.3.SMBus Operation ........................................................................................... 227 22.3.1.Transmitter Vs. Receiver........................................................................ 227 22.3.2.Arbitration............................................................................................... 227 22.3.3.Clock Low Extension.............................................................................. 228 22.3.4.SCL Low Timeout................................................................................... 228 22.3.5.SCL High (SMBus Free) Timeout .......................................................... 228 22.4.Using the SMBus............................................................................................ 229 22.4.1.SMBus Configuration Register............................................................... 230 22.4.2.SMB0CN Control Register ..................................................................... 233 22.4.3.Hardware Slave Address Recognition ................................................... 236 22.4.4.Data Register ......................................................................................... 238 22.5.SMBus Transfer Modes.................................................................................. 239 22.5.1.Write Sequence (Master) ....................................................................... 239 22.5.2.Read Sequence (Master) ....................................................................... 240 22.5.3.Write Sequence (Slave) ......................................................................... 241 22.5.4.Read Sequence (Slave) ......................................................................... 242 22.6.SMBus Status Decoding................................................................................. 242 23. UART0.................................................................................................................... 247 23.1.Enhanced Baud Rate Generation................................................................... 248 23.2.Operational Modes ......................................................................................... 249 23.2.1.8-Bit UART ............................................................................................. 249 23.2.2.9-Bit UART ............................................................................................. 250 23.3.Multiprocessor Communications .................................................................... 250 24. Enhanced Serial Peripheral Interface (SPI0 and SPI1)...................................... 255 24.1.Signal Descriptions......................................................................................... 256 24.1.1.Master Out, Slave In (MOSI).................................................................. 256 24.1.2.Master In, Slave Out (MISO).................................................................. 256 24.1.3.Serial Clock (SCK) ................................................................................. 256 24.1.4.Slave Select (NSS) ................................................................................ 256 24.2.SPI Master Mode Operation ........................................................................... 257 24.3.SPI Slave Mode Operation ............................................................................. 259 24.4.SPI Interrupt Sources ..................................................................................... 259 24.5.Serial Clock Phase and Polarity ..................................................................... 260 24.6.SPI Special Function Registers ...................................................................... 262 25. Timers.................................................................................................................... 270 25.1.Timer 0 and Timer 1 ....................................................................................... 272 25.1.1.Mode 0: 13-bit Counter/Timer ................................................................ 272 25.1.2.Mode 1: 16-bit Counter/Timer ................................................................ 273 25.1.3.Mode 2: 8-bit Counter/Timer with Auto-Reload...................................... 274 25.1.4.Mode 3: Two 8-bit Counter/Timers (Timer 0 Only)................................. 275 25.2.Timer 2 .......................................................................................................... 280 25.2.1.16-bit Timer with Auto-Reload................................................................ 280 25.2.2.8-bit Timers with Auto-Reload................................................................ 281 25.2.3.Comparator 0/SmaRTClock Capture Mode ........................................... 282 25.3.Timer 3 .......................................................................................................... 286
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25.3.1.16-bit Timer with Auto-Reload................................................................ 286 25.3.2.8-bit Timers with Auto-Reload................................................................ 287 25.3.3.Comparator 1/External Oscillator Capture Mode ................................... 288 26. Programmable Counter Array ............................................................................. 292 26.1.PCA Counter/Timer ........................................................................................ 293 26.2.PCA0 Interrupt Sources.................................................................................. 294 26.3.Capture/Compare Modules ............................................................................ 296 26.3.1.Edge-triggered Capture Mode................................................................ 297 26.3.2.Software Timer (Compare) Mode........................................................... 298 26.3.3.High-Speed Output Mode ...................................................................... 299 26.3.4.Frequency Output Mode ........................................................................ 300 26.3.5. 8-Bit, 9-Bit, 10-Bit and 11-Bit Pulse Width Modulator Modes............... 301 26.3.6. 16-Bit Pulse Width Modulator Mode..................................................... 303 26.4.Watchdog Timer Mode ................................................................................... 304 26.4.1.Watchdog Timer Operation .................................................................... 304 26.4.2.Watchdog Timer Usage ......................................................................... 305 26.5.Register Descriptions for PCA0...................................................................... 306 27. C2 Interface ........................................................................................................... 312 27.1.C2 Interface Registers.................................................................................... 312 27.2.C2 Pin Sharing ............................................................................................... 315 Document Change List............................................................................................. 316 Contact Information.................................................................................................. 318
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List of Figures
Figure 1.1. C8051F912 Block Diagram .................................................................... 18 Figure 1.2. C8051F911 Block Diagram .................................................................... 18 Figure 1.3. C8051F902 Block Diagram .................................................................... 19 Figure 1.4. C8051F901 Block Diagram .................................................................... 19 Figure 1.5. Port I/O Functional Block Diagram ......................................................... 21 Figure 1.6. PCA Block Diagram................................................................................ 22 Figure 1.7. ADC0 Functional Block Diagram............................................................ 23 Figure 1.8. ADC0 Multiplexer Block Diagram ........................................................... 24 Figure 1.9. Comparator 0 Functional Block Diagram ............................................... 25 Figure 1.10. Comparator 1 Functional Block Diagram ............................................. 25 Figure 3.1. QFN-24 Pinout Diagram (Top View) ...................................................... 30 Figure 3.2. QSOP-24 Pinout Diagram F912 (Top View) .......................................... 31 Figure 3.3. QFN-24 Package Drawing ..................................................................... 32 Figure 3.4. Typical QFN-24 Landing Diagram.......................................................... 33 Figure 3.5. QSOP-24 Package Diagram .................................................................. 34 Figure 3.6. QSOP-24 Landing Diagram ................................................................... 35 Figure 4.1. Active Mode Current (External CMOS Clock) ........................................ 41 Figure 4.2. Idle Mode Current (External CMOS Clock) ............................................ 42 Figure 4.3. Typical DC-DC Converter Efficiency (High Current, VDD/DC+ = 2 V) ... 43 Figure 4.4. Typical DC-DC Converter Efficiency (High Current, VDD/DC+ = 3 V) ... 44 Figure 4.5. Typical DC-DC Converter Efficiency (Low Current, VDD/DC+ = 2 V).... 45 Figure 4.6. Typical One-Cell Suspend Mode Current............................................... 46 Figure 4.7. Typical VOH Curves, 1.8-3.6 V ............................................................. 48 Figure 4.8. Typical VOH Curves, 0.9-1.8 V ............................................................. 49 Figure 4.9. Typical VOL Curves, 1.8-3.6 V .............................................................. 50 Figure 4.10. Typical VOL Curves, 0.9-1.8 V ............................................................ 51 Figure 5.1. ADC0 Functional Block Diagram............................................................ 61 Figure 5.2. 10-Bit ADC Track and Conversion Example Timing (BURSTEN = 0).... 64 Figure 5.3. Burst Mode Tracking Example with Repeat Count Set to 4 ................... 65 Figure 5.4. ADC0 Equivalent Input Circuits .............................................................. 66 Figure 5.5. ADC Window Compare Example: Right-Justified Single-Ended Data ... 77 Figure 5.6. ADC Window Compare Example: Left-Justified Single-Ended Data...... 77 Figure 5.7. ADC0 Multiplexer Block Diagram ........................................................... 78 Figure 5.8. Temperature Sensor Transfer Function ................................................. 80 Figure 5.9. Temperature Sensor Error with 1-Point Calibration (VREF = 1.68 V) ..... 81 Figure 5.10. Voltage Reference Functional Block Diagram...................................... 83 Figure 7.1. Comparator 0 Functional Block Diagram ............................................... 88 Figure 7.2. Comparator 1 Functional Block Diagram ............................................... 89 Figure 7.3. Comparator Hysteresis Plot ................................................................... 90 Figure 7.4. CPn Multiplexer Block Diagram.............................................................. 95 Figure 8.1. CIP-51 Block Diagram............................................................................ 98 Figure 9.1. C8051F91x-C8051F90x Memory Map ................................................. 107 Figure 9.2. Flash Program Memory Map................................................................ 108
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Figure 13.1. Flash Program Memory Map (16 kB and 8 kB devices)..................... 134 Figure 14.1. C8051F91x-C8051F90x Power Distribution....................................... 144 Figure 15.1. CRC0 Block Diagram ......................................................................... 152 Figure 15.2. Bit Reverse Register .......................................................................... 159 Figure 16.1. DC-DC Converter Block Diagram....................................................... 160 Figure 16.2. DC-DC Converter Configuration Options ........................................... 163 Figure 18.1. Reset Sources.................................................................................... 171 Figure 18.2. Power-Fail Reset Timing Diagram ..................................................... 172 Figure 18.3. Power-Fail Reset Timing Diagram ..................................................... 173 Figure 19.1. Clocking Sources Block Diagram ....................................................... 179 Figure 19.2. 25 MHz External Crystal Example...................................................... 181 Figure 20.1. SmaRTClock Block Diagram.............................................................. 188 Figure 20.2. Interpreting Oscillation Robustness (Duty Cycle) Test Results.......... 197 Figure 21.1. Port I/O Functional Block Diagram ..................................................... 205 Figure 21.2. Port I/O Cell Block Diagram ............................................................... 206 Figure 21.3. Crossbar Priority Decoder with No Pins Skipped ............................... 210 Figure 21.4. Crossbar Priority Decoder with Crystal Pins Skipped ........................ 211 Figure 22.1. SMBus Block Diagram ....................................................................... 225 Figure 22.2. Typical SMBus Configuration ............................................................. 226 Figure 22.3. SMBus Transaction ............................................................................ 227 Figure 22.4. Typical SMBus SCL Generation......................................................... 230 Figure 22.5. Typical Master Write Sequence ......................................................... 239 Figure 22.6. Typical Master Read Sequence ......................................................... 240 Figure 22.7. Typical Slave Write Sequence ........................................................... 241 Figure 22.8. Typical Slave Read Sequence ........................................................... 242 Figure 23.1. UART0 Block Diagram ....................................................................... 247 Figure 23.2. UART0 Baud Rate Logic .................................................................... 248 Figure 23.3. UART Interconnect Diagram .............................................................. 249 Figure 23.4. 8-Bit UART Timing Diagram............................................................... 249 Figure 23.5. 9-Bit UART Timing Diagram............................................................... 250 Figure 23.6. UART Multi-Processor Mode Interconnect Diagram .......................... 251 Figure 24.1. SPI Block Diagram ............................................................................. 255 Figure 24.2. Multiple-Master Mode Connection Diagram ....................................... 258 Figure 24.3. 3-Wire Single Master and 3-Wire Single Slave Mode Connection Diagram ........................................................................... 258 Figure 24.4. 4-Wire Single Master Mode and 4-Wire Slave Mode Connection Diagram........................................................................... 258 Figure 24.5. Master Mode Data/Clock Timing ........................................................ 260 Figure 24.6. Slave Mode Data/Clock Timing (CKPHA = 0) .................................... 261 Figure 24.7. Slave Mode Data/Clock Timing (CKPHA = 1) .................................... 261 Figure 24.8. SPI Master Timing (CKPHA = 0)........................................................ 267 Figure 24.9. SPI Master Timing (CKPHA = 1)........................................................ 267 Figure 24.10. SPI Slave Timing (CKPHA = 0)........................................................ 268 Figure 24.11. SPI Slave Timing (CKPHA = 1)........................................................ 268 Figure 25.1. T0 Mode 0 Block Diagram.................................................................. 273
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Figure 25.2. T0 Mode 2 Block Diagram.................................................................. 274 Figure 25.3. T0 Mode 3 Block Diagram.................................................................. 275 Figure 25.4. Timer 2 16-Bit Mode Block Diagram .................................................. 280 Figure 25.5. Timer 2 8-Bit Mode Block Diagram .................................................... 281 Figure 25.6. Timer 2 Capture Mode Block Diagram ............................................... 282 Figure 25.7. Timer 3 16-Bit Mode Block Diagram .................................................. 286 Figure 25.8. Timer 3 8-Bit Mode Block Diagram. ................................................... 287 Figure 25.9. Timer 3 Capture Mode Block Diagram ............................................... 288 Figure 26.1. PCA Block Diagram............................................................................ 292 Figure 26.2. PCA Counter/Timer Block Diagram.................................................... 294 Figure 26.3. PCA Interrupt Block Diagram ............................................................. 295 Figure 26.4. PCA Capture Mode Diagram.............................................................. 297 Figure 26.5. PCA Software Timer Mode Diagram .................................................. 298 Figure 26.6. PCA High-Speed Output Mode Diagram............................................ 299 Figure 26.7. PCA Frequency Output Mode ............................................................ 300 Figure 26.8. PCA 8-Bit PWM Mode Diagram ......................................................... 301 Figure 26.9. PCA 9, 10 and 11-Bit PWM Mode Diagram ....................................... 302 Figure 26.10. PCA 16-Bit PWM Mode.................................................................... 303 Figure 26.11. PCA Module 5 with Watchdog Timer Enabled ................................. 304 Figure 27.1. Typical C2 Pin Sharing....................................................................... 315
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List of Tables
2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Table 2.1. Product Selection Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Table 3.1. Pin Definitions for the C8051F91x-C8051F90x . . . . . . . . . . . . . . . . . . . 27 Table 3.2. QFN-24 Package Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Table 3.3. PCB Land Pattern ................................................................................... 33 Table 3.4. QSOP-24 Package Dimensions ............................................................. 34 Table 3.5. PCB Land Pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Table 4.1. Absolute Maximum Ratings .................................................................... 36 Table 4.2. Global Electrical Characteristics ............................................................. 37 Table 4.3. Port I/O DC Electrical Characteristics ..................................................... 47 Table 4.4. Reset Electrical Characteristics .............................................................. 52 Table 4.5. Power Management Electrical Specifications ......................................... 53 Table 4.6. Flash Electrical Characteristics .............................................................. 53 Table 4.7. Internal Precision Oscillator Electrical Characteristics ........................... 53 Table 4.8. Internal Low-Power Oscillator Electrical Characteristics ........................ 53 Table 4.9. SmaRTClock Characteristics .................................................................. 54 Table 4.10. ADC0 Electrical Characteristics ............................................................ 54 Table 4.11. Temperature Sensor Electrical Characteristics .................................... 55 Table 4.12. Voltage Reference Electrical Characteristics ....................................... 56 Table 4.13. IREF0 Electrical Characteristics ........................................................... 57 Table 4.14. Comparator Electrical Characteristics .................................................. 58 Table 4.15. VREG0 Electrical Characteristics ......................................................... 59 Table 4.16. DC-DC Converter (DC0) Electrical Characteristics .............................. 60 Table 5.1. Representative Conversion Times and Energy Consumption for the SAR ADC with 1.65 V High-Speed VREF . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 Table 8.1. CIP-51 Instruction Set Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 Table 11.1. Special Function Register (SFR) Memory Map (Page 0x0) . . . . . . . . 113 Table 11.2. Special Function Register (SFR) Memory Map (Page 0xF) . . . . . . . . 114 Table 11.3. Special Function Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 Table 12.1. Interrupt Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122 Table 13.1. Flash Security Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 Table 14.1. Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 Table 15.1. Example 16-bit CRC Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 Table 16.1. IPeak Inductor Current Limit Settings . . . . . . . . . . . . . . . . . . . . . . . . . 161 Table 19.1. Recommended XFCN Settings for Crystal Mode . . . . . . . . . . . . . . . . 181 Table 19.2. Recommended XFCN Settings for RC and C modes . . . . . . . . . . . . . 182 Table 20.1. SmaRTClock Internal Registers ......................................................... 189 Table 20.2. SmaRTClock Load Capacitance Settings . . . . . . . . . . . . . . . . . . . . . 196 Table 20.3. SmaRTClock Bias Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198 Table 21.1. Port I/O Assignment for Analog Functions . . . . . . . . . . . . . . . . . . . . . 207 Table 21.2. Port I/O Assignment for Digital Functions . . . . . . . . . . . . . . . . . . . . . . 208 Table 21.3. Port I/O Assignment for External Digital Event Capture Functions . . 208 Table 22.1. SMBus Clock Source Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
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Table 22.2. Minimum SDA Setup and Hold Times . . . . . . . . . . . . . . . . . . . . . . . . 231 Table 22.3. Sources for Hardware Changes to SMB0CN . . . . . . . . . . . . . . . . . . . 235 Table 22.4. Hardware Address Recognition Examples (EHACK = 1) . . . . . . . . . . 236 Table 22.5. SMBus Status Decoding With Hardware ACK Generation Disabled (EHACK = 0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243 Table 22.6. SMBus Status Decoding With Hardware ACK Generation Enabled (EHACK = 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 Table 23.1. Timer Settings for Standard Baud Rates Using The Internal 24.5 MHz Oscillator . . . . . . . . . . . . . . . . . . . . . . . 254 Table 23.2. Timer Settings for Standard Baud Rates Using an External 22.1184 MHz Oscillator . . . . . . . . . . . . . . . . . . . . . 254 Table 24.1. SPI Slave Timing Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269 Table 25.1. Timer 0 Running Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272 Table 26.1. PCA Timebase Input Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 Table 26.2. PCA0CPM and PCA0PWM Bit Settings for PCA Capture/Compare Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296 Table 26.3. Watchdog Timer Timeout Intervals . . . . . . . . . . . . . . . . . . . . . . . . . . . 305
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List of Registers
SFR Definition 5.1. ADC0CN: ADC0 Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 SFR Definition 5.2. ADC0CF: ADC0 Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 SFR Definition 5.3. ADC0AC: ADC0 Accumulator Configuration . . . . . . . . . . . . . . . . . 71 SFR Definition 5.4. ADC0PWR: ADC0 Burst Mode Power-Up Time . . . . . . . . . . . . . . 72 SFR Definition 5.5. ADC0TK: ADC0 Burst Mode Track Time . . . . . . . . . . . . . . . . . . . . 73 SFR Definition 5.6. ADC0H: ADC0 Data Word High Byte . . . . . . . . . . . . . . . . . . . . . . 74 SFR Definition 5.7. ADC0L: ADC0 Data Word Low Byte . . . . . . . . . . . . . . . . . . . . . . . 74 SFR Definition 5.8. ADC0GTH: ADC0 Greater-Than High Byte . . . . . . . . . . . . . . . . . . 75 SFR Definition 5.9. ADC0GTL: ADC0 Greater-Than Low Byte . . . . . . . . . . . . . . . . . . 75 SFR Definition 5.10. ADC0LTH: ADC0 Less-Than High Byte . . . . . . . . . . . . . . . . . . . 76 SFR Definition 5.11. ADC0LTL: ADC0 Less-Than Low Byte . . . . . . . . . . . . . . . . . . . . 76 SFR Definition 5.12. ADC0MX: ADC0 Input Channel Select . . . . . . . . . . . . . . . . . . . . 79 SFR Definition 5.13. TOFFH: ADC0 Data Word High Byte . . . . . . . . . . . . . . . . . . . . . 82 SFR Definition 5.14. TOFFL: ADC0 Data Word Low Byte . . . . . . . . . . . . . . . . . . . . . . 82 SFR Definition 5.15. REF0CN: Voltage Reference Control . . . . . . . . . . . . . . . . . . . . . 85 SFR Definition 6.1. IREF0CN: Current Reference Control . . . . . . . . . . . . . . . . . . . . . . 86 SFR Definition 6.2. IREF0CF: Current Reference Configuration . . . . . . . . . . . . . . . . . 87 SFR Definition 7.1. CPT0CN: Comparator 0 Control . . . . . . . . . . . . . . . . . . . . . . . . . . 91 SFR Definition 7.2. CPT0MD: Comparator 0 Mode Selection . . . . . . . . . . . . . . . . . . . 92 SFR Definition 7.3. CPT1CN: Comparator 1 Control . . . . . . . . . . . . . . . . . . . . . . . . . . 93 SFR Definition 7.4. CPT1MD: Comparator 1 Mode Selection . . . . . . . . . . . . . . . . . . . 94 SFR Definition 7.5. CPT0MX: Comparator0 Input Channel Select . . . . . . . . . . . . . . . . 96 SFR Definition 7.6. CPT1MX: Comparator1 Input Channel Select . . . . . . . . . . . . . . . . 97 SFR Definition 8.1. DPL: Data Pointer Low Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 SFR Definition 8.2. DPH: Data Pointer High Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 SFR Definition 8.3. SP: Stack Pointer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 SFR Definition 8.4. ACC: Accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 SFR Definition 8.5. B: B Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 SFR Definition 8.6. PSW: Program Status Word . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 SFR Definition 10.1. EMI0CN: External Memory Interface Control . . . . . . . . . . . . . . 112 SFR Definition 11.1. SFR Page: SFR Page . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 SFR Definition 12.1. IE: Interrupt Enable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 SFR Definition 12.2. IP: Interrupt Priority . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 SFR Definition 12.3. EIE1: Extended Interrupt Enable 1 . . . . . . . . . . . . . . . . . . . . . . 126 SFR Definition 12.4. EIP1: Extended Interrupt Priority 1 . . . . . . . . . . . . . . . . . . . . . . 127 SFR Definition 12.5. EIE2: Extended Interrupt Enable 2 . . . . . . . . . . . . . . . . . . . . . . 128 SFR Definition 12.6. EIP2: Extended Interrupt Priority 2 . . . . . . . . . . . . . . . . . . . . . . 129 SFR Definition 12.7. IT01CF: INT0/INT1 Configuration . . . . . . . . . . . . . . . . . . . . . . . 131 SFR Definition 13.1. PSCTL: Program Store R/W Control . . . . . . . . . . . . . . . . . . . . . 140 SFR Definition 13.2. FLKEY: Flash Lock and Key . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 SFR Definition 13.3. FLSCL: Flash Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 SFR Definition 13.4. FLWR: Flash Write Only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 SFR Definition 14.1. PMU0CF: Power Management Unit Configuration1,2 . . . . . . . . 149
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SFR Definition 14.2. PMU0MD: Power Management Unit Mode . . . . . . . . . . . . . . . . 150 SFR Definition 14.3. PCON: Power Management Control Register . . . . . . . . . . . . . . 151 SFR Definition 15.1. CRC0CN: CRC0 Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 SFR Definition 15.2. CRC0IN: CRC0 Data Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156 SFR Definition 15.3. CRC0DAT: CRC0 Data Output . . . . . . . . . . . . . . . . . . . . . . . . . 156 SFR Definition 15.4. CRC0AUTO: CRC0 Automatic Control . . . . . . . . . . . . . . . . . . . 157 SFR Definition 15.5. CRC0CNT: CRC0 Automatic Flash Sector Count . . . . . . . . . . . 158 SFR Definition 15.6. CRC0FLIP: CRC0 Bit Flip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159 SFR Definition 16.1. DC0CN: DC-DC Converter Control . . . . . . . . . . . . . . . . . . . . . . 167 SFR Definition 16.2. DC0CF: DC-DC Converter Configuration . . . . . . . . . . . . . . . . . 168 SFR Definition 16.3. DC0MD: DC-DC Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 SFR Definition 17.1. REG0CN: Voltage Regulator Control . . . . . . . . . . . . . . . . . . . . 170 SFR Definition 18.1. VDM0CN: VDD/DC+ Supply Monitor Control . . . . . . . . . . . . . . 175 SFR Definition 18.2. RSTSRC: Reset Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 SFR Definition 19.1. CLKSEL: Clock Select . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 SFR Definition 19.2. OSCICN: Internal Oscillator Control . . . . . . . . . . . . . . . . . . . . . 186 SFR Definition 19.3. OSCICL: Internal Oscillator Calibration . . . . . . . . . . . . . . . . . . . 186 SFR Definition 19.4. OSCXCN: External Oscillator Control . . . . . . . . . . . . . . . . . . . . 187 SFR Definition 20.1. RTC0KEY: SmaRTClock Lock and Key . . . . . . . . . . . . . . . . . . 192 SFR Definition 20.2. RTC0ADR: SmaRTClock Address . . . . . . . . . . . . . . . . . . . . . . 193 SFR Definition 20.3. RTC0DAT: SmaRTClock Data . . . . . . . . . . . . . . . . . . . . . . . . . 193 Internal Register Definition 20.4. RTC0CN: SmaRTClock Control . . . . . . . . . . . . . . . 201 Internal Register Definition 20.5. RTC0XCN: SmaRTClock Oscillator Control . . . . . . 202 Internal Register Definition 20.6. RTC0XCF: SmaRTClock Oscillator Configuration . 203 Internal Register Definition 20.7. RTC0PIN: SmaRTClock Pin Configuration . . . . . . 203 Internal Register Definition 20.8. CAPTUREn: SmaRTClock Timer Capture . . . . . . . 204 Internal Register Definition 20.9. ALARMn: SmaRTClock Alarm Programmed Value 204 SFR Definition 21.1. XBR0: Port I/O Crossbar Register 0 . . . . . . . . . . . . . . . . . . . . . 212 SFR Definition 21.2. XBR1: Port I/O Crossbar Register 1 . . . . . . . . . . . . . . . . . . . . . 213 SFR Definition 21.3. XBR2: Port I/O Crossbar Register 2 . . . . . . . . . . . . . . . . . . . . . 214 SFR Definition 21.4. P0MASK: Port0 Mask Register . . . . . . . . . . . . . . . . . . . . . . . . . 215 SFR Definition 21.5. P0MAT: Port0 Match Register . . . . . . . . . . . . . . . . . . . . . . . . . . 215 SFR Definition 21.6. P1MASK: Port1 Mask Register . . . . . . . . . . . . . . . . . . . . . . . . . 216 SFR Definition 21.7. P1MAT: Port1 Match Register . . . . . . . . . . . . . . . . . . . . . . . . . . 216 SFR Definition 21.8. P0: Port0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218 SFR Definition 21.9. P0SKIP: Port0 Skip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218 SFR Definition 21.10. P0MDIN: Port0 Input Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 SFR Definition 21.11. P0MDOUT: Port0 Output Mode . . . . . . . . . . . . . . . . . . . . . . . . 219 SFR Definition 21.12. P0DRV: Port0 Drive Strength . . . . . . . . . . . . . . . . . . . . . . . . . 220 SFR Definition 21.13. P1: Port1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221 SFR Definition 21.14. P1SKIP: Port1 Skip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221 SFR Definition 21.15. P1MDIN: Port1 Input Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . 222 SFR Definition 21.16. P1MDOUT: Port1 Output Mode . . . . . . . . . . . . . . . . . . . . . . . . 222 SFR Definition 21.17. P1DRV: Port1 Drive Strength . . . . . . . . . . . . . . . . . . . . . . . . . 223 SFR Definition 21.18. P2: Port2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
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SFR Definition 21.19. P2MDOUT: Port2 Output Mode . . . . . . . . . . . . . . . . . . . . . . . . 224 SFR Definition 21.20. P2DRV: Port2 Drive Strength . . . . . . . . . . . . . . . . . . . . . . . . . 224 SFR Definition 22.1. SMB0CF: SMBus Clock/Configuration . . . . . . . . . . . . . . . . . . . 232 SFR Definition 22.2. SMB0CN: SMBus Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234 SFR Definition 22.3. SMB0ADR: SMBus Slave Address . . . . . . . . . . . . . . . . . . . . . . 237 SFR Definition 22.4. SMB0ADM: SMBus Slave Address Mask . . . . . . . . . . . . . . . . . 237 SFR Definition 22.5. SMB0DAT: SMBus Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238 SFR Definition 23.1. SCON0: Serial Port 0 Control . . . . . . . . . . . . . . . . . . . . . . . . . . 252 SFR Definition 23.2. SBUF0: Serial (UART0) Port Data Buffer . . . . . . . . . . . . . . . . . 253 SFR Definition 24.1. SPInCFG: SPI Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . 263 SFR Definition 24.2. SPInCN: SPI Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264 SFR Definition 24.3. SPInCKR: SPI Clock Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265 SFR Definition 24.4. SPInDAT: SPI Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266 SFR Definition 25.1. CKCON: Clock Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271 SFR Definition 25.2. TCON: Timer Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276 SFR Definition 25.3. TMOD: Timer Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277 SFR Definition 25.4. TL0: Timer 0 Low Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278 SFR Definition 25.5. TL1: Timer 1 Low Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278 SFR Definition 25.6. TH0: Timer 0 High Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279 SFR Definition 25.7. TH1: Timer 1 High Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279 SFR Definition 25.8. TMR2CN: Timer 2 Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283 SFR Definition 25.9. TMR2RLL: Timer 2 Reload Register Low Byte . . . . . . . . . . . . . 284 SFR Definition 25.10. TMR2RLH: Timer 2 Reload Register High Byte . . . . . . . . . . . 284 SFR Definition 25.11. TMR2L: Timer 2 Low Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 SFR Definition 25.12. TMR2H Timer 2 High Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 SFR Definition 25.13. TMR3CN: Timer 3 Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 SFR Definition 25.14. TMR3RLL: Timer 3 Reload Register Low Byte . . . . . . . . . . . . 290 SFR Definition 25.15. TMR3RLH: Timer 3 Reload Register High Byte . . . . . . . . . . . 290 SFR Definition 25.16. TMR3L: Timer 3 Low Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291 SFR Definition 25.17. TMR3H Timer 3 High Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291 SFR Definition 26.1. PCA0CN: PCA Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306 SFR Definition 26.2. PCA0MD: PCA Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307 SFR Definition 26.3. PCA0PWM: PCA PWM Configuration . . . . . . . . . . . . . . . . . . . . 308 SFR Definition 26.4. PCA0CPMn: PCA Capture/Compare Mode . . . . . . . . . . . . . . . 309 SFR Definition 26.5. PCA0L: PCA Counter/Timer Low Byte . . . . . . . . . . . . . . . . . . . 310 SFR Definition 26.6. PCA0H: PCA Counter/Timer High Byte . . . . . . . . . . . . . . . . . . . 310 SFR Definition 26.7. PCA0CPLn: PCA Capture Module Low Byte . . . . . . . . . . . . . . . 311 SFR Definition 26.8. PCA0CPHn: PCA Capture Module High Byte . . . . . . . . . . . . . . 311 C2 Register Definition 27.1. C2ADD: C2 Address . . . . . . . . . . . . . . . . . . . . . . . . . . . 312 C2 Register Definition 27.2. DEVICEID: C2 Device ID . . . . . . . . . . . . . . . . . . . . . . . . 313 C2 Register Definition 27.3. REVID: C2 Revision ID . . . . . . . . . . . . . . . . . . . . . . . . . 313 C2 Register Definition 27.4. FPCTL: C2 Flash Programming Control . . . . . . . . . . . . 314 C2 Register Definition 27.5. FPDAT: C2 Flash Programming Data . . . . . . . . . . . . . . 314
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1. System Overview
C8051F91x-C8051F90x devices are fully integrated mixed-signal System-on-a-Chip MCUs. Highlighted features are listed below. Refer to Table 2.1 for specific product feature selection and part ordering numbers. * * * * * * * * * * * * * * Single/Dual Battery operation with on-chip dc-dc boost converter. High-speed pipelined 8051-compatible microcontroller core (up to 25 MIPS) In-system, full-speed, non-intrusive debug interface (on-chip) 10-bit 300 ksps or 12-bit 75 ksps single-ended ADC with analog multiplexer 6-Bit Programmable Current Reference. Resolution can be increased with PWM. Precision programmable 24.5 MHz internal oscillator with spread spectrum technology. 16 kB or 8 kB of on-chip Flash memory 768 bytes of on-chip RAM SMBus/I2C, Enhanced UART, and two Enhanced SPI serial interfaces implemented in hardware Four general-purpose 16-bit timers Programmable Counter/Timer Array (PCA) with six capture/compare modules and Watchdog Timer function On-chip Power-On Reset, VDD Monitor, and Temperature Sensor Two On-chip Voltage Comparators with 15 Capacitive Touch Sense inputs. 16 Port I/O (5 V tolerant)
With on-chip Power-On Reset, VDD monitor, Watchdog Timer, and clock oscillator, the C8051F91xC8051F90x devices are truly stand-alone System-on-a-Chip solutions. The Flash memory can be reprogrammed even in-circuit, providing non-volatile data storage, and also allowing field upgrades of the 8051 firmware. User software has complete control of all peripherals, and may individually shut down any or all peripherals for power savings. The on-chip Silicon Labs 2-Wire (C2) Development Interface allows non-intrusive (uses no on-chip resources), full speed, in-circuit debugging using the production MCU installed in the final application. This debug logic supports inspection and modification of memory and registers, setting breakpoints, single stepping, run and halt commands. All analog and digital peripherals are fully functional while debugging using C2. The two C2 interface pins can be shared with user functions, allowing in-system debugging without occupying package pins. Each device is specified for 0.9 to 1.8 V, 0.9 to 3.6 V or 1.8 to 3.6 V operation over the industrial temperature range (-40 to +85 C). The Port I/O and RST pins are tolerant of input signals up to 5 V. The C8051F91x-C8051F90x devices are available in 24-pin QFN or QSOP packages. Both package options are lead-free and RoHS compliant. See Table 2.1for ordering information. Block diagrams are included in Figure 1.1 through Figure 1.4.
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CIP-51 8051 Controller Core
16k Byte ISP Flash Program Memory 256 Byte SRAM 512 Byte XRAM Port I/O Configuration
Power On Reset/PMU
Wake Reset
Digital Peripherals
UART Timers 0, 1, 2, 3 PCA/ WDT SMBus SPI 0,1 Crossbar Control Port 1 Drivers Priority Crossbar Decoder Port 0 Drivers
C2CK/RST
Debug / Programming Hardware C2D
P0.0/VREF P0.1/AGND P0.2/XTAL1/RTCOUT P0.3/XTAL2/WAKEOUT P0.4/TX P0.5/RX P0.6/CNVSTR P0.7/IREF0 P1.0 P1.1 P1.2 P1.3 P1.4 P1.5 P1.6
VDD/DC+ GND/DC-
Power Net Analog Power
VREG
CRC Engine
Digital Power SYSCLK
Precision 24.5 MHz Oscillator DC/DC Converter Low Power 20 MHz Oscillator External Oscillator Circuit SmaRTClock Oscillator
SFR Bus
Analog Peripherals
6-bit IREF
Internal External VREF A M U X VDD VREF Temp Sensor GND CP0, CP0A CP1, CP1A
+ -
DCEN VBAT GND
IREF0
Port 2 Drivers
XTAL1 XTAL2 XTAL3 XTAL4
VREF
12/10-bit 75/300ksps ADC
P2.7/C2D
System Clock Configuration
+ -
Comparators
Figure 1.1. C8051F912 Block Diagram
Power On Reset/PMU
Wake Reset
CIP-51 8051 Controller Core
16k Byte ISP Flash Program Memory 256 Byte SRAM 512 Byte XRAM
Port I/O Configuration
Digital Peripherals
UART Timers 0, 1, 2, 3 PCA/ WDT SMBus SPI 0,1 Crossbar Control Port 1 Drivers Priority Crossbar Decoder Port 0 Drivers
C2CK/RST
Debug / Programming Hardware C2D
P0.0/VREF P0.1/AGND P0.2/XTAL1 P0.3/XTAL2 P0.4/TX P0.5/RX P0.6/CNVSTR P0.7/IREF0 P1.0 P1.1 P1.2 P1.3 P1.4 P1.5 P1.6
VDD/DC+ GND/DC-
Power Net Analog Power
VREG
CRC Engine
Digital Power SYSCLK
Precision 24.5 MHz Oscillator DC/DC Converter Low Power 20 MHz Oscillator External Oscillator Circuit SmaRTClock Oscillator
SFR Bus
Analog Peripherals
6-bit IREF
Internal External VREF A M U X VDD VREF Temp Sensor GND CP0, CP0A CP1, CP1A
+ -
DCEN VBAT GND
IREF0
Port 2 Drivers
XTAL1 XTAL2 XTAL3 XTAL4
VREF
10-bit 300ksps ADC
P2.7/C2D
System Clock Configuration
+ -
Comparators
Figure 1.2. C8051F911 Block Diagram
18
Rev. 1.0
C8051F91x-C8051F90x
Port I/O Configuration
Power On Reset/PMU
Wake Reset
CIP-51 8051 Controller Core
8k Byte ISP Flash Program Memory 256 Byte SRAM 512 Byte XRAM
Digital Peripherals
UART Timers 0, 1, 2, 3 PCA/ WDT SMBus SPI 0,1 Crossbar Control Port 1 Drivers Priority Crossbar Decoder Port 0 Drivers
C2CK/RST
Debug / Programming Hardware C2D
P0.0/VREF P0.1/AGND P0.2/XTAL1/RTCOUT P0.3/XTAL2/WAKEOUT P0.4/TX P0.5/RX P0.6/CNVSTR P0.7/IREF0 P1.0 P1.1 P1.2 P1.3 P1.4 P1.5 P1.6
VDD/DC+ GND/DC-
Power Net Analog Power
VREG
CRC Engine
Digital Power SYSCLK
Precision 24.5 MHz Oscillator DC/DC Converter Low Power 20 MHz Oscillator External Oscillator Circuit SmaRTClock Oscillator
SFR Bus
Analog Peripherals
6-bit IREF
Internal External VREF A M U X VDD VREF Temp Sensor GND CP0, CP0A CP1, CP1A
+ -
DCEN VBAT GND
IREF0
Port 2 Drivers
XTAL1 XTAL2 XTAL3 XTAL4
VREF
12/10-bit 75/300ksps ADC
P2.7/C2D
System Clock Configuration
+ -
Comparators
Figure 1.3. C8051F902 Block Diagram
Power On Reset/PMU
Wake Reset
CIP-51 8051 Controller Core
8k Byte ISP Flash Program Memory 256 Byte SRAM 512 Byte XRAM
Port I/O Configuration
Digital Peripherals
UART Timers 0, 1, 2, 3 PCA/ WDT SMBus SPI 0,1 Crossbar Control Port 1 Drivers Priority Crossbar Decoder Port 0 Drivers
C2CK/RST
Debug / Programming Hardware C2D
P0.0/VREF P0.1/AGND P0.2/XTAL1 P0.3/XTAL2 P0.4/TX P0.5/RX P0.6/CNVSTR P0.7/IREF0 P1.0 P1.1 P1.2 P1.3 P1.4 P1.5 P1.6
VDD/DC+ GND/DC-
Power Net Analog Power
VREG
CRC Engine
Digital Power SYSCLK
Precision 24.5 MHz Oscillator DC/DC Converter Low Power 20 MHz Oscillator External Oscillator Circuit SmaRTClock Oscillator
SFR Bus
Analog Peripherals
6-bit IREF
Internal External VREF A M U X VDD VREF Temp Sensor GND CP0, CP0A CP1, CP1A
+ -
DCEN VBAT GND
IREF0
Port 2 Drivers
XTAL1 XTAL2 XTAL3 XTAL4
VREF
10-bit 300ksps ADC
P2.7/C2D
System Clock Configuration
+ -
Comparators
Figure 1.4. C8051F901 Block Diagram
Rev. 1.0
19
C8051F91x-C8051F90x
1.1. CIP-51TM Microcontroller Core
1.1.1. Fully 8051 Compatible
The C8051F91x-C8051F90x family utilizes Silicon Labs' proprietary CIP-51 microcontroller core. The CIP51 is fully compatible with the MCS-51TM instruction set; standard 803x/805x assemblers and compilers can be used to develop software. The CIP-51 core offers all the peripherals included with a standard 8052.
1.1.2. Improved Throughput
The CIP-51 employs a pipelined architecture that greatly increases its instruction throughput over the standard 8051 architecture. In a standard 8051, all instructions except for MUL and DIV take 12 or 24 system clock cycles to execute with a maximum system clock of 12-to-24 MHz. By contrast, the CIP-51 core executes 70% of its instructions in one or two system clock cycles, with only four instructions taking more than four system clock cycles. The CIP-51 has a total of 109 instructions. The table below shows the total number of instructions that require each execution time. Clocks to Execute Number of Instructions 1 26 2 50 2/3 5 3 14 3/4 7 4 3 4/5 1 5 2 8 1
With the CIP-51's maximum system clock at 25 MHz, it has a peak throughput of 25 MIPS.
1.1.3. Additional Features
The C8051F91x-C8051F90x SoC family includes several key enhancements to the CIP-51 core and peripherals to improve performance and ease of use in end applications. The extended interrupt handler provides multiple interrupt sources into the CIP-51 allowing numerous analog and digital peripherals to interrupt the controller. An interrupt driven system requires less intervention by the MCU, giving it more effective throughput. The extra interrupt sources are very useful when building multi-tasking, real-time systems. Eight reset sources are available: power-on reset circuitry (POR), an on-chip VDD monitor (forces reset when power supply voltage drops below safe levels), a Watchdog Timer, a Missing Clock Detector, SmaRTClock oscillator fail or alarm, a voltage level detection from Comparator0, a forced software reset, an external reset pin, and an illegal Flash access protection circuit. Each reset source except for the POR, Reset Input Pin, or Flash error may be disabled by the user in software. The WDT may be permanently disabled in software after a power-on reset during MCU initialization. The internal oscillator factory calibrated to 24.5 MHz and is accurate to 2% over the full temperature and supply range. The internal oscillator period can also be adjusted by user firmware. An additional 20 MHz low power oscillator is also available which facilitates low-power operation. An external oscillator drive circuit is included, allowing an external crystal, ceramic resonator, capacitor, RC, or CMOS clock source to generate the system clock. If desired, the system clock source may be switched on-the-fly between both internal and external oscillator circuits. An external oscillator can also be extremely useful in low power applications, allowing the MCU to run from a slow (power saving) source, while periodically switching to the fast (up to 25 MHz) internal oscillator as needed.
20
Rev. 1.0
C8051F91x-C8051F90x
1.2. Port Input/Output
Digital and analog resources are available through 16 I/O pins. Port pins are organized as three byte-wide ports. Port pins P0.0-P1.6 can be defined as digital or analog I/O. Digital I/O pins can be assigned to one of the internal digital resources or used as general purpose I/O (GPIO). Analog I/O pins are used by the internal analog resources. P2.7 can be used as GPIO and is shared with the C2 Interface Data signal (C2D). See Section "27. C2 Interface" on page 312 for more details. The designer has complete control over which digital and analog functions are assigned to individual Port pins, limited only by the number of physical I/O pins. This resource assignment flexibility is achieved through the use of a Priority Crossbar Decoder. See Section "21.3. Priority Crossbar Decoder" on page 209 for more information on the Crossbar. All Port I/Os are 5 V tolerant when used as digital inputs or open-drain outputs. For Port I/Os configured as push-pull outputs, current is sourced from the VDD/DC+ supply. Port I/Os used for analog functions can operate up to the VDD/DC+ supply voltage. See Section "21.1. Port I/O Modes of Operation" on page 206 for more information on Port I/O operating modes and the electrical specifications chapter for detailed electrical specifications.
XBR0, XBR1, XBR2, PnSKIP Registers Port Match P0MASK, P0MAT P1MASK, P1MAT
Priority Decoder
2 4 2 SMBus CP0 CP1 Outputs SYSCLK PCA Lowest Priority 7 2 8 P0 (Port Latches) 1 (P0.0-P0.7) 7 P1 (P1.0-P1.6) 1 P2 (P2.7) To Analog Peripherals (ADC0, CP0, and CP1 inputs, VREF, IREF0, AGND) P2 I/O Cell 4
External Interrupts EX0 and EX1 PnMDOUT, PnMDIN Registers
Highest Priority
UART SPI0 SPI1
(Internal Digital Signals)
P0.0
Digital Crossbar
8
P0 I/O Cells P0.7 P1.0 P1 I/O Cells P1.6
7
T0, T1
P2.7
Figure 1.5. Port I/O Functional Block Diagram
Rev. 1.0
21
C8051F91x-C8051F90x
1.3. Serial Ports
The C8051F91x-C8051F90x Family includes an SMBus/I2C interface, a full-duplex UART with enhanced baud rate configuration, and two Enhanced SPI interfaces. Each of the serial buses is fully implemented in hardware and makes extensive use of the CIP-51's interrupts, thus requiring very little CPU intervention.
1.4.
Programmable Counter Array
An on-chip Programmable Counter/Timer Array (PCA) is included in addition to the four 16-bit general purpose counter/timers. The PCA consists of a dedicated 16-bit counter/timer time base with six programmable capture/compare modules. The PCA clock is derived from one of six sources: the system clock divided by 12, the system clock divided by 4, Timer 0 overflows, an External Clock Input (ECI), the system clock, or the external oscillator clock source divided by 8. `F912 and `F902 devices also support a SmaRTClock divided by 8 clock source. Each capture/compare module can be configured to operate in a variety of modes: edge-triggered capture, software timer, high-speed output, pulse width modulator (8, 9, 10, 11, or 16-bit), or frequency output. Additionally, Capture/Compare Module 5 offers watchdog timer (WDT) capabilities. Following a system reset, Module 5 is configured and enabled in WDT mode. The PCA Capture/Compare Module I/O and External Clock Input may be routed to Port I/O via the Digital Crossbar.
SYSCLK/12 SYSCLK/4 Timer 0 Overflow ECI SYSCLK External Clock/8 SmaRTClock/8* *Only available on `F912 and `F902 devices. PCA CLOCK MUX 16-Bit Counter/Timer
Capture/Compare Module 0
Capture/Compare Module 1
Capture/Compare Module 2
Capture/Compare Module 3
Capture/Compare Module 4
Capture/Compare Module 5 / WDT
CEX0
CEX1
CEX2
CEX3
CEX4
CEX5
ECI
Crossbar
Port I/O
Figure 1.6. PCA Block Diagram
22
Rev. 1.0
C8051F91x-C8051F90x
1.5. SAR ADC with 16-bit Auto-Averaging Accumulator and Autonomous Low Power Burst Mode
C8051F91x-C8051F90x devices have a 300 ksps, 10-bit or 75 ksps 12-bit successive-approximationregister (SAR) ADC with integrated track-and-hold and programmable window detector. ADC0 also has an autonomous low power Burst Mode which can automatically enable ADC0, capture and accumulate samples, then place ADC0 in a low power shutdown mode without CPU intervention. It also has a 16-bit accumulator that can automatically average the ADC results, providing an effective 11, 12, or 13 bit ADC result without any additional CPU intervention. The ADC can sample the voltage at any of the GPIO pins (with the exception of P2.7) and has an on-chip attenuator that allows it to measure voltages up to twice the voltage reference. Additional ADC inputs include an on-chip temperature sensor, the VDD/DC+ supply voltage, the VBAT supply voltage, and the internal digital supply voltage.
ADC0CN
BURSTEN AD0BUSY AD0WINT AD0CM2 AD0CM1 AD0CM0 000 001 010 011 100 AD0INT AD0EN VDD
ADC0TK
Burst Mode Logic
Start Conversion
AD0BUSY (W) Timer 0 Overflow Timer 2 Overflow Timer 3 Overflow CNVSTR Input
ADC0PWR
From AMUX0
AIN+
SYSCLK
REF
ADC0H
ADC
ADC0L
10/12-Bit SAR
16-Bit Accumulator
AD0WINT Window Compare Logic
AMP0GN
AD0SC4
AD0SC3
AD0SC2
AD0SC1
AD0SC0
AD08BE
AD0TM
32
ADC0LTH
ADC0LTL
ADC0CF
ADC0GTH ADC0GTL
Figure 1.7. ADC0 Functional Block Diagram
Rev. 1.0
23
C8051F91x-C8051F90x
ADC0MX
AD0MX4 AD0MX3 AD0MX2 AD0MX1 AM0MX0
P0.0
Programmable Attenuator AIN+
P1.6
Temp Sensor
AMUX
ADC0
VBAT Digital Supply VDD/DC+
Gain = 0. 5 or 1
Figure 1.8. ADC0 Multiplexer Block Diagram
1.6.
Programmable Current Reference (IREF0)
C8051F91x-C8051F90x devices include an on-chip programmable current reference (source or sink) with two output current settings: low power mode and high current mode. The maximum current output in low power mode is 63 A (1 A steps) and the maximum current output in high current mode is 504 A (8 A steps).
1.7.
Comparators
C8051F91x-C8051F90x devices include two on-chip programmable voltage comparators: Comparator 0 (CPT0) which is shown in Figure 1.9; Comparator 1 (CPT1) which is shown in Figure 1.10. The two comparators operate identically but may differ in their ability to be used as reset or wake-up sources. See Section "18. Reset Sources" on page 171 and the Section "14. Power Management" on page 143 for details on reset sources and low power mode wake-up sources, respectively. The Comparator offers programmable response time and hysteresis, an analog input multiplexer, and two outputs that are optionally available at the Port pins: a synchronous "latched" output (CP0, CP1), or an asynchronous "raw" output (CP0A, CP1A). The asynchronous CP0A signal is available even when the system clock is not active. This allows the Comparator to operate and generate an output when the device is in some low power modes. The comparator inputs may be connected to Port I/O pins or to other internal signals. Port pins may also be used to directly sense capacitive touch switches. See Application Note AN338 for details on Capacitive Touch Switch sensing.
24
Rev. 1.0
C8051F91x-C8051F90x
CP0EN CP0OUT CP0RIF CP0FIF CP0HYP1 CP0HYP0 CP0HYN1 CP0HYN0 Analog Input Multiplexer CP0MD0 CP0MD1 CP0RIE CP0FIE Px.x CP0 Rising-edge CP0 Falling-edge
CPT0CN
VDD
CP0 Interrupt
CPT0MD
CP0 + Px.x
Interrupt Logic
+
D
SET
CP0
Q D
SET
Q
Px.x GND
CLR
Q
CLR
Q
Crossbar
(SYNCHRONIZER)
CP0 -
(ASYNCHRONOUS)
CP0A
Px.x
Reset Decision Tree
Figure 1.9. Comparator 0 Functional Block Diagram
CP1EN
CPT0CN
CP1OUT CP1RIF CP1FIF CP1HYP1 CP1HYP0 CP1HYN1 CP1HYN0
VDD
CP1 Interrupt
CPT0MD
CP1MD0 CP1MD1 CP1RIE CP1FIE CP1 Rising-edge CP1 Falling-edge
Analog Input Multiplexer Px.x
CP1 + Px.x
Interrupt Logic
+
D
SET
CP1
Q D
SET
Q
Px.x GND
CLR
Q
CLR
Q
Crossbar
(SYNCHRONIZER)
CP1 -
(ASYNCHRONOUS)
CP1A
Px.x
Reset Decision Tree
Figure 1.10. Comparator 1 Functional Block Diagram
Rev. 1.0
25
C8051F91x-C8051F90x
2. Ordering Information
Table 2.1. Product Selection Guide
Programmable Current Reference SmaRTClock Real Time Clock
Programmable Counter Array
Lead-free (RoHS Compliant)
C8051F9xx Plus Features*
Internal Voltage Reference
Ordering Part Number
Analog Comparators
Temperature Sensor
10-bit 300ksps ADC
Flash Memory (kB)
Digital Port I/Os
Timers (16-bit)
Enhanced SPI
MIPS (Peak)
RAM (bytes)
SMBus/I2C
C8051F912-GM C8051F912-GU C8051F912-GD C8051F911-GM C8051F911-GU C8051F911-GD C8051F902-GM C8051F902-GU C8051F902-GD C8051F901-GM C8051F901-GU C8051F901-GD
25 16 25 16 25 16 25 16 25 16 25 16 25 8 25 8 25 8 25 8 25 8 25 8
768 768 768 768 768 768 768 768 768 768 768 768

1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1
2 2 2 2 2 2 2 2 2 2 2 2
4 4 4 4 4 4 4 4 4 4 4 4
16 16 16 16 16 16 16 16 16 16 16 16
2 2 2 2 2 2 2 2 2 2 2 2

QFN-24 QSOP-24 Tested Die QFN-24 QSOP-24 Tested Die QFN-24 QSOP-24 Tested Die QFN-24 QSOP-24 Tested Die
*The 'F9xx Plus features are a set of enhancements that allow greater power efficiency and increased functionality. They include 12-bit ADC mode, PWM Enhanced IREF, ultra-low power SmaRTClock LFO, VBAT input voltage from 0.9 to 3.6 V, and VBAT battery low indicator. The 'F9xx Plus features are described in detail in "AN431: F93x-F90x Software Porting Guide."
26
Rev. 1.0
Package
UART
C8051F91x-C8051F90x
3. Pinout and Package Definitions
Table 3.1. Pin Definitions for the C8051F91x-C8051F90x
Pin Numbers Name `F912-GM `F902-GM `F911-GM `F901-GM 5 `F912-GU `F902-GU `F911-GU `F901-GU 8 Type Description
VBAT
P In
Battery Supply Voltage. C8051F911/01 devices: Must be 0.9 to 1.8 V in single-cell battery mode and 1.8 to 3.6 V in dual-cell battery mode. C8051F912/02 devices: Must be 0.9 to 3.6 V in single-cell battery mode and 1.8 to 3.6 V in dual-cell battery mode.
VDD /
3
6
P In
Power Supply Voltage. Must be 1.8 to 3.6 V. This supply voltage is not required in low power sleep mode. This voltage must always be > VBAT. Positive output of the dc-dc converter. In single-cell battery mode, a 1uF ceramic capacitor is required between DC+ and DC-. This pin can supply power to external devices when operating in singlecell battery mode.
DC+
P Out
DC- /
1
4
P In
DC-DC converter return current path. In single-cell battery mode, this pin is typically not connected to ground. In dual-cell battery mode, this pin must be connected directly to ground. Required Ground. DC-DC Enable Pin. In single-cell battery mode, this pin must be connected to VBAT through a 0.68 H inductor. In dual-cell battery mode, this pin must be connected directly to ground. Device Reset. Open-drain output of internal POR or VDD monitor. An external source can initiate a system reset by driving this pin low for at least 15 s. A 1 k to 5 k pullup to VDD is recommended. See Section "18. Reset Sources" on page 171 Section for a complete description. Clock signal for the C2 Debug Interface. Port 2.7. This pin can only be used as GPIO. The Crossbar cannot route signals to this pin and it cannot be configured as an analog input. See Port I/O Section for a complete description. Bi-directional data signal for the C2 Debug Interface.
GND GND DCEN 2 4 5 7
G G P In
G RST/ 6 9 D I/O
C2CK P2.7/ 7 10
D I/O D I/O
C2D
D I/O
*Note: Available only on the C8051F912/02.
Rev. 1.0
27
C8051F91x-C8051F90x
Table 3.1. Pin Definitions for the C8051F91x-C8051F90x (Continued)
Pin Numbers Name `F912-GM `F902-GM `F911-GM `F901-GM 9 8 24 `F912-GU `F902-GU `F911-GU `F901-GU 12 11 3 Type Description
XTAL3 XTAL4 P0.0
A In A Out
SmaRTClock Oscillator Crystal Input. See Section 20 for a complete description. SmaRTClock Oscillator Crystal Output. See Section 20 for a complete description.
VREF
D I/O or Port 0.0. See Port I/O Section for a complete description. A In External VREF Input. A In Internal VREF Output. External VREF decoupling capacitors are A Out recommended. See Section "5.9. Voltage and Ground Reference Options" on page 83. D I/O or Port 0.1. See Port I/O Section for a complete description. A In Optional Analog Ground. See Section "5.9. Voltage and Ground G Reference Options" on page 83. D I/O or Port 0.2. See Port I/O Section for a complete description. A In External Clock Input. This pin is the external oscillator return for a A In crystal or resonator. See Section "19. Clocking Sources" on page 179. Buffered SmaRTClock oscillator output.
P0.1
23
2
AGND P0.2 22 1
XTAL1
RTCOUT* P0.3 21 24
D I/O or Port 0.3. See Section "21. Port Input/Output" on page 205 for a A In complete description. A Out D In A In External Clock Output. This pin is the excitation driver for an external crystal or resonator. External Clock Input. This pin is the external clock input in external CMOS clock mode. External Clock Input. This pin is the external clock input in capacitor or RC oscillator configurations. See Section "19. Clocking Sources" on page 179 for complete details. Wake-up request signal to wake up external devices (e.g. an external DC-DC converter).
XTAL2
WAKEOUT*
P0.4
20
23
D I/O or Port 0.4. See Section "21. Port Input/Output" on page 205 for a A In complete description. D Out UART TX Pin. See Section "21. Port Input/Output" on page 205.
TX P0.5 19 22
D I/O or Port 0.5. See Section "21. Port Input/Output" on page 205 for a complete description. A In D In UART RX Pin. See Section "21. Port Input/Output" on page 205.
RX
*Note: Available only on the C8051F912/02.
28
Rev. 1.0
C8051F91x-C8051F90x
Table 3.1. Pin Definitions for the C8051F91x-C8051F90x (Continued)
Pin Numbers Name `F912-GM `F902-GM `F911-GM `F901-GM 18 `F912-GU `F902-GU `F911-GU `F901-GU 21 Type Description
P0.6
D I/O or Port 0.6. See Section "21. Port Input/Output" on page 205 for a complete description. A In D In External Convert Start Input for ADC0. See Section "5.7. ADC0 Analog Multiplexer" on page 78 for a complete description.
CNVSTR P0.7 IREF0 P1.0 16 19 17 20
D I/O or Port 0.7. See Section "21. Port Input/Output" on page 205 for a complete description. A In A Out IREF0 Output. See IREF Section for complete description. D I/O or Port 1.0. See Section "21. Port Input/Output" on page 205 for a A In complete description. May also be used as SCK for SPI1.
P1.1
15
18
D I/O or Port 1.1. See Section "21. Port Input/Output" on page 205 for a A In complete description. May also be used as MISO for SPI1. D I/O or Port 1.2. See Section "21. Port Input/Output" on page 205 for a A In complete description. May also be used as MOSI for SPI1. D I/O or Port 1.3. See Section "21. Port Input/Output" on page 205 for a A In complete description. May also be used as NSS for SPI1. D I/O or Port 1.4. See Section "21. Port Input/Output" on page 205 for a A In complete description.
P1.2
14
17
P1.3
13
16
P1.4
12
15
P1.5
11
14
D I/O or Port 1.5. See Section "21. Port Input/Output" on page 205 for a A In complete description.
P1.6
10
13
D I/O or Port 1.6. See Section "21. Port Input/Output" on page 205 for a A In complete description.
*Note: Available only on the C8051F912/02.
Rev. 1.0
29
C8051F91x-C8051F90x
P0.3/XTAL2/WAKEOUT*
P0.2/XTAL1/RTCOUT*
P0.1/AGND
P0.0/VREF
24
23
22
21
20
GND/DC- GND VDD/DC+ DCEN VBAT RST/C2CK
1 2 3 4 5 6
19
P0.5/RX
P0.4/TX
18
P0.6/CNVSTR P0.7/IREF0 P1.0 P1.1 P1.2 P1.3
C8051F912/02-GM C8051F911/01-GM Top View
GND (Optional Connection)
17 16 15 14 13
10
11 P1.5
P2.7/C2D
XTAL4
XTAL3
P1.6
*Note: Signal only available on 'F912 and 'F902 devices.
Figure 3.1. QFN-24 Pinout Diagram (Top View)
30
Rev. 1.0
P1.4
12
7
8
9
C8051F91x-C8051F90x
P0.2/XTAL1/RTCOUT* P0.1/AGND P0.0/VREF GND/DCGND VDD/DC+ DCEN VBAT RST/C2CK P2.7/C2D XTAL4 XTAL3
1 2 3 4 5 6 7 8 9 10 11 12
24 23 22 21 20 19 18 17 16 15 14 13
P0.3/XTAL2/WAKEOUT* P0.4/TX P0.5/RX P0.6/CNVSTR P0.7/IREF0 P1.0 P1.1 P1.2 P1.3 P1.4 P1.5 P1.6
*Note: Signal only available on 'F912 and 'F902 devices.
Figure 3.2. QSOP-24 Pinout Diagram F912 (Top View)
C8051F912/02 - GU C8051F911/01 - GU
Rev. 1.0
31
C8051F91x-C8051F90x
Figure 3.3. QFN-24 Package Drawing Table 3.2. QFN-24 Package Dimensions
Dimension A A1 b D D2 e E E2 2.55 2.55 Min 0.70 0.00 0.18 Typ 0.75 0.02 0.25 4.00 BSC 2.70 0.50 BSC 4.00 BSC 2.70 2.80 2.80 Max 0.80 0.05 0.30 Dimension L L1 aaa bbb ddd eee Z Y Min 0.30 0.00 -- -- -- -- -- -- Typ 0.40 -- -- -- -- -- 0.24 0.18 Max 0.50 0.15 0.15 0.10 0.05 0.08 -- --
Notes: 1. All dimensions shown are in millimeters (mm) unless otherwise noted. 2. Dimensioning and Tolerancing per ANSI Y14.5M-1994. 3. This drawing conforms to the JEDEC Solid State Outline MO-220, variation WGGD except for custom features D2, E2, Z, Y, and L which are toleranced per supplier designation. 4. Recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small Body Components.
32
Rev. 1.0
C8051F91x-C8051F90x
Figure 3.4. Typical QFN-24 Landing Diagram Table 3.3. PCB Land Pattern
Dimension C1 C2 E Min 3.90 3.90 0.50 BSC Max 4.00 4.00 Dimension X1 X2 Y1 Y Notes: General 1. All dimensions shown are in millimeters (mm) unless otherwise noted. 2. This Land Pattern Design is based on the IPC-7351 guidelines. Solder Mask Design 1. All metal pads are to be non-solder mask defined (NSMD). Clearance between the solder mask and the metal pad is to be 60 m minimum, all the way around the pad. Stencil Design 1. A stainless steel, laser-cut and electro-polished stencil with trapezoidal walls should be used to assure good solder paste release. 2. The stencil thickness should be 0.125 mm (5 mils). 3. The ratio of stencil aperture to land pad size should be 1:1 for all perimeter pads. 4. A 2 x 2 array of 1.0 x 1.0 mm square openings on 1.30 mm pitch should be used for the center ground pad. Card Assembly 1. A No-Clean, Type-3 solder paste is recommended. 2. The recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small Body Components. Min 0.20 2.70 0.65 2.70 Max 0.30 2.80 0.75 2.80
Rev. 1.0
33
C8051F91x-C8051F90x
Figure 3.5. QSOP-24 Package Diagram Table 3.4. QSOP-24 Package Dimensions
Dimension A A1 b c D E E1 Min -- 0.10 0.20 0.10 Nom -- -- -- -- 8.65 BSC 6.00 BSC 3.90 BSC Max 1.75 0.25 0.30 0.25 Dimension e L aaa bbb ccc ddd 0.40 0 Min Nom 0.635 BSC -- -- 0.20 0.18 0.10 0.10 1.27 8 Max
Notes: 1. All dimensions shown are in millimeters (mm) unless otherwise noted. 2. Dimensioning and Tolerancing per ANSI Y14.5M-1994. 3. This drawing conforms to JEDEC outline MO-137, variation AE. 4. Recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small Body Components.
34
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C8051F91x-C8051F90x
Figure 3.6. QSOP-24 Landing Diagram Table 3.5. PCB Land Pattern
Dimension C E X Y MIN 5.20 0.635 BSC 0.30 1.50 0.40 1.60 MAX 5.30
Notes: General 1. All dimensions shown are in millimeters (mm) unless otherwise noted. 2. This land pattern is based on the IPC-7351 guidelines. Solder Mask Design 1. All metal pads are to be non-solder mask defined (NMSD). Clearance between the solder mask and the metal pad is to be 60 m minimum, all the way around the pad. Stencil Design 1. A stainless steel, laser-cut and electro-polished stencil with trapezoidal walls should be used to assure good solder paste release. 2. The stencil thickness should be 0.125 mm (5 mils). 3. The ratio of stencil aperture to land pad size should be 1:1 for all perimeter pads. Card Assembly 1. A No-Clean, Type 3 solder paste is recommended. 2. The recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small Body Components.
Rev. 1.0
35
C8051F91x-C8051F90x
4. Electrical Characteristics
Throughout the Electrical Characteristics chapter, "VDD" refers to the VDD/DC+ Supply Voltage. Blue indicates a feature only available on `F912 and `F902 devices.
4.1.
Absolute Maximum Specifications
Table 4.1. Absolute Maximum Ratings
Parameter Ambient temperature under bias Storage Temperature Voltage on any Port I/O Pin or RST with respect to GND Voltage on VBAT with respect to GND Voltage on VDD/DC+ with respect to GND Maximum total current through VBAT, DCEN, VDD/DC+ or GND Maximum current through RST or any Port pin Maximum total current through all Port pins DC-DC Converter Output Power VDD > 2.2 V VDD < 2.2 V One-Cell Mode (F912/02 One-Cell Mode (F911/01) Two-Cell Mode Conditions Min -55 -65 -0.3 -0.3 -0.3 -0.3 -0.3 -0.3 -- -- -- -- Typ -- -- -- -- -- -- -- -- -- -- -- -- Max 125 150 5.8 VDD + 3.6 4.0 2.0 4.0 4.0 500 100 200 110 Units C C V V
V mA mA mA mW
Note: Stresses above those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress rating only and functional operation of the devices at those or any other conditions above those indicated in the operation listings of this specification is not implied. Exposure to maximum rating conditions for extended periods may affect device reliability.
36
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C8051F91x-C8051F90x
4.2. Electrical Characteristics
Table 4.2. Global Electrical Characteristics
-40 to +85 C, 25 MHz system clock unless otherwise specified. See "AN358: Optimizing Low Power Operation of the `F9xx" for details on how to achieve the supply current specifications listed in this table. Parameter Battery Supply Voltage (VBAT) Conditions One-Cell Mode (F912/02) One-Cell Mode (F911/01) Two-Cell Mode One-Cell Mode Two-Cell Mode VDD (not in Sleep Mode) VBAT (in Sleep Mode) Min 0.9 0.9 1.8 1.8 1.8 -- -- 0 18 18 -40 Typ 1.2 1.2 2.4 1.9 2.4 1.4 0.3 -- -- -- -- Max 3.6 1.8 3.6 3.6 3.6 -- 0.5 25 -- -- +85 Units V
Supply Voltage (VDD/DC+) Minimum RAM Data Retention Voltage1 SYSCLK (System Clock)2 TSYSH (SYSCLK High Time) TSYSL (SYSCLK Low Time) Specified Operating Temperature Range
V V MHz ns ns C
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37
C8051F91x-C8051F90x
Table 4.2. Global Electrical Characteristics (Continued)
-40 to +85 C, 25 MHz system clock unless otherwise specified. See "AN358: Optimizing Low Power Operation of the `F9xx" for details on how to achieve the supply current specifications listed in this table. Parameter IDD 3, 4, 5, 6 Conditions VDD = 1.8-3.6 V, F = 24.5 MHz (includes precision oscillator current) VDD = 1.8-3.6 V, F = 20 MHz (includes low power oscillator current) VDD = 1.8 V, F = 1 MHz VDD = 3.6 V, F = 1 MHz (includes external oscillator/GPIO current) VDD = 1.8-3.6 V, F = 32.768 kHz (includes SmaRTClock oscillator current) IDD Frequency Sensitivity3, 5, 6 VDD = 1.8-3.6 V, T = 25 C, F < 14 MHz (Flash oneshot active, see Section 13.6) VDD = 1.8-3.6 V, T = 25 C, F > 14 MHz (Flash oneshot bypassed, see Section 13.6) IDD4, 6, 7 VDD = 1.8-3.6 V, F = 24.5 MHz (includes precision oscillator current) VDD = 1.8-3.6 V, F = 20 MHz (includes low power oscillator current) VDD = 1.8 V, F = 1 MHz VDD = 3.6 V, F = 1 MHz (includes external oscillator/GPIO current) VDD = 1.8-3.6 V, F = 32.768 kHz (includes SmaRTClock oscillator current) IDD Frequency Sensitivity1,6,7 VDD = 1.8-3.6 V, T = 25 C Min -- -- -- -- -- -- -- Typ 4.0 3.4 265 305 84 191 102 Max 5.0 -- -- -- -- -- -- Units mA mA A A A A/MHz A/MHz
Digital Supply Current--CPU Active (Normal Mode, fetching instructions from Flash)
Digital Supply Current--CPU Inactive (Idle Mode, not fetching instructions from Flash) -- -- -- -- -- -- 2.1 1.6 160 185 82 79 3.0 -- -- -- -- -- mA mA A A A A/MHz
38
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Table 4.2. Global Electrical Characteristics (Continued)
-40 to +85 C, 25 MHz system clock unless otherwise specified. See "AN358: Optimizing Low Power Operation of the `F9xx" for details on how to achieve the supply current specifications listed in this table. Parameter Digital Supply Current6 (Suspend Mode) Conditions VDD = 1.8-3.6 V, two-cell mode Min -- -- -- -- -- -- -- Typ 77 0.60 0.75 0.85 1.30 1.60 1.90 Max -- -- -- -- -- -- -- Units A A
Digital Supply Current--Suspend and Sleep Mode
Digital Supply Current 1.8 V, T = 25 C (Sleep Mode, SmaRTClock run- 3.0 V, T = 25 C ning, 32.768 kHz crystal) 3.6 V, T = 25 C 1.8 V, T = 85 C 3.0 V, T = 85 C 3.6 V, T = 85 C (includes SmaRTClock oscillator and VBAT Supply Monitor) 1.8 V, T = 25 C Digital Supply Current8 (Sleep Mode, SmaRTClock run- (includes SmaRTClock oscillator and VBAT Supply Monitor) ning, internal LFO) Digital Supply Current (Sleep Mode) 1.8 V, T = 25 C 3.0 V, T = 25 C 3.6 V, T = 25 C 1.8 V, T = 85 C 3.0 V, T = 85 C 3.6 V, T = 85 C (includes VBAT supply monitor) 1.8 V, T = 25 C
--
0.3
--
A
-- -- -- -- -- -- --
0.05 0.08 0.12 0.75 0.90 1.20 0.01
-- -- -- -- -- -- --
A
Digital Supply Current (Sleep Mode, VBAT Supply Monitor Disabled)9
A
Rev. 1.0
39
C8051F91x-C8051F90x
Table 4.2. Global Electrical Characteristics (Continued)
-40 to +85 C, 25 MHz system clock unless otherwise specified. See "AN358: Optimizing Low Power Operation of the `F9xx" for details on how to achieve the supply current specifications listed in this table. Parameter Conditions Min Typ Max Units
Notes: 1. Based on device characterization data; Not production tested. 2. SYSCLK must be at least 32 kHz to enable debugging. 3. Digital Supply Current depends upon the particular code being executed. The values in this table are obtained with the CPU executing an "sjmp $" loop, which is the compiled form of a while(1) loop in C. One iteration requires 3 CPU clock cycles, and the Flash memory is read on each cycle. The supply current will vary slightly based on the physical location of the sjmp instruction and the number of Flash address lines that toggle as a result. In the worst case, current can increase by up to 30% if the sjmp loop straddles a 64-byte Flash address boundary (e.g., 0x007F to 0x0080). Real-world code with larger loops and longer linear sequences will have few transitions across the 64-byte address boundaries. 4. Includes oscillator and regulator supply current. 5. IDD can be estimated for frequencies <14 MHz by simply multiplying the frequency of interest by the frequency sensitivity number for that range, then adding an offset of 90 A. When using these numbers to estimate IDD for >14 MHz, the estimate should be the current at 25 MHz minus the difference in current indicated by the frequency sensitivity number. For example: VDD = 3.0 V; F = 20 MHz, IDD = 4 mA - (25 MHz - 20 MHz) x 0.102 mA/MHz = 3.5 mA assuming the same oscillator setting. 6. The supply current specifications in Table 4.2 are for two cell mode. The VBAT current in one-cell mode can be estimated using the following equation: Supply Voltage Supply Current (two-cell mode) VBAT Current (one-cell mode) = ---------------------------------------------------------------------------------------------------------------------------------DC-DC Converter Efficiency VBAT Voltage The VBAT Voltage is the voltage at the VBAT pin, typically 0.9 to 1.8 V. The Supply Current (two-cell mode) is the data sheet specification for supply current. The Supply Voltage is the voltage at the VDD/DC+ pin, typically 1.8 to 3.3 V (default = 1.9 V). The DC-DC Converter Efficiency can be estimated using Figure 4.3-Figure 4.5. 7. Idle IDD can be estimated by taking the current at 25 MHz minus the difference in current indicated by the frequency sensitivity number. For example: VDD = 3.0 V; F = 5 MHz, Idle IDD = 2.1 mA - (25 MHz - 5 MHz) x 0.079 mA/MHz = 0.52 mA. 8. Internal LFO only available on `F912 and `F902 devices. 9. Ability to disable VBAT supply monitor only available on `F912 and `F902 devices.
40
Rev. 1.0
C8051F91x-C8051F90x
4200 4100 4000 3900 3800 3700 3600 3500 3400 3300 3200 3100 3000 2900 2800 2700 2600 2500 Supply Current (uA) 2400 2300 2200 2100 2000 1900 1800 1700 1600 1500 1400 1300 1200 1100 1000 900 800 700 600 500 400 300 200 100 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Frequency (MHz)
F < 14 MHz Oneshot Enabled
F > 14 MHz Oneshot Bypassed
< 160 uA/MHz
185 uA/MHz
200 uA/MHz
215 uA/MHz
300 uA/MHz
Figure 4.1. Active Mode Current (External CMOS Clock)
Rev. 1.0
41
C8051F91x-C8051F90x
4200 4100 4000 3900 3800 3700 3600 3500 3400 3300 3200 3100 3000 2900 2800 2700 2600 2500 Supply Current (uA) 2400 2300 2200 2100 2000 1900 1800 1700 1600 1500 1400 1300 1200 1100 1000 900 800 700 600 500 400 300 200 100 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Frequency (MHz)
Figure 4.2. Idle Mode Current (External CMOS Clock)
42
Rev. 1.0
C8051F91x-C8051F90x

6:6(/
6:6(/
Efficiency (%)

9%$7 9%$7 9%$7 9%$7 9%$7 9%$7 9%$7
9 9 9 9 9 9 9
X+ ,QGXFWRU SDFNDJH (65 2KPV 9'''& 9 0LQLPXP 3XOVH :LGWK QV 3XOVH 6NLSSLQJ 'LVDEOHG 1RWH (IILFLHQF\ DW KLJK FXUUHQWV PD\ EH LPSURYHG E\ FKRRVLQJ DQ LQGXFWRU ZLWK D ORZHU (65

Load Current (mA)
Figure 4.3. Typical DC-DC Converter Efficiency (High Current, VDD/DC+ = 2 V)
Rev. 1.0
43
C8051F91x-C8051F90x
6:6(/ 6:6(/

9%$7 9%$7 9%$7 9%$7 9%$7 9%$7 9%$7
9 9 9 9 9 9 9
Efficiency (%)

X+ ,QGXFWRU SDFNDJH (65 2KPV 9'''& 9 0LQLPXP 3XOVH :LGWK QV 3XOVH 6NLSSLQJ 'LVDEOHG 1RWH (IILFLHQF\ DW KLJK FXUUHQWV PD\ EH LPSURYHG E\ FKRRVLQJ DQ LQGXFWRU ZLWK D ORZHU (65

Load current (mA)
Figure 4.4. Typical DC-DC Converter Efficiency (High Current, VDD/DC+ = 3 V)
44
Rev. 1.0
C8051F91x-C8051F90x

9%$7
Efficiency (%)
9 9 9 9 9 9 9
9%$7 9%$7 9%$7 9%$7 9%$7 9%$7
X+ ,QGXFWRU SDFNDJH (65 2KPV 6:6(/ 9'''& 9 0LQLPXP 3XOVH :LGWK
QV

Load current (mA)
Figure 4.5. Typical DC-DC Converter Efficiency (Low Current, VDD/DC+ = 2 V)
Rev. 1.0
45
C8051F91x-C8051F90x
9%$7 &XUUHQW X$ 9%$7 9
X+ ,QGXFWRU SDFNDJH (65 2KPV 6:6(/ 9'''& 9 /RDG &XUUHQW X$
0LQ 3XOVH :LGWK QV 0LQ 3XOVH :LGWK QV 0LQ 3XOVH :LGWK QV 0LQ 3XOVH :LGWK QV
Figure 4.6. Typical One-Cell Suspend Mode Current
46
Rev. 1.0
C8051F91x-C8051F90x
Table 4.3. Port I/O DC Electrical Characteristics
VDD = 1.8 to 3.6 V, -40 to +85 C unless otherwise specified.
Parameters
Conditions IOH = -3 mA, Port I/O push-pull IOH = -10 A, Port I/O push-pull IOH = -10 mA, Port I/O push-pull Low Drive Strength, PnDRV.n = 0 IOH = -1 mA, Port I/O push-pull IOH = -10 A, Port I/O push-pull IOH = -3 mA, Port I/O push-pull
Min VDD - 0.7 VDD - 0.1
Typ -- -- See Chart
Max -- --
Units
Output High Voltage High Drive Strength, PnDRV.n = 1
V VDD - 0.7 VDD - 0.1 -- -- -- See Chart -- -- --
Output Low Voltage High Drive Strength, PnDRV.n = 1 IOL = 8.5 mA IOL = 10 A IOL = 25 mA Low Drive Strength, PnDRV.n = 0 IOL = 1.4 mA IOL = 10 A IOL = 4 mA Input High Voltage Input Low Voltage VDD = 2.0 to 3.6 V VDD = 0.9 to 2.0 V VDD = 2.0 to 3.6 V VDD = 0.9 to 2.0 V Input Leakage Current Weak Pullup Off Weak Pullup On, VIN = 0 V, VDD = 1.8 V Weak Pullup On, Vin = 0 V, VDD = 3.6 V -- -- -- VDD - 0.6 0.7 x VDD -- -- -- -- -- -- -- See Chart -- -- -- -- -- 4 20 0.6 0.1 -- -- -- 0.6 0.3 x VDD 1 -- 35 A V V V V -- -- -- -- -- See Chart 0.6 0.1 -- V
Rev. 1.0
47
C8051F91x-C8051F90x
Typical VOH (High Drive Mode) 3.6 3.3 3 2.7 Voltage 2.4 2.1 1.8 1.5 1.2 0.9 0 5 10 15 20 25 30 35 40 45 50 Load Current (mA) Typical VOH (Low Drive Mode) 3.6 3.3 3 2.7 Voltage 2.4 2.1 1.8 1.5 1.2 0.9 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Load Current (mA) VDD = 3.6V VDD = 3.0V VDD = 2.4V VDD = 1.8V VDD = 3.6V VDD = 3.0V VDD = 2.4V VDD = 1.8V
Figure 4.7. Typical VOH Curves, 1.8-3.6 V
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C8051F91x-C8051F90x
Typical VOH (High Drive Mode) 1.8 1.7 1.6 1.5 1.4 1.3 Voltage 1.2 1.1 1 0.9 0.8 0.7 0.6 0.5 0 1 2 3 4 5 6 7 8 9 10 11 12 Load Current (mA) Typical VOH (Low Drive Mode) 1.8 1.7 1.6 1.5 1.4 1.3 Voltage 1.2 1.1 1 0.9 0.8 0.7 0.6 0.5 0 1 2 Load Current (mA) 3 VDD = 0.9V VDD = 1.5V VDD = 1.2V VDD = 1.8V VDD = 0.9V VDD = 1.5V VDD = 1.2V VDD = 1.8V
Figure 4.8. Typical VOH Curves, 0.9-1.8 V
Rev. 1.0
49
C8051F91x-C8051F90x
Typical VOL (High Drive Mode) 1.8 VDD = 3.6V 1.5 VDD = 3.0V 1.2 Voltage VDD = 2.4V VDD = 1.8V
0.9
0.6
0.3
0 -80 -70 -60 -50 -40 -30 -20 -10 0 Load Current (mA) Typical VOL (Low Drive Mode) 1.8 VDD = 3.6V 1.5 VDD = 3.0V 1.2 Voltage VDD = 2.4V VDD = 1.8V
0.9
0.6
0.3
0 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 Load Current (mA)
Figure 4.9. Typical VOL Curves, 1.8-3.6 V
50
Rev. 1.0
C8051F91x-C8051F90x
Typical VOL (High Drive Mode) 0.5 VDD = 1.8V 0.4 VDD = 1.5V VDD = 1.2V VDD = 0.9V 0.2
Voltage
0.3
0.1
0 -5 -4 -3 -2 -1 0 Load Current (mA) Typical VOL (Low Drive Mode) 0.5
0.4
Voltage
0.3 VDD = 1.8V 0.2 VDD = 1.5V VDD = 1.2V 0.1 VDD = 0.9V 0 -3 -2 Load Current (mA) -1 0
Figure 4.10. Typical VOL Curves, 0.9-1.8 V
Rev. 1.0
51
C8051F91x-C8051F90x
Table 4.4. Reset Electrical Characteristics
VDD = 1.8 to 3.6 V, -40 to +85 C unless otherwise specified.
Parameter RST Output Low Voltage RST Input High Voltage
Conditions IOL = 1.4 mA, VDD = 2.0 to 3.6 V VDD = 0.9 to 2.0 V
Min -- VDD - 0.6 0.7 x VDD -- -- -- -- 1.8 1.7 -- -- 0.9 0.7 -- 100
Typ -- -- -- -- -- 4 20 1.85 1.75 -- 0.75 1.0 0.8 0.95 525
Max 0.6 -- -- 0.6 0.3 x VDD -- 35 1.9 1.8 3 -- 1.1 0.9 -- 1000
Units V V V V V A V
RST Input Low Voltage
VDD = 2.0 to 3.6 V VDD = 0.9 to 2.0 V
RST Input Pullup Current VDD/DC+ Monitor Threshold (VRST) VBAT Ramp Time for Power On VBAT Monitor Threshold (VPOR)
RST = 0.0 V, VDD = 1.8 V RST = 0.0 V, VDD = 3.6 V Early Warning Reset Trigger (all power modes except Sleep) VBAT Ramp from 0-0.9 V Initial Power-On (VBAT Rising) Early Warning Brownout Condition (VBAT Falling) Recovery from Brownout (VBAT Rising) Time from last system clock rising edge to reset initiation System clock frequency which triggers a missing clock detector timeout Delay between release of any reset source and code execution at location 0x0000
ms
V
Missing Clock Detector Timeout Minimum System Clock w/ Missing Clock Detector Enabled Reset Time Delay Minimum RST Low Time to Generate a System Reset VDD Monitor Turn-on Time VDD Monitor Supply Current
s
--
2
10
kHz
--
10
--
s
15 -- --
-- 300 10
-- -- --
s ns A
*Note: Blue indicates a feature only available on `F912 and `F902 devices.
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Table 4.5. Power Management Electrical Specifications
VDD = 1.8 to 3.6 V, -40 to +85 C unless otherwise specified.
Parameter Idle Mode Wake-up Time Suspend Mode Wake-up Time
Conditions
Min 2
Typ -- 400 400 2 10
Max 3 -- -- -- --
Units SYSCLKs ns ns s s
Low power oscillator Precision oscillator
-- -- -- --
Sleep Mode Wake-up Time
Two-cell mode One-cell mode
Table 4.6. Flash Electrical Characteristics
VDD = 1.8 to 3.6 V, -40 to +85 C unless otherwise specified.
Parameter Flash Size
Conditions C8051F912/1 C8051F902/1
Min 16384* 8192 512 1k 28 57
Typ -- -- -- 90 k 32 64
Max -- -- 512 -- 36 71
Units bytes bytes bytes Erase/Write Cycles ms s
Scratchpad Size Endurance Erase Cycle Time Write Cycle Time
*Note: On 16 kB devices, 1024 bytes at addresses 0x3C00 to 0x3FFF are reserved.
Table 4.7. Internal Precision Oscillator Electrical Characteristics
VDD = 1.8 to 3.6 V; TA = -40 to +85 C unless otherwise specified; Using factory-calibrated settings.
Parameter Oscillator Frequency Oscillator Supply Current (from VDD)
Conditions -40 to +85 C, VDD = 1.8-3.6 V 25 C; includes bias current of 90-100 A
Min 24 --
Typ 24.5 300*
Max 25 --
Units MHz A
*Note: Does not include clock divider or clock tree supply current.
Table 4.8. Internal Low-Power Oscillator Electrical Characteristics
VDD = 1.8 to 3.6 V; TA = -40 to +85 C unless otherwise specified; Using factory-calibrated settings.
Parameter Oscillator Frequency Oscillator Supply Current (from VDD)
Conditions -40 to +85 C, VDD = 1.8-3.6 V 25 C No separate bias current required.
Min 18 --
Typ 20 100*
Max 22 --
Units MHz A
*Note: Does not include clock divider or clock tree supply current.
Rev. 1.0
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C8051F91x-C8051F90x
Table 4.9. SmaRTClock Characteristics
VDD = 1.8 to 3.6 V; TA = -40 to +85 C unless otherwise specified; Using factory-calibrated settings.
Parameter Conditions Min Oscillator Frequency (LFO) 13.1 Note: Blue indicates a feature only available on `F912 and `F902 devices.
Typ 16.4
Max 19.7
Units kHz
Table 4.10. ADC0 Electrical Characteristics VDD = 1.8 to 3.6V V, VREF = 1.65 V (REFSL[1:0] = 11), -40 to +85 C unless otherwise specified.
Conditions Min DC Accuracy 12-bit mode 12 Resolution 10-bit mode 10 12-bit mode 2 -- Integral Nonlinearity 10-bit mode -- Differential Nonlinearity 12-bit mode2 -- (Guaranteed Monotonic) 10-bit mode -- 12-bit mode -- Offset Error 10-bit mode -- 12-bit mode3 -- Full Scale Error 10-bit mode -- Dynamic performance (10 kHz sine-wave single-ended input, 1 dB below Full Scale, maximum sampling rate) 12-bit mode 62 Signal-to-Noise Plus Distortion4 10-bit mode 54 12-bit mode -- Signal-to-Distortion4 10-bit mode -- 12-bit mode -- Spurious-Free Dynamic Range4 10-bit mode -- Conversion Rate Normal Mode -- SAR Conversion Clock Low Power Mode -- Conversion Time in SAR Clocks Track/Hold Acquisition Time Throughput Rate 10-bit Mode 8-bit Mode Initial Acquisition Subsequent Acquisitions (DC input, burst mode) 12-bit mode 10-bit mode 13 11 1.5 1.1 -- -- Parameter Typ Max Units bits 1 0.5 0.8 0.5 <1 <1 1 1 1.5 1 1 1 2 2 4 2.5 LSB LSB LSB LSB
65 58 76 73 82 75 -- -- -- -- --
-- -- -- -- -- -- 8.33 4.4 -- -- --
dB dB dB
MHz
clocks us
-- --
75 300
ksps
Notes: 1. Blue indicates a feature only available on `F912 and `F902 devices. 2. INL and DNL specifications for 12-bit mode do not include the first or last four ADC codes. 3. The maximum code in 12-bit mode is 0xFFFC. The Full Scale Error is referenced from the maximum code. 4. Performance in 8-bit mode is similar to 10-bit mode.
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Table 4.10. ADC0 Electrical Characteristics (Continued) VDD = 1.8 to 3.6V V, VREF = 1.65 V (REFSL[1:0] = 11), -40 to +85 C unless otherwise specified.
Parameter Analog Inputs ADC Input Voltage Range Absolute Pin Voltage with respect to GND Sampling Capacitance (C8051F912/11/02/01) Input Multiplexer Impedance Power Specifications Power Supply Current (VDD supplied to ADC0) Power Supply Rejection Conditions Single Ended (AIN+ - GND) Single Ended 1x Gain 0.5x Gain Min 0 0 -- -- Conversion Mode (300 ksps) Tracking Mode (0 ksps) Internal High Speed VREF External VREF -- -- -- -- Typ -- -- 28 26 5 720 680 67 74 Max VREF VDD -- -- -- -- -- -- Units V V pF k A dB
Notes: 1. Blue indicates a feature only available on `F912 and `F902 devices. 2. INL and DNL specifications for 12-bit mode do not include the first or last four ADC codes. 3. The maximum code in 12-bit mode is 0xFFFC. The Full Scale Error is referenced from the maximum code. 4. Performance in 8-bit mode is similar to 10-bit mode.
Table 4.11. Temperature Sensor Electrical Characteristics
VDD = 1.8 to 3.6V V, -40 to +85 C unless otherwise specified. Parameter Linearity Slope Slope Error Offset Offset Error
1 1
Conditions
Min -- -- --
Typ 1 3.40 40 1025 18 -- 35
Max -- -- -- -- -- 3.0 6.5 --
Units C mV/C V/C mV mV s A
Temp = 25 C Temp = 25 C Initial Voltage=0 V Initial Voltage=3.6 V
-- -- -- --
Temperature Sensor Settling Time2 Supply Current
Notes: 1. Represents one standard deviation from the mean. 2. The temperature sensor settling time, resulting from an ADC mux change or enabling of the temperature sensor, varies with the voltage of the previously sampled channel and can be up to 6 s if the previously sampled channel voltage was greater than 3 V. To minimize the temperature sensor settling time, the ADC mux can be momentarily set to ground before being set to the temperature sensor output. This ensures that the temperature sensor output will settle in 3 s or less.
Rev. 1.0
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C8051F91x-C8051F90x
Table 4.12. Voltage Reference Electrical Characteristics
VDD = 1.8 to 3.6 V, -40 to +85 C unless otherwise specified. Parameter Conditions Internal High Speed Reference (REFSL[1:0] = 11) Output Voltage VREF Turn-on Time Supply Current Normal Power Mode Low Power Mode -40 to +85 C, VDD = 1.8-3.6 V Load = 0 to 200 A to AGND 4.7 F tantalum, 0.1 F ceramic bypass, settling to 0.5 LSB 0.1 F ceramic bypass, settling to 0.5 LSB no bypass cap, settling to 0.5 LSB -40 to +85 C, VDD = 1.8-3.6 V Min 1.60 -- -- -- 1.645 -- -- -- -- -- -- 0 Sample Rate = 300 ksps; VREF = 3.0 V -- Typ 1.65 -- 260 140 1.680 10 400 15 300 25 15 -- 5.25 Max 1.70 1.5 -- -- 1.715 -- -- -- -- -- -- VDD -- Units V s A
Internal Precision Reference (REFSL[1:0] = 00, REFOE = 1) Output Voltage VREF Short-Circuit Current Load Regulation VREF Turn-on Time 1 VREF Turn-on Time 2 VREF Turn-on Time 3 Supply Current External Reference (REFSL[1:0] = 00, REFOE = 0) Input Voltage Range Input Current V A V mA V/A ms s s A
Note: Blue indicates a feature only available on `F912 and `F902 devices.
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Table 4.13. IREF0 Electrical Characteristics
VDD = 1.8 to 3.6 V, -40 to +85 C, unless otherwise specified.
Parameter Static Performance Resolution1 Low Power Mode, Source High Current Mode, Source Low Power Mode, Sink High Current Mode, Sink 0 0 0.3 0.8 -- -- -- Low Power Mode, Source Full Scale Error2 High Current Mode, Source Low Power Mode, Sink High Current Mode, Sink Absolute Current Error Dynamic Performance Output Settling Time to 1/2 LSB Startup Time Power Consumption Net Power Supply Current (VDD supplied to IREF0 minus any output source current) Low Power Mode, Source IREF0DAT = 000001 IREF0DAT = 111111 High Current Mode, Source IREF0DAT = 000001 IREF0DAT = 111111 Low Power Mode, Sink IREF0DAT = 000001 IREF0DAT = 111111 High Current Mode, Sink IREF0DAT = 000001 IREF0DAT = 111111 -- -- 12 81 -- -- A A -- -- 1 11 -- -- A A -- -- 10 10 -- -- A A -- -- 10 10 -- -- A A -- -- 300 1 -- -- ns s Low Power Mode Sourcing 20 A -- -- -- -- -- 6 -- -- -- -- <0.2 <0.2 <0.1 -- -- -- -- <1 VDD - 0.4 VDD - 0.8 VDD VDD 1.0 1.0 0.5 5 6 8 8 3 bits V Conditions Min Typ Max Units
Output Compliance Range
Integral Nonlinearity Differential Nonlinearity Offset Error
LSB LSB LSB % % % % %
Notes: 1. Refer to "PWM Enhanced Mode" on page 86 for information on how to improve IREF0 resolution. 2. Full scale is 63 A in Low Power Mode and 504 A in High Power Mode.
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Table 4.14. Comparator Electrical Characteristics
VDD = 1.8 to 3.6 V, -40 to +85 C unless otherwise noted.
Parameter Response Time: Mode 0, VDD = 2.4 V, VCM* = 1.2 V Response Time: Mode 1, VDD = 2.4 V, VCM* = 1.2 V Response Time: Mode 2, VDD = 2.4 V, VCM* = 1.2 V Response Time: Mode 3, VDD = 2.4 V, VCM* = 1.2 V Common-Mode Rejection Ratio Inverting or Non-Inverting Input Voltage Range Input Capacitance Input Bias Current Input Offset Voltage Power Supply Power Supply Rejection
Conditions CP0+ - CP0- = 100 mV CP0+ - CP0- = -100 mV CP0+ - CP0- = 100 mV CP0+ - CP0- = -100 mV CP0+ - CP0- = 100 mV CP0+ - CP0- = -100 mV CP0+ - CP0- = 100 mV CP0+ - CP0- = -100 mV
Min -- -- -- -- -- -- -- -- -- -0.25 -- -- -7
Typ 130 200 210 410 420 1200 1750 6200 1.5 -- 12 1 --
Max -- -- -- -- -- -- -- -- 4 VDD + 0.25 -- -- +7
Units ns ns ns ns ns ns ns ns mV/V V pF nA mV
-- VDD = 3.6 V VDD = 3.0 V -- -- -- -- -- -- -- --
0.1 0.6 1.0 1.8 10 23 8.8 2.6 0.4
-- -- -- -- -- -- -- -- --
mV/V s s s s A A A A
Power-up Time VDD = 2.4 V VDD = 1.8 V Mode 0 Mode 1 Supply Current at DC Mode 2 Mode 3
*Note: Vcm is the common-mode voltage on CP0+ and CP0-.
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Table 4.14. Comparator Electrical Characteristics (Continued)
VDD = 1.8 to 3.6 V, -40 to +85 C unless otherwise noted.
Parameter Hysteresis Mode 0 Hysteresis 1 Hysteresis 2 Hysteresis 3 Hysteresis 4 Mode 1 Hysteresis 1 Hysteresis 2 Hysteresis 3 Hysteresis 4 Mode 2 Hysteresis 1 Hysteresis 2 Hysteresis 3 Hysteresis 4 Mode 3 Hysteresis 1 Hysteresis 2 Hysteresis 3 Hysteresis 4
Conditions
Min
Typ
Max
Units
(CPnHYP/N1-0 = 00) (CPnHYP/N1-0 = 01) (CPnHYP/N1-0 = 10) (CPnHYP/N1-0 = 11) (CPnHYP/N1-0 = 00) (CPnHYP/N1-0 = 01) (CPnHYP/N1-0 = 10) (CPnHYP/N1-0 = 11) (CPnHYP/N1-0 = 00) (CPnHYP/N1-0 = 01) (CPnHYP/N1-0 = 10) (CPnHYP/N1-0 = 11) (CPnHYP/N1-0 = 00) (CPnHYP/N1-0 = 01) (CPnHYP/N1-0 = 10) (CPnHYP/N1-0 = 11)
-- -- -- -- -- -- -- -- -- 2 5 12 -- -- -- --
0 8.5 17 34 0 6.5 13 26 0 5 10 20 0 4.5 9 17
-- -- -- -- -- -- -- -- 1 10 20 30 -- -- -- --
mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV
*Note: Vcm is the common-mode voltage on CP0+ and CP0-.
Table 4.15. VREG0 Electrical Characteristics
VDD = 1.8 to 3.6 V, -40 to +85 C unless otherwise specified.
Parameter Input Voltage Range Bias Current
Conditions
Min 1.8
Typ -- 20
Max 3.6 --
Units V A
Normal, idle, suspend, or stop mode
--
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Table 4.16. DC-DC Converter (DC0) Electrical Characteristics
VBAT = 0.9 to 1.8 V, -40 to +85 C unless otherwise specified.
Parameter Input Voltage Range Input Inductor Value Input Inductor Current Rating Inductor DC Resistance Input Capacitor Value Output Voltage Range
Conditions C8051F912/02 C8051F911/01
Min 0.9 0.9 500 250 --
Typ -- -- 680 -- -- 4.7 1.0 1.80 1.90 2.00 2.10 2.40 2.70 3.00 3.30 0.3 1 -- -- -- -- -- -- -- -- -- 80 100 70 85 2.4 -- 1.0
Max 3.6 1.8 900 -- 0.5 -- -- 1.87 1.97 2.07 2.17 2.50 2.80 3.10 3.42 -- -- 36 34 32 30 27 24 21 19 65 -- -- -- -- 3.2 1 2.0
Units V nH mA F
Source Impedance < 2 Target Output = 1.8 V Target Output = 1.9 V Target Output = 2.0 V Target Output = 2.1 V Target Output = 2.4 V Target Output = 2.7 V Target Output = 3.0 V Target Output = 3.3 V Target Output = 2.0 V, 1 to 30 mA Target Output = 3.0 V, 1 to 20 mA Target Output = 1.8 V Target Output = 1.9 V Target Output = 2.0 V Target Output = 2.1 V Target Output = 2.4 V Target Output = 2.7 V Target Output = 3.0 V Target Output = 3.3 V
-- -- 1.73 1.83 1.93 2.03 2.30 2.60 2.90 3.18 -- -- -- -- -- -- -- -- -- -- --
V
Output Load Regulation Output Current (based on output power spec)
%
mA
Output Power Bias Current (Normal Current Mode) Bias Current (Low Power Mode) Clocking Frequency Maximum DC Load Current During Startup Capacitance Connected to Output from VBAT supply from VDD/DC+ supply from VBAT supply from VDD/DC+ supply
mW A
-- -- -- -- 1.6 -- 0.8
MHz mA F
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5. SAR ADC with 16-bit Auto-Averaging Accumulator and Autonomous Low Power Burst Mode
The ADC0 on C8051F91x-C8051F90x devices is a 300 ksps, 10-bit or 75 ksps, 12-bit (`F912/02 only) successive-approximation-register (SAR) ADC with integrated track-and-hold and programmable window detector. ADC0 also has an autonomous low power Burst Mode which can automatically enable ADC0, capture and accumulate samples, then place ADC0 in a low power shutdown mode without CPU intervention. It also has a 16-bit accumulator that can automatically oversample and average the ADC results. See Section 5.4 for more details on using the ADC in 12-bit mode. The ADC is fully configurable under software control via Special Function Registers. The ADC0 operates in Single-ended mode and may be configured to measure various different signals using the analog multiplexer described in "5.7. ADC0 Analog Multiplexer" on page 78. The voltage reference for the ADC is selected as described in "5.9. Voltage and Ground Reference Options" on page 83.
ADC0CN
BURSTEN AD0BUSY AD0WINT AD0CM2 AD0CM1 AD0CM0 000 001 010 011 100 AD0INT AD0EN VDD
ADC0TK
Burst Mode Logic
Start Conversion
AD0BUSY (W ) Timer 0 Overflow Timer 2 Overflow Timer 3 Overflow CNVSTR Input
ADC0PWR
From AMUX0
AIN+
SYSCLK
REF
ADC0H
ADC
ADC0L
10/12-Bit SAR
16-Bit Accumulator
AD0WINT W indow Compare Logic
AMP0GN
AD0SC4
AD0SC3
AD0SC2
AD0SC1
AD0SC0
AD08BE
AD0TM
32
ADC0LTH
ADC0LTL
ADC0CF
ADC0GTH ADC0GTL
Figure 5.1. ADC0 Functional Block Diagram
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5.1. Output Code Formatting
The registers ADC0H and ADC0L contain the high and low bytes of the output conversion code from the ADC at the completion of each conversion. Data can be right-justified or left-justified, depending on the setting of the AD0SJST[2:0]. When the repeat count is set to 1, conversion codes are represented as 10bit unsigned integers. Inputs are measured from 0 to VREF x 1023/1024. Example codes are shown below for both right-justified and left-justified data. Unused bits in the ADC0H and ADC0L registers are set to 0. Input Voltage VREF x 1023/1024 VREF x 512/1024 VREF x 256/1024 0 Right-Justified ADC0H:ADC0L (AD0SJST = 000) 0x03FF 0x0200 0x0100 0x0000 Left-Justified ADC0H:ADC0L (AD0SJST = 100) 0xFFC0 0x8000 0x4000 0x0000
When the repeat count is greater than 1, the output conversion code represents the accumulated result of the conversions performed and is updated after the last conversion in the series is finished. Sets of 4, 8, 16, 32, or 64 consecutive samples can be accumulated and represented in unsigned integer format. The repeat count can be selected using the AD0RPT bits in the ADC0AC register. When a repeat count higher than 1, the ADC output must be right-justified (AD0SJST = 0xx); unused bits in the ADC0H and ADC0L registers are set to 0. The example below shows the right-justified result for various input voltages and repeat counts. Notice that accumulating 2n samples is equivalent to left-shifting by n bit positions when all samples returned from the ADC have the same value. Input Voltage VREF x 1023/1024 VREF x 512/1024 VREF x 511/1024 0 Repeat Count = 4 0x0FFC 0x0800 0x07FC 0x0000 Repeat Count = 16 0x3FF0 0x2000 0x1FF0 0x0000 Repeat Count = 64 0xFFC0 0x8000 0x7FC0 0x0000
The AD0SJST bits can be used to format the contents of the 16-bit accumulator. The accumulated result can be shifted right by 1, 2, or 3 bit positions. Based on the principles of oversampling and averaging, the effective ADC resolution increases by 1 bit each time the oversampling rate is increased by a factor of 4. The example below shows how to increase the effective ADC resolution by 1, 2, and 3 bits to obtain an effective ADC resolution of 11-bit, 12-bit, or 13-bit respectively without CPU intervention. Input Voltage Repeat Count = 4 Shift Right = 1 11-Bit Result 0x07F7 0x0400 0x03FE 0x0000 Repeat Count = 16 Shift Right = 2 12-Bit Result 0x0FFC 0x0800 0x04FC 0x0000 Repeat Count = 64 Shift Right = 3 13-Bit Result 0x1FF8 0x1000 0x0FF8 0x0000
VREF x 1023/1024 VREF x 512/1024 VREF x 511/1024 0
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5.2. Modes of Operation
ADC0 has a maximum conversion speed of 300 ksps in 10-bit mode. The ADC0 conversion clock (SARCLK) is a divided version of the system clock when Burst Mode is disabled (BURSTEN = 0), or a divided version of the low power oscillator when Burst Mode is enabled (BURSEN = 1). The clock divide value is determined by the AD0SC bits in the ADC0CF register.
5.2.1. Starting a Conversion
A conversion can be initiated in one of five ways, depending on the programmed states of the ADC0 Start of Conversion Mode bits (AD0CM2-0) in register ADC0CN. Conversions may be initiated by one of the following: 1. 2. 3. 4. 5. Writing a 1 to the AD0BUSY bit of register ADC0CN A Timer 0 overflow (i.e., timed continuous conversions) A Timer 2 overflow A Timer 3 overflow A rising edge on the CNVSTR input signal (pin P0.6)
Writing a 1 to AD0BUSY provides software control of ADC0 whereby conversions are performed "ondemand". During conversion, the AD0BUSY bit is set to logic 1 and reset to logic 0 when the conversion is complete. The falling edge of AD0BUSY triggers an interrupt (when enabled) and sets the ADC0 interrupt flag (AD0INT). When polling for ADC conversion completions, the ADC0 interrupt flag (AD0INT) should be used. Converted data is available in the ADC0 data registers, ADC0H:ADC0L, when bit AD0INT is logic 1. When Timer 2 or Timer 3 overflows are used as the conversion source, Low Byte overflows are used if Timer 2/3 is in 8-bit mode; High byte overflows are used if Timer 2/3 is in 16-bit mode. See "25. Timers" on page 270 for timer configuration. Important Note About Using CNVSTR: The CNVSTR input pin also functions as Port pin P0.6. When the CNVSTR input is used as the ADC0 conversion source, Port pin P0.6 should be skipped by the Digital Crossbar. To configure the Crossbar to skip P0.6, set to 1 Bit 6 in register P0SKIP. See "21. Port Input/Output" on page 205 for details on Port I/O configuration. Important Note: When operating the device in one-cell mode, there is an option available to automatically synchronize the start of conversion with the quietest portion of the dc-dc converter switching cycle. Activating this option may help to reduce interference from internal or external power supply noise generated by the dc-dc converter. Asserting this bit will hold off the start of an ADC conversion initiated by any of the methods described above until the ADC receives a synchronizing signal from the dc-dc converter. The delay in initiation of the conversion can be as much as one cycle of the dc-dc converter clock, which is 625 ns at the minimum dc-dc clock frequency of 1.6 MHz. The synchronization feature also causes the dc-dc converter clock to be used as the ADC0 conversion clock. The maximum conversion rate will be limited to approximately 170 ksps at the maximum dc-dc converter clock rate of 3.2 MHz. In this mode, the ADC0 SAR Conversion Clock Divider must be set to 1 by setting AD0SC[4:0] = 00000b in SFR register ADC0CF. To provide additional flexibility in minimizing noise, the ADC0 conversion clock provided by the dc-dc converter can be inverted by setting the AD0CKINV bit in the DC0CF register. For additional information on the synchronization feature, see the description of the SYNC bit in "SFR Definition 16.1. DC0CN: DC-DC Converter Control" on page 167 and the description of the AD0CKINV bit in "SFR Definition 16.2. DC0CF: DC-DC Converter Configuration" on page 168. This bit must be set to 0 in two-cell mode for the ADC to operate.
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5.2.2. Tracking Modes
Each ADC0 conversion must be preceded by a minimum tracking time in order for the converted result to be accurate. The minimum tracking time is given in Table 4.10. The AD0TM bit in register ADC0CN controls the ADC0 track-and-hold mode. In its default state when Burst Mode is disabled, the ADC0 input is continuously tracked, except when a conversion is in progress. When the AD0TM bit is logic 1, ADC0 operates in low-power track-and-hold mode. In this mode, each conversion is preceded by a tracking period of 3 SAR clocks (after the start-of-conversion signal). When the CNVSTR signal is used to initiate conversions in low-power tracking mode, ADC0 tracks only when CNVSTR is low; conversion begins on the rising edge of CNVSTR (see Figure 5.2). Tracking can also be disabled (shutdown) when the device is in low power standby or sleep modes. Low-power track-and-hold mode is also useful when AMUX settings are frequently changed, due to the settling time requirements described in "5.2.4. Settling Time Requirements" on page 66.
A. ADC0 Timing for External Trigger Source
CNVSTR (AD0CM[2:0]=100)
1 2 3 4 5 6 7 8 9 10 11 12 13 14
SAR Clocks Low Power or Convert Low Power Mode
AD0TM=1
Track
Convert
AD0TM=0
Track or Convert
Convert
Track
Write '1' to AD0BUSY, Timer 0, Timer 2, Timer 1, Timer 3 Overflow (AD0CM[2:0]=000, 001,010 011, 101) SAR Clocks AD0TM=1
B. ADC0 Timing for Internal Trigger Source
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Low Power Track or Convert
Convert
Low Power Mode
1 2 3 4 5 6 7 8 9 10 11 12 13 14
SAR Clocks AD0TM=0 Track or Convert Convert Track
Figure 5.2. 10-Bit ADC Track and Conversion Example Timing (BURSTEN = 0)
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5.2.3. Burst Mode
Burst Mode is a power saving feature that allows ADC0 to remain in a low power state between conversions. When Burst Mode is enabled, ADC0 wakes from a low power state, accumulates 1, 4, 8, 16, 32, or 64 using an internal Burst Mode clock (approximately 20 MHz), then re-enters a low power state. Since the Burst Mode clock is independent of the system clock, ADC0 can perform multiple conversions then enter a low power state within a single system clock cycle, even if the system clock is slow (e.g. 32.768 kHz), or suspended. Burst Mode is enabled by setting BURSTEN to logic 1. When in Burst Mode, AD0EN controls the ADC0 idle power state (i.e. the state ADC0 enters when not tracking or performing conversions). If AD0EN is set to logic 0, ADC0 is powered down after each burst. If AD0EN is set to logic 1, ADC0 remains enabled after each burst. On each convert start signal, ADC0 is awakened from its Idle Power State. If ADC0 is powered down, it will automatically power up and wait the programmable Power-Up Time controlled by the AD0PWR bits. Otherwise, ADC0 will start tracking and converting immediately. Figure 5.3 shows an example of Burst Mode Operation with a slow system clock and a repeat count of 4. When Burst Mode is enabled, a single convert start will initiate a number of conversions equal to the repeat count. When Burst Mode is disabled, a convert start is required to initiate each conversion. In both modes, the ADC0 End of Conversion Interrupt Flag (AD0INT) will be set after "repeat count" conversions have been accumulated. Similarly, the Window Comparator will not compare the result to the greater-than and less-than registers until "repeat count" conversions have been accumulated. In Burst Mode, tracking is determined by the settings in AD0PWR and AD0TK. The default settings for these registers will work in most applications without modification; however, settling time requirements may need adjustment in some applications. Refer to "5.2.4. Settling Time Requirements" on page 66 for more details.
Notes:
* *
Setting AD0TM to 1 will insert an additional 3 SAR clocks of tracking before each conversion, regardless of the settings of AD0PWR and AD0TK. When using Burst Mode, care must be taken to issue a convert start signal no faster than once every four SYSCLK periods. This includes external convert start signals.
S yste m C lo ck
C o n ve rt S ta rt
AD0TM = 1 AD0EN = 0 AD0TM = 0 AD0EN = 0
P o w e re d D ow n P o w e re d D ow n
P o w e r-U p a n d T ra ck P o w e r-U p a n d T ra ck AD0PW R
T 3
C
T
T 3
C
T
T 3
C
T
T 3
C
P o w e re d D ow n
P o w e r-U p a n d T ra ck P o w e r-U p a n d T ra ck
T C ..
C
T
C
T
C
T
C
P o w e re d D own
T C ..
AD0TK
T = T ra ckin g se t b y A D 0 T K T 3 = T ra ckin g se t b y A D 0 T M (3 S A R clo cks) C = C o n ve rtin g
Figure 5.3. Burst Mode Tracking Example with Repeat Count Set to 4
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5.2.4. Settling Time Requirements
A minimum amount of tracking time is required before each conversion can be performed, to allow the sampling capacitor voltage to settle. This tracking time is determined by the AMUX0 resistance, the ADC0 sampling capacitance, any external source resistance, and the accuracy required for the conversion. Note that in low-power tracking mode, three SAR clocks are used for tracking at the start of every conversion. For many applications, these three SAR clocks will meet the minimum tracking time requirements, and higher values for the external source impedance will increase the required tracking time. Figure 5.4 shows the equivalent ADC0 input circuit. The required ADC0 settling time for a given settling accuracy (SA) may be approximated by Equation 5.1. When measuring the Temperature Sensor output or VDD with respect to GND, RTOTAL reduces to RMUX. See Table 4.10 for ADC0 minimum settling time requirements as well as the mux impedance and sampling capacitor values.
2t = ln ------ R TOTAL C SAMPLE SA
Equation 5.1. ADC0 Settling Time Requirements
Where: SA is the settling accuracy, given as a fraction of an LSB (for example, 0.25 to settle within 1/4 LSB) t is the required settling time in seconds RTOTAL is the sum of the AMUX0 resistance and any external source resistance. n is the ADC resolution in bits (10).
MUX Select
n
P0.x R MUX C SAMPLE RCInput= R MUX * C SAMPLE
Note: The value of CSAMPLE depends on the PGA Gain. See Table 4.10 for details.
Figure 5.4. ADC0 Equivalent Input Circuits
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5.2.5. Gain Setting
The ADC has gain settings of 1x and 0.5x. In 1x mode, the full scale reading of the ADC is determined directly by VREF. In 0.5x mode, the full-scale reading of the ADC occurs when the input voltage is VREF x 2. The 0.5x gain setting can be useful to obtain a higher input Voltage range when using a small VREF voltage, or to measure input voltages that are between VREF and VDD. Gain settings for the ADC are controlled by the AMP0GN bit in register ADC0CF.
5.3.
8-Bit Mode
Setting the ADC08BE bit in register ADC0CF to 1 will put the ADC in 8-bit mode.In 8-bit mode, only the 8 MSBs of data are converted, allowing the conversion to be completed in two fewer SAR clock cycles than a 10-bit conversion. This can result in an overall lower power consumption since the system can spend more time in a low power mode. The two LSBs of a conversion are always 00 in this mode, and the ADC0L register will always read back 0x00.
5.4.
12-Bit Mode (C8051F912/02 Only)
C8051F912/02 devices have an enhanced SAR converter that provides 12-bit resolution while retaining the 10- and 8-bit operating modes of the other devices in the family. When configured for 12-bit conversions, the ADC performs four 10-bit conversions using four different reference voltages and combines the results into a single 12-bit value. Unlike simple averaging techniques, this method provides true 12-bit resolution of AC or DC input signals without depending on noise to provide dithering. The converter also employs a hardware Dynamic Element Matching algorithm that reconfigures the largest elements of the internal DAC for each of the four 10-bit conversions to cancel the any matching errors, enabling the converter to achieve 12-bit linearity performance to go along with its 12-bit resolution. For best performance, the Low Power Oscillator should be selected as the system clock source while taking 12-bit ADC measurements. The 12-bit mode is enabled by setting the AD012BE bit (ADC0AC.7) to logic 1 and configuring Burst Mode for four conversions as described in Section 5.2.3. The conversion can be initiated using any of the methods described in Section 5.2.1, and the 12-bit result will appear in the ADC0H and ADC0L registers. Since the 12-bit result is formed from a combination of four 10-bit results, the maximum output value is 4 x (1023) = 4092, rather than the max value of (2^12 - 1) = 4095 that is produced by a traditional 12-bit converter. To further increase resolution, the burst mode repeat value may be configured to any multiple of four conversions. For example, if a repeat value of 16 is selected, the ADC0 output will be a 14-bit number (sum of four 12-bit numbers) with 13 effective bits of resolution.
5.5.
Low Power Mode (C8051F912/902 only)
The C8051F912/02 SAR converter provides a low power mode that allows a significant reduction in operating current when operating at low SAR clock frequencies. Low power mode is enabled by setting the AD0LPM bit (ADC0PWR.7) to 1. In general, low power mode is recommended when operating with SAR conversion clock frequency at 4 MHz or less. See the Electrical Characteristics chapter for details on power consumption and the maximum clock frequencies allowed in each mode. Setting the Low Power Mode bit reduces the bias currents in both the SAR converter and in the High-Speed Voltage Reference. describes the various modes of the ADC.
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Table 5.1. Representative Conversion Times and Energy Consumption for the SAR ADC with 1.65 V High-Speed VREF
Normal Power Mode 8 bit 10 bit 8.17 MHz (24.5 / 3) 12 bit 8 bit Low Power Mode 10 bit 12 bit
Highest nominal SAR clock frequency Total number of conversion clocks required Total tracking time (min) Total time for one conversion
8.17 MHz (24.5 / 3)
6.67 MHz (20.0 / 3) 52 (13*4) 4.8 us (1.5+3*1.1)
4.08 MHz (24.5 / 6)
4.08 MHz (24.5 / 6)
4.00 MHz (20.0 / 5) 52 (13*4) 4.8 us (1.5+3*1.1)
11 1.5 us
13 1.5 us
11 1.5 us
13 1.5 us
2.85 us
3.09 us 323 ksps 8.9 nJ
12.6 us
4.19 us
4.68 us
17.8 us
ADC Throughput Energy per conversion
351 ksps 8.2 nJ
79 ksps 36.5 nJ
238 ksps 6.5 nJ
214 ksps 7.3 nJ
56 ksps 27.7 nJ
Note: This table assumes that the 24.5 MHz precision oscillator is used for 8- and 10-bit modes, and the 20 MHz low power oscillator is used for 12-bit mode. The values in the table assume that the oscillators run at their nominal frequencies. The maximum SAR clock values given in Table 4.10 allow for maximum oscillation frequencies of 25.0 MHz and 22 MHz for the precision and low-power oscillators, respectively, when using the given SAR clock divider values. Energy calculations are for the ADC subsystem only and do not include CPU current. Modes in BLUE are only available on 'F912 and 'F902 devices.
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SFR Definition 5.1. ADC0CN: ADC0 Control
Bit Name Type Reset 7 AD0EN R/W 0 6 BURSTEN R/W 0 5 AD0INT R/W 0 4 3 2 1 ADC0CM R/W 0 0 0 0
AD0BUSY AD0WINT W 0 R/W 0
SFR Page = 0x0; SFR Address = 0xE8; bit-addressable
;
Bit
7
Name
AD0EN ADC0 Enable.
Function
0: ADC0 Disabled (low-power shutdown). 1: ADC0 Enabled (active and ready for data conversions).
6
BURSTEN
ADC0 Burst Mode Enable. 0: ADC0 Burst Mode Disabled. 1: ADC0 Burst Mode Enabled.
5
AD0INT
ADC0 Conversion Complete Interrupt Flag. Set by hardware upon completion of a data conversion (BURSTEN=0), or a burst of conversions (BURSTEN=1). Can trigger an interrupt. Must be cleared by software.
4 3
AD0BUSY AD0WINT
ADC0 Busy. Writing 1 to this bit initiates an ADC conversion when ADC0CM[2:0] = 000. ADC0 Window Compare Interrupt Flag. Set by hardware when the contents of ADC0H:ADC0L fall within the window specified by ADC0GTH:ADC0GTL and ADC0LTH:ADC0LTL. Can trigger an interrupt. Must be cleared by software.
2:0
ADC0CM[2:0] ADC0 Start of Conversion Mode Select. Specifies the ADC0 start of conversion source. 000: ADC0 conversion initiated on write of 1 to AD0BUSY. 001: ADC0 conversion initiated on overflow of Timer 0. 010: ADC0 conversion initiated on overflow of Timer 2. 011: ADC0 conversion initiated on overflow of Timer 3. 1xx: ADC0 conversion initiated on rising edge of CNVSTR.
Note:
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SFR Definition 5.2. ADC0CF: ADC0 Configuration
Bit Name Type Reset 1 1 7 6 5 AD0SC[4:0] R/W 1 1 1 4 3 2 AD08BE R/W 0 1 AD0TM R/W 0 0 AMP0GN R/W 0
SFR Page = 0x0; SFR Address = 0xBC
Bit
7:3
Name
Function
SAR Conversion clock is derived from FCLK by the following equation, where AD0SC refers to the 5-bit value held in bits AD0SC[4:0]. SAR Conversion clock requirements are given in Table 4.10. BURSTEN = 0: FCLK is the current system clock. BURSTEN = 1: FCLK is the 20 MHz low power oscillator, independent of the system clock.
AD0SC[4:0] ADC0 SAR Conversion Clock Divider.
FCLK AD0SC = ------------------- - 1 * CLK SAR
*Round the result up. or
FCLK CLK SAR = ---------------------------AD0SC + 1
2 AD08BE ADC0 8-Bit Mode Enable. 0: ADC0 operates in 10-bit mode (normal operation). 1: ADC0 operates in 8-bit mode. 1 AD0TM ADC0 Track Mode. Selects between Normal or Delayed Tracking Modes. 0: Normal Track Mode: When ADC0 is enabled, conversion begins immediately following the start-of-conversion signal. 1: Delayed Track Mode: When ADC0 is enabled, conversion begins 3 SAR clock cycles following the start-of-conversion signal. The ADC is allowed to track during this time. 0 AMP0GN ADC0 Gain Control. 0: The on-chip PGA gain is 0.5. 1: The on-chip PGA gain is 1.
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SFR Definition 5.3. ADC0AC: ADC0 Accumulator Configuration
Bit 7 6 AD0AE W 0 0 5 4 AD0SJST R/W 0 0 0 3 2 1 AD0RPT R/W 0 0 0
Name AD012BE Type Reset R/W 0
SFR Page = 0x0; SFR Address = 0xBA
Bit
7
Name
AD012BE ADC0 12-Bit Mode Enable.
Function
Enables 12-bit Mode. Only available on `F912 and `F902 devices. 0: 12-bit Mode Disabled. 1: 12-bit Mode Enabled.
6
AD0AE
ADC0 Accumulate Enable. Enables multiple conversions to be accumulated when burst mode is disabled. 0: ADC0H:ADC0L contain the result of the latest conversion when Burst Mode is disabled. 1: ADC0H:ADC0L contain the accumulated conversion results when Burst Mode is disabled. Software must write 0x0000 to ADC0H:ADC0L to clear the accumulated result. This bit is write-only. Always reads 0b.
5:3
AD0SJST[2:0] ADC0 Accumulator Shift and Justify. Specifies the format of data read from ADC0H:ADC0L. 000: Right justified. No shifting applied. 001: Right justified. Shifted right by 1 bit. 010: Right justified. Shifted right by 2 bits. 011: Right justified. Shifted right by 3 bits. 100: Left justified. No shifting applied. All remaining bit combinations are reserved.
2:0
AD0RPT[2:0] ADC0 Repeat Count. Selects the number of conversions to perform and accumulate in Burst Mode. This bit field must be set to 000 if Burst Mode is disabled. 000: Perform and Accumulate 1 conversion. 001: Perform and Accumulate 4 conversions. 010: Perform and Accumulate 8 conversions. 011: Perform and Accumulate 16 conversions. 100: Perform and Accumulate 32 conversions. 101: Perform and Accumulate 64 conversions. All remaining bit combinations are reserved.
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SFR Definition 5.4. ADC0PWR: ADC0 Burst Mode Power-Up Time
Bit Name Type Reset 7 AD0LPM R/W 0 R 0 R 0 R 0 1 1 6 5 4 3 2 1 0
AD0PWR[3:0] R/W 1 1
SFR Page = 0xF; SFR Address = 0xBA
Bit
7
Name
AD0LPM ADC0 Low Power Mode Enable.
Function
Enables Low Power Mode Operation. Only available on `F912 and `F902 devices. 0: Low Power Mode disabled. 1: Low Power Mode enabled.
6:4 3:0
Unused
Unused. Read = 0000b; Write = Don't Care.
AD0PWR[3:0] ADC0 Burst Mode Power-Up Time. Sets the time delay required for ADC0 to power up from a low power state. For BURSTEN = 0: ADC0 power state controlled by AD0EN. For BURSTEN = 1 and AD0EN = 1: ADC0 remains enabled and does not enter a low power state after all conversions are complete. Conversions can begin immediately following the start-of-conversion signal. For BURSTEN = 1 and AD0EN = 0: ADC0 enters a low power state after all conversions are complete. Conversions can begin a programmed delay after the start-of-conversion signal. The ADC0 Burst Mode Power-Up time is programmed according to the following equation:
or
AD0PWR = Tstartup - 1 ---------------------400ns Tstartup = AD0PWR + 1 400ns
Note: Setting AD0PWR to 0x04 provides a typical tracking time of 2 us for the first sample taken after the start of conversion.
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SFR Definition 5.5. ADC0TK: ADC0 Burst Mode Track Time
Bit Name Type Reset 7 Reserved R 0 R 0 0 1 1 6 5 4 3 2 1 0
AD0TK[5:0] R/W 1 1 0
SFR Page = 0xF; SFR Address = 0xBD
Bit
7:6 6 5:0
Name
Reserved Unused Reserved. Read = 0b; Write = Must Write 0b. Unused. Read = 0b; Write = Don't Care. AD0TK[5:0] ADC0 Burst Mode Track Time.
Function
Sets the time delay between consecutive conversions performed in Burst Mode. The ADC0 Burst Mode Track time is programmed according to the following equation:
or
AD0TK = 63 - Ttrack - 1 --------------- 50ns Ttrack = 64 - AD0TK 50ns
Notes: 1. If AD0TM is set to 1, an additional 3 SAR clock cycles of Track time will be inserted prior to starting the conversion. 2. The Burst Mode Track delay is not inserted prior to the first conversion. The required tracking time for the first conversion should be met by the Burst Mode Power-Up Time.
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SFR Definition 5.6. ADC0H: ADC0 Data Word High Byte
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
ADC0[15:8] R/W 0 0 0 0
SFR Page = 0x0; SFR Address = 0xBE Bit Name Description 7:0 ADC0[15:8] ADC0 Data Word High Byte.
Read Most Significant Byte of the 16-bit ADC0 Accumulator formatted according to the settings in AD0SJST[2:0].
Write Set the most significant byte of the 16-bit ADC0 Accumulator to the value written.
Note: If Accumulator shifting is enabled, the most significant bits of the value read will be zeros. This register should not be written when the SYNC bit is set to 1.
SFR Definition 5.7. ADC0L: ADC0 Data Word Low Byte
Bit Name Type Reset 0 0 0 0 7 6 5 4 ADC0[7:0] R/W 0 0 0 0 3 2 1 0
SFR Page = 0x0; SFR Address = 0xBD; Bit Name Description 7:0 ADC0[7:0] ADC0 Data Word Low Byte.
Read Least Significant Byte of the 16-bit ADC0 Accumulator formatted according to the settings in AD0SJST[2:0].
Write Set the least significant byte of the 16-bit ADC0 Accumulator to the value written.
Note: If Accumulator shifting is enabled, the most significant bits of the value read will be the least significant bits of the accumulator high byte. This register should not be written when the SYNC bit is set to 1.
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5.6. Programmable Window Detector
The ADC Programmable Window Detector continuously compares the ADC0 output registers to userprogrammed limits, and notifies the system when a desired condition is detected. This is especially effective in an interrupt-driven system, saving code space and CPU bandwidth while delivering faster system response times. The window detector interrupt flag (AD0WINT in register ADC0CN) can also be used in polled mode. The ADC0 Greater-Than (ADC0GTH, ADC0GTL) and Less-Than (ADC0LTH, ADC0LTL) registers hold the comparison values. The window detector flag can be programmed to indicate when measured data is inside or outside of the user-programmed limits, depending on the contents of the ADC0 Less-Than and ADC0 Greater-Than registers.
SFR Definition 5.8. ADC0GTH: ADC0 Greater-Than High Byte
Bit Name Type Reset 1 1 1 1 7 6 5 4 3 2 1 0
AD0GT[15:8] R/W 1 1 1 1
SFR Page = 0x0; SFR Address = 0xC4 Bit Name 7:0 AD0GT[15:8] ADC0 Greater-Than High Byte.
Function
Most Significant Byte of the 16-bit Greater-Than window compare register.
SFR Definition 5.9. ADC0GTL: ADC0 Greater-Than Low Byte
Bit Name Type Reset 1 1 1 1 7 6 5 4 3 2 1 0
AD0GT[7:0] R/W 1 1 1 1
SFR Page = 0x0; SFR Address = 0xC3 Bit Name 7:0 AD0GT[7:0] ADC0 Greater-Than Low Byte.
Function
Least Significant Byte of the 16-bit Greater-Than window compare register.
Note: In 8-bit mode, this register should be set to 0x00.
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SFR Definition 5.10. ADC0LTH: ADC0 Less-Than High Byte
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
AD0LT[15:8] R/W 0 0 0 0
SFR Page = 0x0; SFR Address = 0xC6
Bit
7:0
Name
AD0LT[15:8] ADC0 Less-Than High Byte.
Function
Most Significant Byte of the 16-bit Less-Than window compare register.
SFR Definition 5.11. ADC0LTL: ADC0 Less-Than Low Byte
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
AD0LT[7:0] R/W 0 0 0 0
SFR Page = 0x0; SFR Address = 0xC5
Bit
7:0
Name
AD0LT[7:0] ADC0 Less-Than Low Byte.
Function
Least Significant Byte of the 16-bit Less-Than window compare register.
Note: In 8-bit mode, this register should be set to 0x00.
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5.6.1. Window Detector In Single-Ended Mode
Figure 5.5 shows two example window comparisons for right-justified data, with ADC0LTH:ADC0LTL = 0x0080 (128d) and ADC0GTH:ADC0GTL = 0x0040 (64d). The input voltage can range from 0 to VREF x (1023/1024) with respect to GND, and is represented by a 10-bit unsigned integer value. In the left example, an AD0WINT interrupt will be generated if the ADC0 conversion word (ADC0H:ADC0L) is within the range defined by ADC0GTH:ADC0GTL and ADC0LTH:ADC0LTL (if 0x0040 < ADC0H:ADC0L < 0x0080). In the right example, and AD0WINT interrupt will be generated if the ADC0 conversion word is outside of the range defined by the ADC0GT and ADC0LT registers (if ADC0H:ADC0L < 0x0040 or ADC0H:ADC0L > 0x0080). Figure 5.6 shows an example using leftjustified data with the same comparison values.
ADC0H:ADC0L Input Voltage (Px.x - GND) VREF x (1023/1024) 0x03FF AD0WINT not affected 0x0081 VREF x (128/1024) 0x0080 0x007F AD0WINT=1 VREF x (64/1024) 0x0041 0x0040 0x003F ADC0GTH:ADC0GTL VREF x (64/1024) 0x0041 0x0040 0x003F ADC0LTH:ADC0LTL VREF x (128/1024) 0x0081 0x0080 0x007F ADC0GTH:ADC0GTL AD0WINT not affected ADC0LTH:ADC0LTL Input Voltage (Px.x - GND) VREF x (1023/1024) 0x03FF ADC0H:ADC0L
AD0WINT=1
AD0WINT not affected 0 0x0000 0 0x0000
AD0WINT=1
Figure 5.5. ADC Window Compare Example: Right-Justified Single-Ended Data
ADC0H:ADC0L Input Voltage (Px.x - GND) VREF x (1023/1024) 0xFFC0 AD0WINT not affected 0x2040 VREF x (128/1024) 0x2000 0x1FC0 AD0WINT=1 0x1040 VREF x (64/1024) 0x1000 0x0FC0 ADC0GTH:ADC0GTL VREF x (64/1024) ADC0LTH:ADC0LTL VREF x (128/1024) Input Voltage (Px.x - GND) VREF x (1023/1024)
ADC0H:ADC0L
0xFFC0
AD0WINT=1
0x2040 0x2000 0x1FC0 0x1040 0x1000 0x0FC0 ADC0GTH:ADC0GTL AD0WINT not affected ADC0LTH:ADC0LTL
AD0WINT not affected 0 0x0000 0 0x0000
AD0WINT=1
Figure 5.6. ADC Window Compare Example: Left-Justified Single-Ended Data 5.6.2. ADC0 Specifications
See "4. Electrical Characteristics" on page 36 for a detailed listing of ADC0 specifications.
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5.7. ADC0 Analog Multiplexer
ADC0 on C8051F91x-C8051F90x has an analog multiplexer, referred to as AMUX0. AMUX0 selects the positive inputs to the single-ended ADC0. Any of the following may be selected as the positive input: Port I/O pins, the on-chip temperature sensor, the VBAT Power Supply, Regulated Digital Supply Voltage (Output of VREG0), VDD/DC+ Supply, or the positive input may be connected to GND. The ADC0 input channels are selected in the ADC0MX register described in SFR Definition 5.12.
ADC0MX
AD0MX4 AD0MX3 AD0MX2 AD0MX1 AM0MX0
P0.0
Programmable Attenuator AIN+
P1.6*
Temp Sensor
AMUX
ADC0
VBAT Digital Supply VDD/DC+
Gain = 0.5 or 1
Figure 5.7. ADC0 Multiplexer Block Diagram
Important Note About ADC0 Input Configuration: Port pins selected as ADC0 inputs should be configured as analog inputs, and should be skipped by the Digital Crossbar. To configure a Port pin for analog input, set to 0 the corresponding bit in register PnMDIN and disable the digital driver (PnMDOUT = 0 and Port Latch = 1). To force the Crossbar to skip a Port pin, set to 1 the corresponding bit in register PnSKIP. See Section "21. Port Input/Output" on page 205 for more Port I/O configuration details.
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SFR Definition 5.12. ADC0MX: ADC0 Input Channel Select
Bit Name Type Reset R 0 R 0 R 0 R/W 1 R/W 1 7 6 5 4 3 2 AD0MX R/W 1 R/W 1 R/W 1 1 0
SFR Page = 0x0; SFR Address = 0xBB
Bit
7:5 4:0
Name
Unused AD0MX Unused. Read = 000b; Write = Don't Care.
Function
AMUX0 Positive Input Selection. Selects the positive input channel for ADC0. 00000: 00001: 00010: 00011: 00100: 00101: 00110: 00111: 01000: 01001: 01010: 01011: 01100: 01101: 01110: 01111: P0.0 P0.1 P0.2 P0.3 P0.4 P0.5 P0.6 P0.7 P1.0 P1.1 P1.2 P1.3 P1.4 P1.5 P1.6 Reserved, 11110: 11111: 11101: 10000: 10001: 10010: 10011: 10100: 10101: 10110: 10111: 11000: 11001: 11010: 11011: 11100: Reserved. Reserved. Reserved. Reserved. Reserved. Reserved. Reserved. Reserved. Reserved. Reserved. Reserved. Temperature Sensor VBAT Supply Voltage (0.9-1.8 V) or (1.8-3.6 V) Digital Supply Voltage (VREG0 Output, 1.7 V Typical) VDD/DC+ Supply Voltage (1.8-3.6 V) Ground
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5.8. Temperature Sensor
An on-chip temperature sensor is included on the C8051F91x-C8051F90x which can be directly accessed via the ADC multiplexer in single-ended configuration. To use the ADC to measure the temperature sensor, the ADC mux channel should select the temperature sensor. The temperature sensor transfer function is shown in Figure 5.8. The output voltage (VTEMP) is the positive ADC input when the ADC multiplexer is set correctly. The TEMPE bit in register REF0CN enables/disables the temperature sensor, as described in SFR Definition 5.15. While disabled, the temperature sensor defaults to a high impedance state and any ADC measurements performed on the sensor will result in meaningless data. Refer to Table 4.11 for the slope and offset parameters of the temperature sensor.
VTEMP = Slope x (TempC - 25) + Offset TempC = 25 + ( V TEMP - Offset) / Slope
Voltage
Slope ( V / deg C) Offset ( V at 25 Celsius)
Temperature
Figure 5.8. Temperature Sensor Transfer Function
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5.8.1. Calibration
The uncalibrated temperature sensor output is extremely linear and suitable for relative temperature measurements (see Table 4.11 for linearity specifications). For absolute temperature measurements, offset and/or gain calibration is recommended. Typically a 1-point (offset) calibration includes the following steps: 1. Control/measure the ambient temperature (this temperature must be known). 2. Power the device, and delay for a few seconds to allow for self-heating. 3. Perform an ADC conversion with the temperature sensor selected as the positive input and GND selected as the negative input. 4. Calculate the offset characteristics, and store this value in non-volatile memory for use with subsequent temperature sensor measurements. Figure 5.9 shows the typical temperature sensor error assuming a 1-point calibration at 25 C. Parameters that affect ADC measurement, in particular the voltage reference value, will also affect temperature measurement. A single-point offset measurement of the temperature sensor is performed on each device during production test. The measurement is performed at 25 C 5 C, using the ADC with the internal high speed reference buffer selected as the Voltage Reference. The direct ADC result of the measurement is stored in the SFR registers TOFFH and TOFFL, shown in SFR Definition 5.13 and SFR Definition 5.14.
5.00
5.00
4.00
4.00
3.00
3.00
2.00
2.00
Error (degrees C)
1.00
1.00
0.00 -40.00 -1.00
-20.00
0.00 20.00
40.00
60.00
0.00 80.00 -1.00
-2.00
-2.00
-3.00
-3.00
-4.00
-4.00
-5.00
-5.00
Temperature (degrees C)
Figure 5.9. Temperature Sensor Error with 1-Point Calibration (VREF = 1.68 V)
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SFR Definition 5.13. TOFFH: ADC0 Data Word High Byte
Bit Name Type Reset R Varies R Varies R Varies R Varies 7 6 5 4 TOFF[9:2] R Varies R Varies R Varies R Varies 3 2 1 0
SFR Page = 0xF; SFR Address = 0x86 Bit Name 7:0 TOFF[9:2]
Function
Temperature Sensor Offset High Bits. Most Significant Bits of the 10-bit temperature sensor offset measurement.
SFR Definition 5.14. TOFFL: ADC0 Data Word Low Byte
Bit Name Type Reset R Varies 7 TOFF[1:0] R Varies 0 0 0 0 0 0 6 5 4 3 2 1 0
SFR Page = 0xF; SFR Address = 0x85 Bit Name 7:6 5:0 TOFF[1:0] Unused
Function
Temperature Sensor Offset Low Bits. Least Significant Bits of the 10-bit temperature sensor offset measurement. Unused. Read = 0; Write = Don't Care.
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5.9. Voltage and Ground Reference Options
The voltage reference MUX is configurable to use an externally connected voltage reference, one of two internal voltage references, or one of two power supply voltages (see Figure 5.10). The ground reference MUX allows the ground reference for ADC0 to be selected between the ground pin (GND) or a port pin dedicated to analog ground (P0.1/AGND). The voltage and ground reference options are configured using the REF0CN SFR described on page 85. Electrical specifications are can be found in the Electrical Specifications Chapter. Important Note About the VREF and AGND Inputs: Port pins are used as the external VREF and AGND inputs. When using an external voltage reference or the internal precision reference, P0.0/VREF should be configured as an analog input and skipped by the Digital Crossbar. When using AGND as the ground reference to ADC0, P0.1/AGND should be configured as an analog input and skipped by the Digital Crossbar. Refer to Section "21. Port Input/Output" on page 205 for complete Port I/O configuration details. The external reference voltage must be within the range 0 VREF VDD/DC+ and the external ground reference must be at the same DC voltage potential as GND.
R E F 0C N REFGND REFSL1 REFSL0 TEMPE REFOE ADC Input M ux
T em p S ensor EN
REFOE
EN
VDD
R1
E xternal V oltage R eference C ircuit P 0 .0/V R E F V D D /D C +
Internal 1.68V R eference
00 01 Internal 1.8V R egulated D igital S upply Internal 1.65 V H igh S peed R eference 10 11 VREF (to A D C )
GND
4 .7 F
+
0 .1 F GND
0 R ecom m ended B ypass C apacitors P 0.1/A G N D 1
G round (to A D C )
REFGND
Figure 5.10. Voltage Reference Functional Block Diagram
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5.10. External Voltage References
To use an external voltage reference, REFSL[1:0] should be set to 00 and the internal 1.68 V precision reference should be disabled by setting REFOE to 0. Bypass capacitors should be added as recommended by the manufacturer of the external voltage reference.
5.11. Internal Voltage References
For applications requiring the maximum number of port I/O pins, or very short VREF turn-on time, the 1.65 V high-speed reference will be the best internal reference option to choose. The high speed internal reference is selected by setting REFSL[1:0] to 11. When selected, the high speed internal reference will be automatically enabled/disabled on an as-needed basis by ADC0. For applications requiring the highest absolute accuracy, the 1.68 V precision voltage reference will be the best internal reference option to choose. The 1.68 V precision reference may be enabled and selected by setting REFOE to 1 and REFSL[1:0] to 00. An external capacitor of at least 0.1 F is recommended when using the precision voltage reference. In applications that leave the precision internal oscillator always running, there is no additional power required to use the precision voltage reference. In all other applications, using the high speed reference will result in lower overall power consumption due to its minimal startup time and the fact that it remains in a low power state when an ADC conversion is not taking place.
Note: When using the precision internal oscillator as the system clock source, the precision voltage reference should not be enabled from a disabled state. To use the precision oscillator and the precision voltage reference simultaneously, the precision voltage reference should be enabled first and allowed to settle to its final value (charging the external capacitor) before the precision oscillator is started and selected as the system clock.
For applications with a non-varying power supply voltage, using the power supply as the voltage reference can provide ADC0 with added dynamic range at the cost of reduced power supply noise rejection. To use the 1.8 to 3.6 V power supply voltage (VDD/DC+) or the 1.8 V regulated digital supply voltage as the reference source, REFSL[1:0] should be set to 01 or 10, respectively.
5.12. Analog Ground Reference
To prevent ground noise generated by switching digital logic from affecting sensitive analog measurements, a separate analog ground reference option is available. When enabled, the ground reference for ADC0 during both the tracking/sampling and the conversion periods is taken from the P0.1/AGND pin. Any external sensors sampled by ADC0 should be referenced to the P0.1/AGND pin. This pin should be connected to the ground terminal of any external sensors sampled by ADC0. If an external voltage reference is used, the P0.1/AGND pin should be connected to the ground of the external reference and its associated decoupling capacitor. If the 1.68 V precision internal reference is used, then P0.1/AGND should be connected to the ground terminal of its external decoupling capacitor. The separate analog ground reference option is enabled by setting REFGND to 1. Note that when sampling the internal temperature sensor, the internal chip ground is always used for the sampling operation, regardless of the setting of the REFGND bit. Similarly, whenever the internal 1.65 V high-speed reference is selected, the internal chip ground is always used during the conversion period, regardless of the setting of the REFGND bit.
5.13. Temperature Sensor Enable
The TEMPE bit in register REF0CN enables/disables the temperature sensor. While disabled, the temperature sensor defaults to a high impedance state and any ADC0 measurements performed on the sensor result in meaningless data. See Section "5.8. Temperature Sensor" on page 80 for details on temperature sensor characteristics when it is enabled.
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SFR Definition 5.15. REF0CN: Voltage Reference Control
Bit Name Type Reset R 0 R 0 7 6 5 REFGND R/W 0 R/W 1 4 REFSL R/W 1 3 2 TEMPE R/W 0 R 0 1 0 REFOE R/W 0
SFR Page = 0x0; SFR Address = 0xD1 Bit Name 7:6 5 Unused Unused. Read = 00b; Write = Don't Care. REFGND Analog Ground Reference.
Function
Selects the ADC0 ground reference. 0: The ADC0 ground reference is the GND pin. 1: The ADC0 ground reference is the P0.1/AGND pin. 4:3 REFSL Voltage Reference Select. Selects the ADC0 voltage reference. 00: The ADC0 voltage reference is the P0.0/VREF pin. 01: The ADC0 voltage reference is the VDD/DC+ pin. 10: The ADC0 voltage reference is the internal 1.8 V digital supply voltage. 11: The ADC0 voltage reference is the internal 1.65 V high speed voltage reference. 2 TEMPE Temperature Sensor Enable. Enables/Disables the internal temperature sensor. 0: Temperature Sensor Disabled. 1: Temperature Sensor Enabled. 1 0 Unused REFOE Unused. Read = 0b; Write = Don't Care. Internal Voltage Reference Output Enable. Connects/Disconnects the internal voltage reference to the P0.0/VREF pin. 0: Internal 1.68 V Precision Voltage Reference disabled and not connected to P0.0/VREF. 1: Internal 1.68 V Precision Voltage Reference enabled and connected to P0.0/VREF.
5.14. Voltage Reference Electrical Specifications
See Table 4.12 on page 56 for detailed Voltage Reference Electrical Specifications.
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6. Programmable Current Reference (IREF0)
C8051F91x-C8051F90x devices include an on-chip programmable current reference (source or sink) with two output current settings: Low Power Mode and High Current Mode. The maximum current output in Low Power Mode is 63 A (1 A steps) and the maximum current output in High Current Mode is 504 A (8 A steps). The current source/sink is controlled though the IREF0CN special function register. It is enabled by setting the desired output current to a non-zero value. It is disabled by writing 0x00 to IREF0CN. The port I/O pin associated with ISRC0 should be configured as an analog input and skipped in the Crossbar. See Section "21. Port Input/Output" on page 205 for more details.
SFR Definition 6.1. IREF0CN: Current Reference Control
Bit Name Type Reset 7 SINK R/W 0 6 MODE R/W 0 0 0 0 5 4 3 IREF0DAT R/W 0 0 0 2 1 0
SFR Page = 0x0; SFR Address = 0xB9 Bit Name 7 SINK IREF0 Current Sink Enable.
Function
Selects if IREF0 is a current source or a current sink. 0: IREF0 is a current source. 1: IREF0 is a current sink. 6 MDSEL IREF0 Output Mode Select. Selects Low Power or High Current Mode. 0: Low Power Mode is selected (step size = 1 A). 1: High Current Mode is selected (step size = 8 A). 5:0 IREF0DAT[5:0] IREF0 Data Word. Specifies the number of steps required to achieve the desired output current. Output current = direction x step size x IREF0DAT. IREF0 is in a low power state when IREF0DAT is set to 0x00.
6.1.
PWM Enhanced Mode
On `F912 and `F902 devices, the precision of the current reference can be increased by fine tuning the IREF0 output using a PWM signal generated by the PCA. This mode allows the IREF0DAT bits to perform a course adjustment on the IREF0 output. Any available PCA channel can perform a fine adjustment on the IREF0 output. When enabled (PWMEN = 1), the CEX signal selected using the PWMSS bit field is internally routed to IREF0 to control the on time of a current source having the weight of 2 LSBs. With the two least significant bits of IREF0DAT set to 00b, applying a 100% duty cycle on the CEX signal will be equivalent to setting the two LSBs of IREF0DAT to 10b. PWM enhanced mode is enabled and setup using the IREF0CF register.
86
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SFR Definition 6.2. IREF0CF: Current Reference Configuration
Bit Name Type Reset 7 PWMEN R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 0 6 5 4 3 2 1 PWMSS[2:0] R/W 0 0 0
SFR Page = 0xF; SFR Address = 0xB9 Bit Name 7 PWMEN PWM Enhanced Mode Enable.
Function
Enables the PWM Enhanced Mode. Only available on `F912 and `F902 devices. 0: PWM Enhanced Mode disabled. 1: PWM Enhanced Mode enabled. 6:3 2:0 Unused PWMSS[2:0] Unused. Read = 00b, Write = don't care. PWM Source Select. Selects the PCA channel to use for the fine-tuning control signal. Only available on `F912 and `F902 devices. 000: CEX0 selected as fine-tuning control signal. 001: CEX1 selected as fine-tuning control signal. 010: CEX2 selected as fine-tuning control signal. 011: CEX3 selected as fine-tuning control signal. 100: CEX4 selected as fine-tuning control signal. 101: CEX5 selected as fine tuning control signal. All Other Values: Reserved.
6.2.
IREF0 Specifications
See Table 4.13 on page 57 for a detailed listing of IREF0 specifications.
Rev. 1.0
87
C8051F91x-C8051F90x
7. Comparators
C8051F91x-C8051F90x devices include two on-chip programmable voltage comparators: Comparator 0 (CPT0) is shown in Figure 7.1; Comparator 1 (CPT1) is shown in Figure 7.2. The two comparators operate identically, but may differ in their ability to be used as reset or wake-up sources. See the Reset Sources chapter and the Power Management chapter for details on reset sources and low power mode wake-up sources, respectively. The Comparator offers programmable response time and hysteresis, an analog input multiplexer, and two outputs that are optionally available at the Port pins: a digital synchronous "latched" output (CP0, CP1), or a digital asynchronous "raw" output (CP0A, CP1A). The asynchronous CP0A signal is available even when the system clock is not active. This allows the Comparator to operate and generate an output when the device is in some low power modes.
7.1.
Comparator Inputs
Each Comparator performs an analog comparison of the voltage levels at its positive (CP0+ or CP1+) and negative (CP0- or CP1-) input. Both comparators support multiple port pin inputs multiplexed to their positive and negative comparator inputs using analog input multiplexers. The analog input multiplexers are completely under software control and configured using SFR registers. See Section "7.6. Comparator0 and Comparator1 Analog Multiplexers" on page 95 for details on how to select and configure Comparator inputs. Important Note About Comparator Inputs: The Port pins selected as Comparator inputs should be configured as analog inputs and skipped by the Crossbar. See the Port I/O chapter for more details on how to configure Port I/O pins as Analog Inputs. The Comparator may also be used to compare the logic level of digital signals, however, Port I/O pins configured as digital inputs must be driven to a valid logic state (HIGH or LOW) to avoid increased power consumption.
CP0EN
CPT0CN
CP0OUT CP0RIF CP0FIF CP0HYP1 CP0HYP0 CP0HYN1 CP0HYN0
VDD
CP0 Interrupt
CPT0MD
CP0MD0 CP0MD1 CP0RIE CP0FIE CP0 Rising-edge CP0 Falling-edge
Analog Input Multiplexer Px.x
CP0 + Px.x
Interrupt Logic
+
D
SET
CP0
Q D
SET
Q
Px.x GND
CLR
Q
CLR
Q
Crossbar
(SYNCHRONIZER)
CP0 -
(ASYNCHRONOUS)
CP0A
Px.x
Reset Decision Tree
Figure 7.1. Comparator 0 Functional Block Diagram
88
Rev. 1.0
C8051F91x-C8051F90x
7.2. Comparator Outputs
When a comparator is enabled, its output is a logic 1 if the voltage at the positive input is higher than the voltage at the negative input. When disabled, the comparator output is a logic 0. The comparator output is synchronized with the system clock as shown in Figure 7.2. The synchronous "latched" output (CP0, CP1) can be polled in software (CPnOUT bit), used as an interrupt source, or routed to a Port pin (configured for digital I/O) through the Crossbar. The asynchronous "raw" comparator output (CP0A, CP1A) is used by the low power mode wake-up logic and reset decision logic. See the Power Options chapter and the Reset Sources chapter for more details on how the asynchronous comparator outputs are used to make wake-up and reset decisions. The asynchronous comparator output can also be routed directly to a Port pin through the Crossbar, and is available for use outside the device even if the system clock is stopped. When using a Comparator as an interrupt source, Comparator interrupts can be generated on rising-edge and/or falling-edge comparator output transitions. Two independent interrupt flags (CPnRIF and CPnFIF) allow software to determine which edge caused the Comparator interrupt. The comparator rising-edge and falling-edge interrupt flags are set by hardware when a corresponding edge is detected regardless of the interrupt enable state. Once set, these bits remain set until cleared by software. The rising-edge and falling-edge interrupts can be individually enabled using the CPnRIE and CPnFIE interrupt enable bits in the CPTnMD register. In order for the CPnRIF and/or CPnFIF interrupt flags to generate an interrupt request to the CPU, the Comparator must be enabled as an interrupt source and global interrupts must be enabled. See the Interrupt Handler chapter for additional information.
CP1EN
CPT0CN
CP1OUT CP1RIF CP1FIF CP1HYP1 CP1HYP0 CP1HYN1 CP1HYN0
VDD
CP1 Interrupt
CPT0MD
CP1MD0 CP1MD1 CP1RIE CP1FIE CP1 Rising-edge CP1 Falling-edge
Analog Input Multiplexer Px.x
CP1 + Px.x
Interrupt Logic
+
D
SET
CP1
Q D
SET
Q
Px.x GND
CLR
Q
CLR
Q
Crossbar
(SYNCHRONIZER)
CP1 -
(ASYNCHRONOUS)
CP1A
Px.x
Reset Decision Tree
Figure 7.2. Comparator 1 Functional Block Diagram
Rev. 1.0
89
C8051F91x-C8051F90x
7.3. Comparator Response Time
Comparator response time may be configured in software via the CPTnMD registers described on "CPT0MD: Comparator 0 Mode Selection" on page 92 and "CPT1MD: Comparator 1 Mode Selection" on page 94. Four response time settings are available: Mode 0 (Fastest Response Time), Mode 1, Mode 2, and Mode 3 (Lowest Power). Selecting a longer response time reduces the Comparator active supply current. The Comparators also have low power shutdown state, which is entered any time the comparator is disabled. Comparator rising edge and falling edge response times are typically not equal. See Table 4.14 on page 58 for complete comparator timing and supply current specifications.
7.4.
Comparator Hysteresis
The Comparators feature software-programmable hysteresis that can be used to stabilize the comparator output while a transition is occurring on the input. Using the CPTnCN registers, the user can program both the amount of hysteresis voltage (referred to the input voltage) and the positive and negative-going symmetry of this hysteresis around the threshold voltage (i.e., the comparator negative input). Figure 7.3 shows that when positive hysteresis is enabled, the comparator output does not transition from logic 0 to logic 1 until the comparator positive input voltage has exceeded the threshold voltage by an amount equal to the programmed hysteresis. It also shows that when negative hysteresis is enabled, the comparator output does not transition from logic 1 to logic 0 until the comparator positive input voltage has fallen below the threshold voltage by an amount equal to the programmed hysteresis. The amount of positive hysteresis is determined by the settings of the CPnHYP bits in the CPTnCN register and the amount of negative hysteresis voltage is determined by the settings of the CPnHYN bits in the same register. Settings of 20, 10, 5, or 0 mV can be programmed for both positive and negative hysteresis. See Section "Table 4.14. Comparator Electrical Characteristics" on page 58 for complete comparator hysteresis specifications.
VIN+ VIN-
CPn+ CPn-
+ CPn _
OUT
CIRCUIT CONFIGURATION
Positive Hysteresis Voltage (Programmed with CP0HYP Bits)
VIN-
INPUTS
VIN+
Negative Hysteresis Voltage (Programmed by CP0HYN Bits)
VOH
OUTPUT
VOL
Negative Hysteresis Disabled Positive Hysteresis Disabled Maximum Positive Hysteresis Maximum Negative Hysteresis
Figure 7.3. Comparator Hysteresis Plot
90
Rev. 1.0
C8051F91x-C8051F90x
7.5. Comparator Register Descriptions
The SFRs used to enable and configure the comparators are described in the following register descriptions. A Comparator must be enabled by setting the CPnEN bit to logic 1 before it can be used. From an enabled state, a comparator can be disabled and placed in a low power state by clearing the CPnEN bit to logic 0. Important Note About Comparator Settings: False rising and falling edges can be detected by the Comparator while powering on or if changes are made to the hysteresis or response time control bits. Therefore, it is recommended that the rising-edge and falling-edge flags be explicitly cleared to logic 0 a short time after the comparator is enabled or its mode bits have been changed. The Comparator Power Up Time is specified in Section "Table 4.14. Comparator Electrical Characteristics" on page 58.
SFR Definition 7.1. CPT0CN: Comparator 0 Control
Bit Name Type Reset 7 CP0EN R/W 0 6 CP0OUT R 0 5 CP0RIF R/W 0 4 CP0FIF R/W 0 0 3 2 1 0
CP0HYP[1:0] R/W 0
CP0HYN[1:0] R/W 0 0
SFR Page= 0x0; SFR Address = 0x9B Bit Name 7 CP0EN Comparator0 Enable Bit. 0: Comparator0 Disabled. 1: Comparator0 Enabled. 6 CP0OUT Comparator0 Output State Flag. 0: Voltage on CP0+ < CP0-. 1: Voltage on CP0+ > CP0-. 5 CP0RIF
Function
Comparator0 Rising-Edge Flag. Must be cleared by software. 0: No Comparator0 Rising Edge has occurred since this flag was last cleared. 1: Comparator0 Rising Edge has occurred.
4
CP0FIF
Comparator0 Falling-Edge Flag. Must be cleared by software. 0: No Comparator0 Falling-Edge has occurred since this flag was last cleared. 1: Comparator0 Falling-Edge has occurred.
3-2
CP0HYP[1:0] Comparator0 Positive Hysteresis Control Bits. 00: Positive Hysteresis Disabled. 01: Positive Hysteresis = Hysteresis 1. 10: Positive Hysteresis = Hysteresis 2. 11: Positive Hysteresis = Hysteresis 3 (Maximum).
1:0
CP0HYN[1:0] Comparator0 Negative Hysteresis Control Bits. 00: Negative Hysteresis Disabled. 01: Negative Hysteresis = Hysteresis 1. 10: Negative Hysteresis = Hysteresis 2. 11: Negative Hysteresis = Hysteresis 3 (Maximum).
Rev. 1.0
91
C8051F91x-C8051F90x
SFR Definition 7.2. CPT0MD: Comparator 0 Mode Selection
Bit Name Type Reset R/W 1 R 0 7 6 5 CP0RIE R/W 0 4 CP0FIE R/W 0 R 0 R 0 1 3 2 1 0
CP0MD[1:0] R/W 0
SFR Page = All Pages; SFR Address = 0x9D Bit Name 7 6 5 Reserved Unused CP0RIE Reserved. Read = 1b, Must Write 1b. Unused. Read = 0b, Write = don't care.
Function
Comparator0 Rising-Edge Interrupt Enable. 0: Comparator0 Rising-edge interrupt disabled. 1: Comparator0 Rising-edge interrupt enabled. Comparator0 Falling-Edge Interrupt Enable. 0: Comparator0 Falling-edge interrupt disabled. 1: Comparator0 Falling-edge interrupt enabled. Unused. Read = 00b, Write = don't care.
4
CP0FIE
3:2 1:0
Unused
CP0MD[1:0] Comparator0 Mode Select These bits affect the response time and power consumption for Comparator0. 00: Mode 0 (Fastest Response Time, Highest Power Consumption) 01: Mode 1 10: Mode 2 11: Mode 3 (Slowest Response Time, Lowest Power Consumption)
92
Rev. 1.0
C8051F91x-C8051F90x
SFR Definition 7.3. CPT1CN: Comparator 1 Control
Bit Name Type Reset 7 CP1EN R/W 0 6 CP1OUT R 0 5 CP1RIF R/W 0 4 CP1FIF R/W 0 0 3 2 1 0
CP1HYP[1:0] R/W 0
CP1HYN[1:0] R/W 0 0
SFR Page= 0x0; SFR Address = 0x9A
Bit
7
Name
CP1EN Comparator1 Enable Bit. 0: Comparator1 Disabled. 1: Comparator1 Enabled.
Function
6
CP1OUT
Comparator1 Output State Flag. 0: Voltage on CP1+ < CP1-. 1: Voltage on CP1+ > CP1-.
5
CP1RIF
Comparator1 Rising-Edge Flag. Must be cleared by software. 0: No Comparator1 Rising Edge has occurred since this flag was last cleared. 1: Comparator1 Rising Edge has occurred.
4
CP1FIF
Comparator1 Falling-Edge Flag. Must be cleared by software. 0: No Comparator1 Falling-Edge has occurred since this flag was last cleared. 1: Comparator1 Falling-Edge has occurred.
3:2
CP1HYP[1:0] Comparator1 Positive Hysteresis Control Bits. 00: Positive Hysteresis Disabled. 01: Positive Hysteresis = Hysteresis 1. 10: Positive Hysteresis = Hysteresis 2. 11: Positive Hysteresis = Hysteresis 3 (Maximum).
1:0
CP1HYN[1:0] Comparator1 Negative Hysteresis Control Bits. 00: Negative Hysteresis Disabled. 01: Negative Hysteresis = Hysteresis 1. 10: Negative Hysteresis = Hysteresis 2. 11: Negative Hysteresis = Hysteresis 3 (Maximum).
Rev. 1.0
93
C8051F91x-C8051F90x
SFR Definition 7.4. CPT1MD: Comparator 1 Mode Selection
Bit Name Type Reset R/W 1 R 0 7 6 5 CP1RIE R/W 0 4 CP1FIE R/W 0 R 0 R 0 1 3 2 1 0
CP1MD[1:0] R/W 0
SFR Page = 0x0; SFR Address = 0x9C
Bit
7 6 5
Name
Reserved Unused CP1RIE Reserved. Read = 1b, Must Write 1b. Unused. Read = 00b, Write = don't care.
Function
Comparator1 Rising-Edge Interrupt Enable. 0: Comparator1 Rising-edge interrupt disabled. 1: Comparator1 Rising-edge interrupt enabled. Comparator1 Falling-Edge Interrupt Enable. 0: Comparator1 Falling-edge interrupt disabled. 1: Comparator1 Falling-edge interrupt enabled. Unused. Read = 00b, Write = don't care.
4
CP1FIE
3:2 1:0
Unused
CP1MD[1:0] Comparator1 Mode Select These bits affect the response time and power consumption for Comparator1. 00: Mode 0 (Fastest Response Time, Highest Power Consumption) 01: Mode 1 10: Mode 2 11: Mode 3 (Slowest Response Time, Lowest Power Consumption)
94
Rev. 1.0
C8051F91x-C8051F90x
7.6. Comparator0 and Comparator1 Analog Multiplexers
Comparator0 and Comparator1 on C8051F91x-C8051F90x devices have analog input multiplexers to connect Port I/O pins and internal signals the comparator inputs; CP0+/CP0- are the positive and negative input multiplexers for Comparator0 and CP1+/CP1- are the positive and negative input multiplexers for Comparator1. The comparator input multiplexers directly support capacitive touch switches. When the Capacitive Touch Sense Compare input is selected on the positive or negative multiplexer, any Port I/O pin connected to the other multiplexer can be directly connected to a capacitive touch switch with no additional external components. The Capacitive Touch Sense Compare provides the appropriate reference level for detecting when the capacitive touch switches have charged or discharged through the on-chip Rsense resistor. The Comparator outputs can be routed to Timer2 or Timer3 for capturing sense capacitor's charge and discharge time. See Section "25. Timers" on page 270 for details. See Application Note AN338 for details on Capacitive Touch Switch sensing. Any of the following may be selected as comparator inputs: Port I/O pins, Capacitive Touch Sense Compare, VDD/DC+ Supply Voltage, Regulated Digital Supply Voltage (Output of VREG0), the VBAT Supply voltage or ground. The Comparator's supply voltage divided by 2 is also available as an input; the resistors used to divide the voltage only draw current when this setting is selected. The Comparator input multiplexers are configured using the CPT0MX and CPT1MX registers described in SFR Definition 7.5 and SFR Definition 7.6.
CPTnMX
CMXnN3 CMXnN2 CMXnN1 CMXnN0 CMXnP3 CMXnP2 CMXnP1 CMXnP0
P0.1 P0.3 P0.5 P0.7 P1.1 P1.3 P1.5
CPnOUT Rsense
VDD/DC+ CPnOUT R R VDD/DC+ R R R
Capacitive Touch Sense Compare
Only enabled when Capacitive Touch Sense Compare is selected on CPn+ Input MUX.
P0.0 P0.2 P0.4 P0.6 P1.0 P1.2 P1.4 P1.6
CPnOUT Rsense
Only enabled when Capacitive Touch Sense Compare is selected on CPnInput MUX. VDD/DC+
CPnInput MUX
VDD/DC+ CPnOUT R R VDD/DC+
(1/3 or 2/3) x VDD/DC+
Capacitive Touch Sense R Compare (1/3 or 2/3) x VDD/DC+
CPn+ Input MUX
+ GND
1/2 x VDD/DC+ Digital Supply VDD/DC+
R R
1/2 x VDD/DC+ VBAT
GND
Figure 7.4. CPn Multiplexer Block Diagram
Important Note About Comparator Input Configuration: Port pins selected as comparator inputs should be configured as analog inputs, and should be skipped by the Digital Crossbar. To configure a Port pin for analog input, set to 0 the corresponding bit in register PnMDIN and disable the digital driver (PnMDOUT = 0 and Port Latch = 1). To force the Crossbar to skip a Port pin, set to 1 the corresponding bit in register PnSKIP. See Section "21. Port Input/Output" on page 205 for more Port I/O configuration details.
Rev. 1.0
95
C8051F91x-C8051F90x
SFR Definition 7.5. CPT0MX: Comparator0 Input Channel Select
Bit Name Type Reset R/W 1 7 6 5 4 3 2 1 0
CMX0N[3:0] R/W 1 R/W 1 R/W 1 R/W 1
CMX0P[3:0] R/W 1 R/W 1 R/W 1
SFR Page = 0x0; SFR Address = 0x9F Bit Name 7:4 CMX0N
Function
Comparator0 Negative Input Selection. Selects the negative input channel for Comparator0. 0000: 0001: 0010: 0011: 0100: 0101: 0110: 0111: P0.1 P0.3 P0.5 P0.7 P1.1 P1.3 P1.5 Reserved 1000: 1001: 1010: 1011: 1100: 1101: 1110: 1111: Reserved Reserved Reserved Reserved Capacitive Touch Sense Compare VDD/DC+ divided by 2 Digital Supply Voltage Ground
3:0
CMX0P
Comparator0 Positive Input Selection. Selects the positive input channel for Comparator0. 0000: 0001: 0010: 0011: 0100: 0101: 0110: 0111: P0.0 P0.2 P0.4 P0.6 P1.0 P1.2 P1.4 P1.6 1000: 1001: 1010: 1011: 1100: 1101: 1110: 1111: Reserved Reserved Reserved Reserved Capacitive Touch Sense Compare VDD/DC+ divided by 2 VBAT Supply Voltage VDD/DC+ Supply Voltage
96
Rev. 1.0
C8051F91x-C8051F90x
SFR Definition 7.6. CPT1MX: Comparator1 Input Channel Select
Bit Name Type Reset R/W 1 7 6 5 4 3 2 1 0
CMX1N[3:0] R/W 1 R/W 1 R/W 1 R/W 1
CMX1P[3:0] R/W 1 R/W 1 R/W 1
SFR Page = 0x0; SFR Address = 0x9E Bit Name 7:4 CMX1N
Function
Comparator1 Negative Input Selection. Selects the negative input channel for Comparator1. 0000: 0001: 0010: 0011: 0100: 0101: 0110: 0111: P0.1 P0.3 P0.5 P0.7 P1.1 P1.3 P1.5 Reserved 1000: 1001: 1010: 1011: 1100: 1101: 1110: 1111: Reserved Reserved Reserved Reserved Capacitive Touch Sense Compare VDD/DC+ divided by 2 Digital Supply Voltage Ground
3:0
CMX1P
Comparator1 Positive Input Selection. Selects the positive input channel for Comparator1. 0000: 0001: 0010: 0011: 0100: 0101: 0110: 0111: P0.0 P0.2 P0.4 P0.6 P1.0 P1.2 P1.4 P1.6 1000: 1001: 1010: 1011: 1100: 1101: 1110: 1111: Reserved Reserved Reserved Reserved Capacitive Touch Sense Compare VDD/DC+ divided by 2 VBAT Supply Voltage VDD/DC+ Supply Voltage
Rev. 1.0
97
C8051F91x-C8051F90x
8. CIP-51 Microcontroller
The MCU system controller core is the CIP-51 microcontroller. The CIP-51 is fully compatible with the MCS-51TM instruction set; standard 803x/805x assemblers and compilers can be used to develop software. The MCU family has a superset of all the peripherals included with a standard 8051. The CIP-51 also includes on-chip debug hardware (see description in Section 27), and interfaces directly with the analog and digital subsystems providing a complete data acquisition or control-system solution in a single integrated circuit. The CIP-51 Microcontroller core implements the standard 8051 organization and peripherals as well as additional custom peripherals and functions to extend its capability (see Figure 8.1 for a block diagram). The CIP-51 includes the following features: - Fully Compatible with MCS-51 Instruction Set - 25 MIPS Peak Throughput with 25 MHz Clock - 0 to 25 MHz Clock Frequency Extended Interrupt Handler Reset Input Power Management Modes On-chip Debug Logic Program and Data Memory Security
8.1.
Performance
The CIP-51 employs a pipelined architecture that greatly increases its instruction throughput over the standard 8051 architecture. In a standard 8051, all instructions except for MUL and DIV take 12 or 24 system clock cycles to execute, and usually have a maximum system clock of 12 MHz. By contrast, the CIP-51 core executes 70% of its instructions in one or two system clock cycles, with no instructions taking more than eight system clock cycles.
DATA BUS
D8 D8 D8 D8 D8
ACCUMULATOR
B REGISTER
STACK POINTER
DATA BUS
TMP1
TMP2
PSW
ALU
D8 D8
SRAM ADDRESS REGISTER
D8
SRAM
DATA BUS
SFR_ADDRESS BUFFER
D8
DATA POINTER
D8 D8
SFR BUS INTERFACE
SFR_CONTROL SFR_WRITE_DATA SFR_READ_DATA
PC INCREMENTER
DATA BUS
D8
PROGRAM COUNTER (PC)
MEM_ADDRESS MEM_CONTROL
PRGM. ADDRESS REG.
A16
MEMORY INTERFACE
MEM_WRITE_DATA MEM_READ_DATA
PIPELINE RESET CLOCK STOP IDLE POWER CONTROL REGISTER
D8
D8
CONTROL LOGIC INTERRUPT INTERFACE
SYSTEM_IRQs EMULATION_IRQ
D8
Figure 8.1. CIP-51 Block Diagram
98
Rev. 1.0
D8
C8051F91x-C8051F90x
With the CIP-51's maximum system clock at 25 MHz, it has a peak throughput of 25 MIPS. The CIP-51 has a total of 109 instructions. The table below shows the total number of instructions that require each execution time. Clocks to Execute Number of Instructions 1 26 2 50 2/3 5 3 14 3/4 7 4 3 4/5 1 5 2 8 1
8.2.
Programming and Debugging Support
In-system programming of the Flash program memory and communication with on-chip debug support logic is accomplished via the Silicon Labs 2-Wire Development Interface (C2). The on-chip debug support logic facilitates full speed in-circuit debugging, allowing the setting of hardware breakpoints, starting, stopping and single stepping through program execution (including interrupt service routines), examination of the program's call stack, and reading/writing the contents of registers and memory. This method of on-chip debugging is completely non-intrusive, requiring no RAM, Stack, timers, or other on-chip resources. C2 details can be found in Section "27. C2 Interface" on page 312. The CIP-51 is supported by development tools from Silicon Labs and third party vendors. Silicon Labs provides an integrated development environment (IDE) including editor, debugger and programmer. The IDE's debugger and programmer interface to the CIP-51 via the C2 interface to provide fast and efficient in-system device programming and debugging. Third party macro assemblers and C compilers are also available.
8.3.
Instruction Set
The instruction set of the CIP-51 System Controller is fully compatible with the standard MCS-51TM instruction set. Standard 8051 development tools can be used to develop software for the CIP-51. All CIP51 instructions are the binary and functional equivalent of their MCS-51TM counterparts, including opcodes, addressing modes and effect on PSW flags. However, instruction timing is different than that of the standard 8051.
8.3.1. Instruction and CPU Timing
In many 8051 implementations, a distinction is made between machine cycles and clock cycles, with machine cycles varying from 2 to 12 clock cycles in length. However, the CIP-51 implementation is based solely on clock cycle timing. All instruction timings are specified in terms of clock cycles. Due to the pipelined architecture of the CIP-51, most instructions execute in the same number of clock cycles as there are program bytes in the instruction. Conditional branch instructions take one less clock cycle to complete when the branch is not taken as opposed to when the branch is taken. Table 8.1 is the CIP-51 Instruction Set Summary, which includes the mnemonic, number of bytes, and number of clock cycles for each instruction.
Rev. 1.0
99
C8051F91x-C8051F90x
Table 8.1. CIP-51 Instruction Set Summary
Mnemonic Description Arithmetic Operations Add register to A Add direct byte to A Add indirect RAM to A Add immediate to A Add register to A with carry Add direct byte to A with carry Add indirect RAM to A with carry Add immediate to A with carry Subtract register from A with borrow Subtract direct byte from A with borrow Subtract indirect RAM from A with borrow Subtract immediate from A with borrow Increment A Increment register Increment direct byte Increment indirect RAM Decrement A Decrement register Decrement direct byte Decrement indirect RAM Increment Data Pointer Multiply A and B Divide A by B Decimal adjust A Logical Operations AND Register to A AND direct byte to A AND indirect RAM to A AND immediate to A AND A to direct byte AND immediate to direct byte OR Register to A OR direct byte to A OR indirect RAM to A OR immediate to A OR A to direct byte OR immediate to direct byte Exclusive-OR Register to A Exclusive-OR direct byte to A Exclusive-OR indirect RAM to A Exclusive-OR immediate to A Exclusive-OR A to direct byte Exclusive-OR immediate to direct byte Bytes Clock Cycles 1 2 2 2 1 2 2 2 1 2 2 2 1 1 2 2 1 1 2 2 1 4 8 1 1 2 2 2 2 3 1 2 2 2 2 3 1 2 2 2 2 3
ADD A, Rn ADD A, direct ADD A, @Ri ADD A, #data ADDC A, Rn ADDC A, direct ADDC A, @Ri ADDC A, #data SUBB A, Rn SUBB A, direct SUBB A, @Ri SUBB A, #data INC A INC Rn INC direct INC @Ri DEC A DEC Rn DEC direct DEC @Ri INC DPTR MUL AB DIV AB DA A ANL A, Rn ANL A, direct ANL A, @Ri ANL A, #data ANL direct, A ANL direct, #data ORL A, Rn ORL A, direct ORL A, @Ri ORL A, #data ORL direct, A ORL direct, #data XRL A, Rn XRL A, direct XRL A, @Ri XRL A, #data XRL direct, A XRL direct, #data
1 2 1 2 1 2 1 2 1 2 1 2 1 1 2 1 1 1 2 1 1 1 1 1 1 2 1 2 2 3 1 2 1 2 2 3 1 2 1 2 2 3
100
Rev. 1.0
C8051F91x-C8051F90x
Table 8.1. CIP-51 Instruction Set Summary (Continued)
Mnemonic CLR A CPL A RL A RLC A RR A RRC A SWAP A MOV A, Rn MOV A, direct MOV A, @Ri MOV A, #data MOV Rn, A MOV Rn, direct MOV Rn, #data MOV direct, A MOV direct, Rn MOV direct, direct MOV direct, @Ri MOV direct, #data MOV @Ri, A MOV @Ri, direct MOV @Ri, #data MOV DPTR, #data16 MOVC A, @A+DPTR MOVC A, @A+PC MOVX A, @Ri MOVX @Ri, A MOVX A, @DPTR MOVX @DPTR, A PUSH direct POP direct XCH A, Rn XCH A, direct XCH A, @Ri XCHD A, @Ri CLR C CLR bit SETB C SETB bit CPL C CPL bit ANL C, bit Description Clear A Complement A Rotate A left Rotate A left through Carry Rotate A right Rotate A right through Carry Swap nibbles of A Data Transfer Move Register to A Move direct byte to A Move indirect RAM to A Move immediate to A Move A to Register Move direct byte to Register Move immediate to Register Move A to direct byte Move Register to direct byte Move direct byte to direct byte Move indirect RAM to direct byte Move immediate to direct byte Move A to indirect RAM Move direct byte to indirect RAM Move immediate to indirect RAM Load DPTR with 16-bit constant Move code byte relative DPTR to A Move code byte relative PC to A Move external data (8-bit address) to A Move A to external data (8-bit address) Move external data (16-bit address) to A Move A to external data (16-bit address) Push direct byte onto stack Pop direct byte from stack Exchange Register with A Exchange direct byte with A Exchange indirect RAM with A Exchange low nibble of indirect RAM with A Boolean Manipulation Clear Carry Clear direct bit Set Carry Set direct bit Complement Carry Complement direct bit AND direct bit to Carry Bytes 1 1 1 1 1 1 1 1 2 1 2 1 2 2 2 2 3 2 3 1 2 2 3 1 1 1 1 1 1 2 2 1 2 1 1 1 2 1 2 1 2 2 Clock Cycles 1 1 1 1 1 1 1 1 2 2 2 1 2 2 2 2 3 2 3 2 2 2 3 3 3 3 3 3 3 2 2 1 2 2 2 1 2 1 2 1 2 2
Rev. 1.0
101
C8051F91x-C8051F90x
Table 8.1. CIP-51 Instruction Set Summary (Continued)
Mnemonic ANL C, /bit ORL C, bit ORL C, /bit MOV C, bit MOV bit, C JC rel JNC rel JB bit, rel JNB bit, rel JBC bit, rel ACALL addr11 LCALL addr16 RET RETI AJMP addr11 LJMP addr16 SJMP rel JMP @A+DPTR JZ rel JNZ rel CJNE A, direct, rel CJNE A, #data, rel CJNE Rn, #data, rel CJNE @Ri, #data, rel DJNZ Rn, rel DJNZ direct, rel NOP Description AND complement of direct bit to Carry OR direct bit to carry OR complement of direct bit to Carry Move direct bit to Carry Move Carry to direct bit Jump if Carry is set Jump if Carry is not set Jump if direct bit is set Jump if direct bit is not set Jump if direct bit is set and clear bit Program Branching Absolute subroutine call Long subroutine call Return from subroutine Return from interrupt Absolute jump Long jump Short jump (relative address) Jump indirect relative to DPTR Jump if A equals zero Jump if A does not equal zero Compare direct byte to A and jump if not equal Compare immediate to A and jump if not equal Compare immediate to Register and jump if not equal Compare immediate to indirect and jump if not equal Decrement Register and jump if not zero Decrement direct byte and jump if not zero No operation Bytes 2 2 2 2 2 2 2 3 3 3 2 3 1 1 2 3 2 1 2 2 3 3 3 3 2 3 1 Clock Cycles 2 2 2 2 2 2/3 2/3 3/4 3/4 3/4 3 4 5 5 3 4 3 3 2/3 2/3 3/4 3/4 3/4 4/5 2/3 3/4 1
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Notes on Registers, Operands and Addressing Modes: Rn--Register R0-R7 of the currently selected register bank. @Ri--Data RAM location addressed indirectly through R0 or R1. rel--8-bit, signed (twos complement) offset relative to the first byte of the following instruction. Used by SJMP and all conditional jumps. direct--8-bit internal data location's address. This could be a direct-access Data RAM location (0x00-0x7F) or an SFR (0x80-0xFF). #data--8-bit constant #data16--16-bit constant bit--Direct-accessed bit in Data RAM or SFR addr11--11-bit destination address used by ACALL and AJMP. The destination must be within the same 2 kB page of program memory as the first byte of the following instruction. addr16--16-bit destination address used by LCALL and LJMP. The destination may be anywhere within the 8 kB program memory space. There is one unused opcode (0xA5) that performs the same function as NOP. All mnemonics copyrighted (c) Intel Corporation 1980.
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8.4. CIP-51 Register Descriptions
Following are descriptions of SFRs related to the operation of the CIP-51 System Controller. Reserved bits should not be set to logic l. Future product versions may use these bits to implement new features in which case the reset value of the bit will be logic 0, selecting the feature's default state. Detailed descriptions of the remaining SFRs are included in the sections of the data sheet associated with their corresponding system function.
SFR Definition 8.1. DPL: Data Pointer Low Byte
Bit Name Type Reset 0 0 0 0 7 6 5 4 DPL[7:0] R/W 0 0 0 0 3 2 1 0
SFR Page = All Pages; SFR Address = 0x82 Bit Name 7:0 DPL[7:0] Data Pointer Low.
Function
The DPL register is the low byte of the 16-bit DPTR. DPTR is used to access indirectly addressed Flash memory or XRAM.
SFR Definition 8.2. DPH: Data Pointer High Byte
Bit Name Type Reset 0 0 0 0 7 6 5 4 DPH[7:0] R/W 0 0 0 0 3 2 1 0
SFR Page = All Pages; SFR Address = 0x83 Bit Name 7:0 DPH[7:0] Data Pointer High.
Function
The DPH register is the high byte of the 16-bit DPTR. DPTR is used to access indirectly addressed Flash memory or XRAM.
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SFR Definition 8.3. SP: Stack Pointer
Bit Name Type Reset 0 0 0 0 7 6 5 4 SP[7:0] R/W 0 1 1 1 3 2 1 0
SFR Page = All Pages; SFR Address = 0x81 Bit Name 7:0 SP[7:0] Stack Pointer.
Function
The Stack Pointer holds the location of the top of the stack. The stack pointer is incremented before every PUSH operation. The SP register defaults to 0x07 after reset.
SFR Definition 8.4. ACC: Accumulator
Bit Name Type Reset 0 0 0 0 7 6 5 4 ACC[7:0] R/W 0 0 0 0 3 2 1 0
SFR Page = All Pages; SFR Address = 0xE0; Bit-Addressable Bit Name Function 7:0 ACC[7:0] Accumulator. This register is the accumulator for arithmetic operations.
SFR Definition 8.5. B: B Register
Bit Name Type Reset 0 0 0 0 7 6 5 4 B[7:0] R/W 0 0 0 0 3 2 1 0
SFR Page = All Pages; SFR Address = 0xF0; Bit-Addressable Bit Name Function 7:0 B[7:0] B Register. This register serves as a second accumulator for certain arithmetic operations.
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SFR Definition 8.6. PSW: Program Status Word
Bit Name Type Reset 7 CY R/W 0 6 AC R/W 0 5 F0 R/W 0 0 4 RS[1:0] R/W 0 3 2 OV R/W 0 1 F1 R/W 0 0 PARITY R 0
SFR Page = All Pages; SFR Address = 0xD0; Bit-Addressable Bit Name Function 7 CY Carry Flag. This bit is set when the last arithmetic operation resulted in a carry (addition) or a borrow (subtraction). It is cleared to logic 0 by all other arithmetic operations. 6 AC Auxiliary Carry Flag. This bit is set when the last arithmetic operation resulted in a carry into (addition) or a borrow from (subtraction) the high order nibble. It is cleared to logic 0 by all other arithmetic operations. 5 4:3 F0 RS[1:0] User Flag 0. This is a bit-addressable, general purpose flag for use under software control. Register Bank Select. These bits select which register bank is used during register accesses. 00: Bank 0, Addresses 0x00-0x07 01: Bank 1, Addresses 0x08-0x0F 10: Bank 2, Addresses 0x10-0x17 11: Bank 3, Addresses 0x18-0x1F 2 OV Overflow Flag. This bit is set to 1 under the following circumstances: * An ADD, ADDC, or SUBB instruction causes a sign-change overflow. * A MUL instruction results in an overflow (result is greater than 255). * A DIV instruction causes a divide-by-zero condition. The OV bit is cleared to 0 by the ADD, ADDC, SUBB, MUL, and DIV instructions in all other cases. 1 0 F1 PARITY User Flag 1. This is a bit-addressable, general purpose flag for use under software control. Parity Flag. This bit is set to logic 1 if the sum of the eight bits in the accumulator is odd and cleared if the sum is even.
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9. Memory Organization
The memory organization of the CIP-51 System Controller is similar to that of a standard 8051. There are two separate memory spaces: program memory and data memory. Program and data memory share the same address space but are accessed via different instruction types. The memory organization of the C8051F91x-C8051F90x device family is shown in Figure 9.1
PROGRAM/DATA MEMORY (FLASH)
DATA MEMORY (RAM) INTERNAL DATA ADDRESS SPACE
Special Function Registers (Indirect Addressing Only) (Direct Addressing Only) (Direct and Indirect Addressing) Bit Addressable General Purpose Registers Lower 128 RAM (Direct and Indirect Addressing) Upper 128 RAM
C8051F912/11
0x01FF 0x0000 0x3FFF 0x3C00 0x3BFF 16KB FLASH (In-System Programmable in 512 Byte Sectors) 0x0000 Scrachpad Memory (DATA only) RESERVED
0
F
EXTERNAL DATA ADDRESS SPACE C8051F902/1 C8051F912/11/02/01
0x1FFF
0x01FF 0x0000 0x1FFF
Scrachpad Memory (DATA only)
Unpopulated Address Space
8KB FLASH (In-System Programmable in 512 Byte Sectors) 0x0000 0x0000
0x0200 0x01FF
XRAM - 512 Bytes
(accessable using MOVX instruction)
Note: Code compatible devices with up to 64 kB Flash and 4 kB RAM are available as the C8051F93x-92x family.
Figure 9.1. C8051F91x-C8051F90x Memory Map
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9.1. Program Memory
The CIP-51 core has a 64 kB program memory space. The C8051F91x-C8051F90x devices implement 16 kB (C8051F912/1) or 8 kB (C8051F902/1) of this program memory space as in-system, reprogrammable Flash memory, organized in a contiguous block from addresses 0x0000 to 0x3BFF (C8051F912/1) or 0x1FFF (C8051F902/1). The last byte of this contiguous block of addresses serves as the security lock byte for the device. Any addresses above the lock byte are reserved.
C8051F912/1 (SFLE=0)
0xFFFF
C8051F902/1 (SFLE=0)
0xFFFF
Reserved Area
0x3C00
0x3BFE
Lock Byte Page
0x3A00 0x39FF
0x8000
Lock Byte
0x1FFF 0x1FFE
C8051F912/1 C8051F902/1 (SFLE=1)
0x01FF
Flash Memory Space
Lock Byte Page
0x1E00 0x1BFF
Scratchpad (Data Only)
0x0000 0x0000
Flash Memory Space
0x0000
Figure 9.2. Flash Program Memory Map 9.1.1. MOVX Instruction and Program Memory
The MOVX instruction in an 8051 device is typically used to access external data memory. On the C8051F91x-C8051F90x devices, the MOVX instruction is normally used to read and write on-chip XRAM, but can be re-configured to write and erase on-chip Flash memory space. MOVC instructions are always used to read Flash memory, while MOVX write instructions are used to erase and write Flash. This Flash access feature provides a mechanism for the C8051F91x-C8051F90x to update program code and use the program memory space for non-volatile data storage. Refer to Section "13. Flash Memory" on page 132 for further details.
9.2.
Data Memory
The C8051F91x-C8051F90x device family include 768 bytes of RAM data memory. 256 bytes of this memory is mapped into the internal RAM space of the 8051. The remainder of this memory is on-chip "external" memory. The data memory map is shown in Figure 9.1 for reference.
9.2.1. Internal RAM
There are 256 bytes of internal RAM mapped into the data memory space from 0x00 through 0xFF. The lower 128 bytes of data memory are used for general purpose registers and scratch pad memory. Either direct or indirect addressing may be used to access the lower 128 bytes of data memory. Locations 0x00 through 0x1F are addressable as four banks of general purpose registers, each bank consisting of eight byte-wide registers. The next 16 bytes, locations 0x20 through 0x2F, may either be addressed as bytes or as 128 bit locations accessible with the direct addressing mode. The upper 128 bytes of data memory are accessible only by indirect addressing. This region occupies the same address space as the Special Function Registers (SFR) but is physically separate from the SFR space. The addressing mode used by an instruction when accessing locations above 0x7F determines
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Lock Byte
0x3BFF
Unpopulated Address Space (Reserved)
C8051F91x-C8051F90x
whether the CPU accesses the upper 128 bytes of data memory space or the SFRs. Instructions that use direct addressing will access the SFR space. Instructions using indirect addressing above 0x7F access the upper 128 bytes of data memory. Figure 9.1 illustrates the data memory organization of the C8051F91xC8051F90x. 9.2.1.1. General Purpose Registers The lower 32 bytes of data memory, locations 0x00 through 0x1F, may be addressed as four banks of general-purpose registers. Each bank consists of eight byte-wide registers designated R0 through R7. Only one of these banks may be enabled at a time. Two bits in the program status word, RS0 (PSW.3) and RS1 (PSW.4), select the active register bank (see description of the PSW in SFR Definition 8.6). This allows fast context switching when entering subroutines and interrupt service routines. Indirect addressing modes use registers R0 and R1 as index registers. 9.2.1.2. Bit Addressable Locations In addition to direct access to data memory organized as bytes, the sixteen data memory locations at 0x20 through 0x2F are also accessible as 128 individually addressable bits. Each bit has a bit address from 0x00 to 0x7F. Bit 0 of the byte at 0x20 has bit address 0x00 while bit7 of the byte at 0x20 has bit address 0x07. Bit 7 of the byte at 0x2F has bit address 0x7F. A bit access is distinguished from a full byte access by the type of instruction used (bit source or destination operands as opposed to a byte source or destination). The MCS-51TM assembly language allows an alternate notation for bit addressing of the form XX.B where XX is the byte address and B is the bit position within the byte. For example, the instruction:
MOV C, 22.3h
moves the Boolean value at 0x13 (bit 3 of the byte at location 0x22) into the Carry flag.
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9.2.1.3. Stack A programmer's stack can be located anywhere in the 256-byte data memory. The stack area is designated using the Stack Pointer (SP) SFR. The SP will point to the last location used. The next value pushed on the stack is placed at SP+1 and then SP is incremented. A reset initializes the stack pointer to location 0x07. Therefore, the first value pushed on the stack is placed at location 0x08, which is also the first register (R0) of register bank 1. Thus, if more than one register bank is to be used, the SP should be initialized to a location in the data memory not being used for data storage. The stack depth can extend up to 256 bytes.
9.2.2. External RAM
There are 512 bytes of on-chip RAM mapped into the external data memory space. All of these address locations may be accessed using the external move instruction (MOVX) and the data pointer (DPTR), or using MOVX indirect addressing mode (such as @R1) in combination with the EMI0CN register.
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10. On-Chip XRAM
The C8051F91x-C8051F90x MCUs include on-chip RAM mapped into the external data memory space (XRAM). The external memory space may be accessed using the external move instruction (MOVX) with the target address specified in either the data pointer (DPTR), or with the target address low byte in R0 or R1 and the target address high byte in the External Memory Interface Control Register (EMI0CN, shown in SFR Definition 10.1). When using the MOVX instruction to access on-chip RAM, no additional initialization is required and the MOVX instruction execution time is as specified in the CIP-51 chapter. Important Note: MOVX write operations can be configured to target Flash memory, instead of XRAM. See Section "13. Flash Memory" on page 132 for more details. The MOVX instruction accesses XRAM by default.
10.1. Accessing XRAM
The XRAM memory space is accessed using the MOVX instruction. The MOVX instruction has two forms, both of which use an indirect addressing method. The first method uses the Data Pointer, DPTR, a 16-bit register which contains the effective address of the XRAM location to be read from or written to. The second method uses R0 or R1 in combination with the EMI0CN register to generate the effective XRAM address. Examples of both of these methods are given below.
10.1.1. 16-Bit MOVX Example
The 16-bit form of the MOVX instruction accesses the memory location pointed to by the contents of the DPTR register. The following series of instructions reads the value of the byte at address 0x1234 into the accumulator A:
MOV MOVX DPTR, #1234h A, @DPTR ; load DPTR with 16-bit address to read (0x1234) ; load contents of 0x1234 into accumulator A
The above example uses the 16-bit immediate MOV instruction to set the contents of DPTR. Alternately, the DPTR can be accessed through the SFR registers DPH, which contains the upper 8-bits of DPTR, and DPL, which contains the lower 8-bits of DPTR.
10.1.2. 8-Bit MOVX Example
The 8-bit form of the MOVX instruction uses the contents of the EMI0CN SFR to determine the upper 8-bits of the effective address to be accessed and the contents of R0 or R1 to determine the lower 8-bits of the effective address to be accessed. The following series of instructions read the contents of the byte at address 0x1234 into the accumulator A.
MOV MOV MOVX EMI0CN, #12h R0, #34h a, @R0 ; load high byte of address into EMI0CN ; load low byte of address into R0 (or R1) ; load contents of 0x1234 into accumulator A
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10.2. Special Function Registers
The special function register used for configuring XRAM access is EMI0CN.
SFR Definition 10.1. EMI0CN: External Memory Interface Control
Bit Name Type Reset R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 7 6 5 4 3 2 1 0 PGSEL R/W 0
SFR Page = 0x0; SFR Address = 0xAA
Bit
7:1 0
Name
Unused PGSEL Unused.
Function
Read = 0000000b; Write = Don't Care XRAM Page Select. The EMI0CN register provides the high byte of the 16-bit external data memory address when using an 8-bit MOVX command, effectively selecting a 256-byte page of RAM. Since the upper (unused) bits of the register are always zero, the PGSEL determines which page of XRAM is accessed. For Example: If EMI0CN = 0x01, addresses 0x0100 through 0x01FF will be accessed. If EMI0CN = 0x00, addresses 0x0000 through 0x00FF will be accessed.
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11. Special Function Registers
The direct-access data memory locations from 0x80 to 0xFF constitute the special function registers (SFRs). The SFRs provide control and data exchange with the C8051F91x-C8051F90x's resources and peripherals. The CIP-51 controller core duplicates the SFRs found in a typical 8051 implementation as well as implementing additional SFRs used to configure and access the sub-systems unique to the C8051F91x-C8051F90x. This allows the addition of new functionality while retaining compatibility with the MCS-51TM instruction set. Table 11.1 and Table 11.2 list the SFRs implemented in the C8051F91xC8051F90x device family. The SFR registers are accessed anytime the direct addressing mode is used to access memory locations from 0x80 to 0xFF. SFRs with addresses ending in 0x0 or 0x8 (e.g., P0, TCON, SCON0, IE, etc.) are bitaddressable as well as byte-addressable. All other SFRs are byte-addressable only. Unoccupied addresses in the SFR space are reserved for future use. Accessing these areas will have an indeterminate effect and should be avoided. Refer to the corresponding pages of the data sheet, as indicated in Table 11.3, for a detailed description of each register.
Table 11.1. Special Function Register (SFR) Memory Map (Page 0x0)
F8 F0 E8 E0 D8 D0 C8 C0 B8 B0 A8 A0 98 90 88 80 SPI0CN PCA0L PCA0H PCA0CPL0 PCA0CPH0 B P0MDIN P1MDIN SMB0ADR ADC0CN PCA0CPL1 PCA0CPH1 PCA0CPL2 PCA0CPH2 ACC XBR0 XBR1 XBR2 IT01CF PCA0CN PCA0MD PCA0CPM0 PCA0CPM1 PCA0CPM2 PSW REF0CN PCA0CPL5 PCA0CPH5 P0SKIP TMR2CN REG0CN TMR2RLL TMR2RLH TMR2L SMB0CN SMB0CF SMB0DAT ADC0GTL ADC0GTH IP IREF0CN ADC0AC ADC0MX ADC0CF SPI1CN OSCXCN OSCICN OSCICL IE CLKSEL EMI0CN RTC0ADR P2 SPI0CFG SPI0CKR SPI0DAT P0MDOUT SCON0 SBUF0 CPT1CN CPT0CN CPT1MD P1 TMR3CN TMR3RLL TMR3RLH TMR3L TCON TMOD TL0 TL1 TH0 P0 SP DPL DPH SPI1CFG 0(8) 1(9) 2(A) 3(B) 4(C) (bit addressable) PCA0CPL4 SMB0ADM PCA0CPL3 FLWR PCA0CPM3 P1SKIP TMR2H ADC0LTL ADC0L PMU0CF RTC0DAT P1MDOUT CPT0MD TMR3H TH1 SPI1CKR 5(D) PCA0CPH4 VDM0CN EIP1 EIP2 PCA0CPH3 RSTSRC EIE1 EIE2 PCA0CPM4 PCA0PWM P0MAT PCA0CPM5 P1MAT ADC0LTH P0MASK ADC0H P1MASK FLSCL FLKEY RTC0KEY P2MDOUT SFRPAGE CPT1MX CPT0MX DC0CF DC0CN CKCON PSCTL SPI1DAT PCON 6(E) 7(F)
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11.1. SFR Paging
To accommodate more than 128 SFRs in the 0x80 to 0xFF address space, SFR paging has been implemented. By default, all SFR accesses target SFR Page 0x0 to allow access to the registers listed in Table 11.1. During device initialization, some SFRs located on SFR Page 0xF may need to be accessed. Table 11.2 lists the SFRs accessible from SFR Page 0x0F. Some SFRs are accessible from both pages, including the SFRPAGE register. SFRs only accessible from Page 0xF are in bold. SFRs only available on the `F912 and `F902 devices are in blue. The following procedure should be used when accessing SFRs on Page 0xF: 1. 2. 3. 4. 5. 6. Save the current interrupt state (EA_save = EA). Disable Interrupts (EA = 0). Set SFRPAGE = 0xF. Access the SFRs located on SFR Page 0xF. Set SFRPAGE = 0x0. Restore interrupt state (EA = EA_save).
Table 11.2. Special Function Register (SFR) Memory Map (Page 0xF)
F8 F0 E8 E0 D8 D0 C8 C0 B8 B0 A8 A0 98 90 88 80 B ACC PSW FLWR EIP1 EIE1 EIP2 EIE2
IREF0CF ADC0PWR IE P2 P1 CLKSEL P0DRV CRC0DAT CRC0CN DPL 2(A) CRC0IN DPH 3(B) DC0MD
ADC0TK PMU0MD P1DRV CRC0FLIP TOFFL 5(D) P2DRV SFRPAGE
CRC0AUTO CRC0CNT TOFFH 6(E) PCON 7(F)
P0 SP 0(8) 1(9) (bit addressable)
4(C)
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SFR Definition 11.1. SFR Page: SFR Page
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
SFRPAGE[7:0] R/W 0 0 0 0
SFR Page = All Pages; SFR Address = 0xA7 Bit Name 7:0 SFRPAGE[7:0] SFR Page.
Function
Specifies the SFR Page used when reading, writing, or modifying special function registers.
Table 11.3. Special Function Registers
SFRs are listed in alphabetical order. All undefined SFR locations are reserved. SFRs highlighted in blue are only available on `F912 and `F902 devices. Register ACC ADC0AC ADC0CF ADC0CN ADC0GTH ADC0GTL ADC0H ADC0L ADC0LTH ADC0LTL ADC0MX ADC0PWR ADC0TK B CKCON CLKSEL CPT0CN CPT0MD CPT0MX CPT1CN Address 0xE0 0xBA 0xBC 0xE8 0xC4 0xC3 0xBE 0xBD 0xC6 0xC5 0xBB 0xBA 0xBD 0xF0 0x8E 0xA9 0x9B 0x9D 0x9F 0x9A SFR Page All 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0xF 0xF All 0x0 All 0x0 0x0 0x0 0x0 Accumulator ADC0 Accumulator Configuration ADC0 Configuration ADC0 Control ADC0 Greater-Than Compare High ADC0 Greater-Than Compare Low ADC0 High ADC0 Low ADC0 Less-Than Compare Word High ADC0 Less-Than Compare Word Low AMUX0 Channel Select ADC0 Burst Mode Power-Up Time ADC0 Tracking Control B Register Clock Control Clock Select Comparator0 Control Comparator0 Mode Selection Comparator0 Mux Selection Comparator1 Control Description Page 105 71 70 69 75 75 74 74 76 76 79 72 73 105 271 185 92 92 96 93
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Table 11.3. Special Function Registers (Continued)
SFRs are listed in alphabetical order. All undefined SFR locations are reserved. SFRs highlighted in blue are only available on `F912 and `F902 devices. Register CPT1MD CPT1MX CRC0AUTO CRC0CN CRC0CNT CRC0DAT CRC0FLIP CRC0IN DC0CF DC0CN DC0MD DPH DPL EIE1 EIE2 EIP1 EIP2 EMI0CN FLKEY FLSCL IE IP IREF0CN IREF0CF IT01CF OSCICL OSCICN OSCXCN P0 P0DRV P0MASK P0MAT P0MDIN Address 0x9C 0x9E 0x96 0x92 0x97 0x91 0x95 0x93 0x96 0x97 0x94 0x83 0x82 0xE6 0xE7 0xF6 0xF7 0xAA 0xB7 0xB6 0xA8 0xB8 0xB9 0xB9 0xE4 0xB3 0xB2 0xB1 0x80 0xA4 0xC7 0xD7 0xF1 SFR Page 0x0 0x0 0xF 0xF 0xF 0xF 0xF 0xF 0x0 0x0 0xF All All All All 0x0 0x0 0x0 0x0 0x0 All 0x0 0x0 0xF 0x0 0x0 0x0 0x0 All 0xF 0x0 0x0 0x0 Description Comparator1 Mode Selection Comparator1 Mux Selection CRC0 Automatic Control CRC0 Control CRC0 Automatic Flash Sector Count CRC0 Data CRC0 Flip CRC0 Input DC0 (DC-DC Converter) Configuration DC0 (DC-DC Converter) Control DC0 (DC-DC Converter) Mode Data Pointer High Data Pointer Low Extended Interrupt Enable 1 Extended Interrupt Enable 2 Extended Interrupt Priority 1 Extended Interrupt Priority 2 EMIF Control Flash Lock And Key Flash Scale Interrupt Enable Interrupt Priority Current Reference IREF Control Current Reference IREF Configuration INT0/INT1 Configuration Internal Oscillator Calibration Internal Oscillator Control External Oscillator Control Port 0 Latch Port 0 Drive Strength Port 0 Mask Port 0 Match Port 0 Input Mode Configuration Page 94 97 157 155 158 156 159 156 168 167 169 104 104 126 128 127 129 112 141 141 124 125 86 87 131 186 186 187 218 220 215 215 219
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Table 11.3. Special Function Registers (Continued)
SFRs are listed in alphabetical order. All undefined SFR locations are reserved. SFRs highlighted in blue are only available on `F912 and `F902 devices. Register P0MDOUT P0SKIP P1 P1DRV P1MASK P1MAT P1MDIN P1MDOUT P1SKIP P2 P2DRV P2MDOUT PCA0CN PCA0CPH0 PCA0CPH1 PCA0CPH2 PCA0CPH3 PCA0CPH4 PCA0CPH5 PCA0CPL0 PCA0CPL1 PCA0CPL2 PCA0CPL3 PCA0CPL4 PCA0CPL5 PCA0CPM0 PCA0CPM1 PCA0CPM2 PCA0CPM3 PCA0CPM4 PCA0CPM5 PCA0H PCA0L Address 0xA4 0xD4 0x90 0xA5 0xBF 0xCF 0xF2 0xA5 0xD5 0xA0 0xA6 0xA6 0xD8 0xFC 0xEA 0xEC 0xEE 0xFE 0xD3 0xFB 0xE9 0xEB 0xED 0xFD 0xD2 0xDA 0xDB 0xDC 0xDD 0xDE 0xCE 0xFA 0xF9 SFR Page 0x0 0x0 All 0xF 0x0 0x0 0x0 0x0 0x0 All 0xF 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 Port 0 Skip Port 1 Latch Port 1 Drive Strength Port 1 Mask Port 1 Match Port 1 Input Mode Configuration Port 1 Output Mode Configuration Port 1 Skip Port 2 Latch Port 2 Drive Strength Port 2 Output Mode Configuration PCA0 Control PCA0 Capture 0 High PCA0 Capture 1 High PCA0 Capture 2 High PCA0 Capture 3 High PCA0 Capture 4 High PCA0 Capture 5 High PCA0 Capture 0 Low PCA0 Capture 1 Low PCA0 Capture 2 Low PCA0 Capture 3 Low PCA0 Capture 4 Low PCA0 Capture 5 Low PCA0 Module 0 Mode Register PCA0 Module 1 Mode Register PCA0 Module 2 Mode Register PCA0 Module 3 Mode Register PCA0 Module 4 Mode Register PCA0 Module 5 Mode Register PCA0 Counter High PCA0 Counter Low Description Port 0 Output Mode Configuration Page 219 218 221 223 216 216 222 222 221 223 224 224 306 311 311 311 311 311 311 311 311 311 311 311 311 309 309 309 309 309 309 310 310
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Table 11.3. Special Function Registers (Continued)
SFRs are listed in alphabetical order. All undefined SFR locations are reserved. SFRs highlighted in blue are only available on `F912 and `F902 devices. Register PCA0MD PCA0PWM PCON PMU0CF PMU0MD PSCTL PSW REF0CN REG0CN RSTSRC RTC0ADR RTC0DAT RTC0KEY SBUF0 SCON0 SFRPAGE SMB0ADM SMB0ADR SMB0CF SMB0CN SMB0DAT SP SPI0CFG SPI0CKR SPI0CN SPI0DAT SPI1CFG SPI1CKR SPI1CN SPI1DAT TCON TH0 TH1 Address 0xD9 0xDF 0x87 0xB5 0xB5 0x8F 0xD0 0xD1 0xC9 0xEF 0xAC 0xAD 0xAE 0x99 0x98 0xA7 0xF5 0xF4 0xC1 0xC0 0xC2 0x81 0xA1 0xA2 0xF8 0xA3 0x84 0x85 0xB0 0x86 0x88 0x8C 0x8D SFR Page 0x0 0x0 0x0 0x0 0xF 0x0 All 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 All 0x0 0x0 0x0 0x0 0x0 All 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 PCA0 Mode PCA0 PWM Configuration Power Control PMU0 Configuration PMU0 Mode Program Store R/W Control Program Status Word Voltage Reference Control Voltage Regulator (VREG0) Control Reset Source Configuration/Status RTC0 Address RTC0 Data RTC0 Key UART0 Data Buffer UART0 Control SFR Page SMBus Slave Address Mask SMBus Slave Address SMBus Configuration SMBus Control SMBus Data Stack Pointer SPI0 Configuration SPI0 Clock Rate Control SPI0 Control SPI0 Data SPI1 Configuration SPI1 Clock Rate Control SPI1 Control SPI1 Data Timer/Counter Control Timer/Counter 0 High Timer/Counter 1 High Description Page 307 308 151 149 150 140 106 85 170 178 193 193 192 253 252 115 237 237 232 234 238 105 263 265 264 266 263 265 264 266 276 279 279
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Table 11.3. Special Function Registers (Continued)
SFRs are listed in alphabetical order. All undefined SFR locations are reserved. SFRs highlighted in blue are only available on `F912 and `F902 devices. Register TL0 TL1 TMOD TMR2CN TMR2H TMR2L TMR2RLH TMR2RLL TMR3CN TMR3H TMR3L TMR3RLH TMR3RLL TOFFH TOFFL VDM0CN XBR0 XBR1 XBR2 Address 0x8A 0x8B 0x89 0xC8 0xCD 0xCC 0xCB 0xCA 0x91 0x95 0x94 0x93 0x92 0x86 0x85 0xFF 0xE1 0xE2 0xE3 SFR Page 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0xF 0xF 0x0 0x0 0x0 0x0 Timer/Counter 0 Low Timer/Counter 1 Low Timer/Counter Mode Timer/Counter 2 Control Timer/Counter 2 High Timer/Counter 2 Low Timer/Counter 2 Reload High Timer/Counter 2 Reload Low Timer/Counter 3 Control Timer/Counter 3 High Timer/Counter 3 Low Timer/Counter 3 Reload High Timer/Counter 3 Reload Low Temperature Offset High Temperature Offset Low VDD Monitor Control Port I/O Crossbar Control 0 Port I/O Crossbar Control 1 Port I/O Crossbar Control 2 Description Page 278 278 277 283 285 285 284 284 289 291 291 290 290 82 82 175 212 213 214
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12. Interrupt Handler
The C8051F91x-C8051F90x microcontroller family includes an extended interrupt system supporting multiple interrupt sources and two priority levels. The allocation of interrupt sources between on-chip peripherals and external input pins varies according to the specific version of the device. Refer to Table 12.1, "Interrupt Summary," on page 122 for a detailed listing of all interrupt sources supported by the device. Refer to the data sheet section associated with a particular on-chip peripheral for information regarding valid interrupt conditions for the peripheral and the behavior of its interrupt-pending flag(s). Each interrupt source has one or more associated interrupt-pending flag(s) located in an SFR or an indirect register. When a peripheral or external source meets a valid interrupt condition, the associated interrupt-pending flag is set to logic 1. If both global interrupts and the specific interrupt source is enabled, a CPU interrupt request is generated when the interrupt-pending flag is set. As soon as execution of the current instruction is complete, the CPU generates an LCALL to a predetermined address to begin execution of an interrupt service routine (ISR). Each ISR must end with an RETI instruction, which returns program execution to the next instruction that would have been executed if the interrupt request had not occurred. If interrupts are not enabled, the interrupt-pending flag is ignored by the hardware and program execution continues as normal. (The interrupt-pending flag is set to logic 1 regardless of the interrupt's enable/disable state.) Some interrupt-pending flags are automatically cleared by hardware when the CPU vectors to the ISR. However, most are not cleared by the hardware and must be cleared by software before returning from the ISR. If an interrupt-pending flag remains set after the CPU completes the return-from-interrupt (RETI) instruction, a new interrupt request will be generated immediately and the CPU will re-enter the ISR after the completion of the next instruction.
12.1. Enabling Interrupt Sources
Each interrupt source can be individually enabled or disabled through the use of an associated interrupt enable bit in the Interrupt Enable and Extended Interrupt Enable SFRs. However, interrupts must first be globally enabled by setting the EA bit (IE.7) to logic 1 before the individual interrupt enables are recognized. Setting the EA bit to logic 0 disables all interrupt sources regardless of the individual interruptenable settings. Note that interrupts which occur when the EA bit is set to logic 0 will be held in a pending state, and will not be serviced until the EA bit is set back to logic 1.
12.2. MCU Interrupt Sources and Vectors
The CPU services interrupts by generating an LCALL to a predetermined address (the interrupt vector address) to begin execution of an interrupt service routine (ISR). The interrupt vector addresses associated with each interrupt source are listed in Table 12.1 on page 122. Software should ensure that the interrupt vector for each enabled interrupt source contains a valid interrupt service routine. Software can simulate an interrupt by setting any interrupt-pending flag to logic 1. If interrupts are enabled for the flag, an interrupt request will be generated and the CPU will vector to the ISR address associated with the interrupt-pending flag.
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12.3. Interrupt Priorities
Each interrupt source can be individually programmed to one of two priority levels: low or high. A low priority interrupt service routine can be preempted by a high priority interrupt. A high priority interrupt cannot be preempted. If a high priority interrupt preempts a low priority interrupt, the low priority interrupt will finish execution after the high priority interrupt completes. Each interrupt has an associated interrupt priority bit in in the Interrupt Priority and Extended Interrupt Priority registers used to configure its priority level. Low priority is the default. If two interrupts are recognized simultaneously, the interrupt with the higher priority is serviced first. If both interrupts have the same priority level, a fixed priority order is used to arbitrate. See Table 12.1 on page 122 to determine the fixed priority order used to arbitrate between simultaneously recognized interrupts.
12.4. Interrupt Latency
Interrupt response time depends on the state of the CPU when the interrupt occurs. Pending interrupts are sampled and priority decoded each system clock cycle. Therefore, the fastest possible response time is 7 system clock cycles: 1 clock cycle to detect the interrupt, 1 clock cycle to execute a single instruction, and 5 clock cycles to complete the LCALL to the ISR. If an interrupt is pending when a RETI is executed, a single instruction is executed before an LCALL is made to service the pending interrupt. Therefore, the maximum response time for an interrupt (when no other interrupt is currently being serviced or the new interrupt is of greater priority) occurs when the CPU is performing an RETI instruction followed by a DIV as the next instruction. In this case, the response time is 19 system clock cycles: 1 clock cycle to detect the interrupt, 5 clock cycles to execute the RETI, 8 clock cycles to complete the DIV instruction and 5 clock cycles to execute the LCALL to the ISR. If the CPU is executing an ISR for an interrupt with equal or higher priority, the new interrupt will not be serviced until the current ISR completes, including the RETI and following instruction.
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Table 12.1. Interrupt Summary
Interrupt Priority Pending Flag Vector Order Bit addressable? Cleared by HW? Priority Control
Interrupt Source
Enable Flag
Reset External Interrupt 0 (INT0) Timer 0 Overflow External Interrupt 1 (INT1) Timer 1 Overflow UART0 Timer 2 Overflow
0x0000 0x0003 0x000B 0x0013 0x001B 0x0023 0x002B
Top 0 1 2 3 4 5
None IE0 (TCON.1) TF0 (TCON.5) IE1 (TCON.3) TF1 (TCON.7) RI0 (SCON0.0) TI0 (SCON0.1) TF2H (TMR2CN.7) TF2L (TMR2CN.6) SPIF (SPI0CN.7) WCOL (SPI0CN.6) MODF (SPI0CN.5) RXOVRN (SPI0CN.4) SI (SMB0CN.0) ALRM (RTC0CN.2)2 AD0WINT (ADC0CN.3) AD0INT (ADC0STA.5) CF (PCA0CN.7) CCFn (PCA0CN.n) CP0FIF (CPT0CN.4) CP0RIF (CPT0CN.5) CP1FIF (CPT1CN.4) CP1RIF (CPT1CN.5) TF3H (TMR3CN.7) TF3L (TMR3CN.6) VDDOK (VDM0CN.5)1
N/A N/A Y Y Y Y Y Y Y Y Y Y N N
Always Enabled EX0 (IE.0) ET0 (IE.1) EX1 (IE.2) ET1 (IE.3) ES0 (IE.4) ET2 (IE.5)
Always Highest PX0 (IP.0) PT0 (IP.1) PX1 (IP.2) PT1 (IP.3) PS0 (IP.4) PT2 (IP.5)
SPI0
0x0033
6
Y
N
ESPI0 (IE.6) PSPI0 (IP.6) ESMB0 (EIE1.0) EARTC0 (EIE1.1) EWADC0 (EIE1.2) EADC0 (EIE1.3) EPCA0 (EIE1.4) ECP0 (EIE1.5) ECP1 (EIE1.6) ET3 (EIE1.7) EWARN (EIE2.0) EMAT (EIE2.1) ERTC0F (EIE2.2) ESPI1 (EIE2.3) PSMB0 (EIP1.0) PARTC0 (EIP1.1) PWADC0 (EIP1.2) PADC0 (EIP1.3) PPCA0 (EIP1.4) PCP0 (EIP1.5) PCP1 (EIP1.6) PT3 (EIP1.7) PWARN (EIP2.0) PMAT (EIP2.1) PFRTC0F (EIP2.2) PSPI1 (EIP2.3)
SMB0 SmaRTClock Alarm ADC0 Window Comparator ADC0 End of Conversion Programmable Counter Array Comparator0 Comparator1 Timer 3 Overflow Supply Monitor Early Warning Port Match SmaRTClock Oscillator Fail
0x003B 0x0043 0x004B 0x0053 0x005B 0x0063 0x006B 0x0073 0x007B 0x0083 0x008B
7 8 9 10 11 12 13 14 15 16 17
Y N Y Y Y N N N
N N N N N N N N
VBATOK (VDM0CN.4)1, 3
None OSCFAIL (RTC0CN.5)2 SPIF (SPI1CN.7) WCOL (SPI1CN.6) MODF (SPI1CN.5) RXOVRN (SPI1CN.4) N N
SPI1
0x0093
18
N
N
Notes: 1. Indicates a read-only interrupt pending flag. The interrupt enable may be used to prevent software from vectoring to the associated interrupt service routine. 2. Indicates a register located in an indirect memory space. 3. 8Blue text Indicates a bit only available on `F912 and `F902 devices.
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12.5. Interrupt Register Descriptions
The SFRs used to enable the interrupt sources and set their priority level are described in the following register descriptions. Refer to the data sheet section associated with a particular on-chip peripheral for information regarding valid interrupt conditions for the peripheral and the behavior of its interrupt-pending flag(s).
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SFR Definition 12.1. IE: Interrupt Enable
Bit Name Type Reset 7 EA R/W 0 6 ESPI0 R/W 0 5 ET2 R/W 0 4 ES0 R/W 0 3 ET1 R/W 0 2 EX1 R/W 0 1 ET0 R/W 0 0 EX0 R/W 0
SFR Page = All Pages; SFR Address = 0xA8; Bit-Addressable Bit Name Function 7 EA Enable All Interrupts. Globally enables/disables all interrupts. It overrides individual interrupt mask settings. 0: Disable all interrupt sources. 1: Enable each interrupt according to its individual mask setting. Enable Serial Peripheral Interface (SPI0) Interrupt. This bit sets the masking of the SPI0 interrupts. 0: Disable all SPI0 interrupts. 1: Enable interrupt requests generated by SPI0. Enable Timer 2 Interrupt. This bit sets the masking of the Timer 2 interrupt. 0: Disable Timer 2 interrupt. 1: Enable interrupt requests generated by the TF2L or TF2H flags. Enable UART0 Interrupt. This bit sets the masking of the UART0 interrupt. 0: Disable UART0 interrupt. 1: Enable UART0 interrupt. Enable Timer 1 Interrupt. This bit sets the masking of the Timer 1 interrupt. 0: Disable all Timer 1 interrupt. 1: Enable interrupt requests generated by the TF1 flag. Enable External Interrupt 1. This bit sets the masking of External Interrupt 1. 0: Disable external interrupt 1. 1: Enable interrupt requests generated by the INT1 input. Enable Timer 0 Interrupt. This bit sets the masking of the Timer 0 interrupt. 0: Disable all Timer 0 interrupt. 1: Enable interrupt requests generated by the TF0 flag. Enable External Interrupt 0. This bit sets the masking of External Interrupt 0. 0: Disable external interrupt 0. 1: Enable interrupt requests generated by the INT0 input.
6
ESPI0
5
ET2
4
ES0
3
ET1
2
EX1
1
ET0
0
EX0
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SFR Definition 12.2. IP: Interrupt Priority
Bit Name Type Reset R 1 7 6 PSPI0 R/W 0 5 PT2 R/W 0 4 PS0 R/W 0 3 PT1 R/W 0 2 PX1 R/W 0 1 PT0 R/W 0 0 PX0 R/W 0
SFR Page = 0x0; SFR Address = 0xB8; Bit-Addressable Bit Name Function 7 6 Unused PSPI0 Unused. Read = 1b, Write = don't care. Serial Peripheral Interface (SPI0) Interrupt Priority Control. This bit sets the priority of the SPI0 interrupt. 0: SPI0 interrupt set to low priority level. 1: SPI0 interrupt set to high priority level. Timer 2 Interrupt Priority Control. This bit sets the priority of the Timer 2 interrupt. 0: Timer 2 interrupt set to low priority level. 1: Timer 2 interrupt set to high priority level. UART0 Interrupt Priority Control. This bit sets the priority of the UART0 interrupt. 0: UART0 interrupt set to low priority level. 1: UART0 interrupt set to high priority level. Timer 1 Interrupt Priority Control. This bit sets the priority of the Timer 1 interrupt. 0: Timer 1 interrupt set to low priority level. 1: Timer 1 interrupt set to high priority level. External Interrupt 1 Priority Control. This bit sets the priority of the External Interrupt 1 interrupt. 0: External Interrupt 1 set to low priority level. 1: External Interrupt 1 set to high priority level. Timer 0 Interrupt Priority Control. This bit sets the priority of the Timer 0 interrupt. 0: Timer 0 interrupt set to low priority level. 1: Timer 0 interrupt set to high priority level. External Interrupt 0 Priority Control. This bit sets the priority of the External Interrupt 0 interrupt. 0: External Interrupt 0 set to low priority level. 1: External Interrupt 0 set to high priority level.
5
PT2
4
PS0
3
PT1
2
PX1
1
PT0
0
PX0
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SFR Definition 12.3. EIE1: Extended Interrupt Enable 1
Bit Name Type Reset 7 ET3 R/W 0 6 ECP1 R/W 0 5 ECP0 R/W 0 4 EPCA0 R/W 0 3 EADC0 R/W 0 2 EWADC0 R/W 0 1 ERTC0A R/W 0 0 ESMB0 R/W 0
SFR Page = All Pages; SFR Address = 0xE6 Bit Name 7 ET3
Function
Enable Timer 3 Interrupt. This bit sets the masking of the Timer 3 interrupt. 0: Disable Timer 3 interrupts. 1: Enable interrupt requests generated by the TF3L or TF3H flags. Enable Comparator1 (CP1) Interrupt. This bit sets the masking of the CP1 interrupt. 0: Disable CP1 interrupts. 1: Enable interrupt requests generated by the CP1RIF or CP1FIF flags. Enable Comparator0 (CP0) Interrupt. This bit sets the masking of the CP0 interrupt. 0: Disable CP0 interrupts. 1: Enable interrupt requests generated by the CP0RIF or CP0FIF flags. Enable Programmable Counter Array (PCA0) Interrupt. This bit sets the masking of the PCA0 interrupts. 0: Disable all PCA0 interrupts. 1: Enable interrupt requests generated by PCA0. Enable ADC0 Conversion Complete Interrupt. This bit sets the masking of the ADC0 Conversion Complete interrupt. 0: Disable ADC0 Conversion Complete interrupt. 1: Enable interrupt requests generated by the AD0INT flag.
6
ECP1
5
ECP0
4
EPCA0
3
EADC0
2
EWADC0 Enable Window Comparison ADC0 Interrupt. This bit sets the masking of ADC0 Window Comparison interrupt. 0: Disable ADC0 Window Comparison interrupt. 1: Enable interrupt requests generated by ADC0 Window Compare flag (AD0WINT). ERTC0A Enable SmaRTClock Alarm Interrupts. This bit sets the masking of the SmaRTClock Alarm interrupt. 0: Disable SmaRTClock Alarm interrupts. 1: Enable interrupt requests generated by a SmaRTClock Alarm. Enable SMBus (SMB0) Interrupt. This bit sets the masking of the SMB0 interrupt. 0: Disable all SMB0 interrupts. 1: Enable interrupt requests generated by SMB0.
1
0
ESMB0
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SFR Definition 12.4. EIP1: Extended Interrupt Priority 1
Bit Name Type Reset 7 PT3 R/W 0 6 PCP1 R/W 0 5 PCP0 R/W 0 4 PPCA0 R/W 0 3 PADC0 R/W 0 2 PWADC0 R/W 0 1 PRTC0A R/W 0 0 PSMB0 R/W 0
SFR Page = All Pages; SFR Address = 0xF6 Bit Name 7 PT3
Function
Timer 3 Interrupt Priority Control. This bit sets the priority of the Timer 3 interrupt. 0: Timer 3 interrupts set to low priority level. 1: Timer 3 interrupts set to high priority level. Comparator1 (CP1) Interrupt Priority Control. This bit sets the priority of the CP1 interrupt. 0: CP1 interrupt set to low priority level. 1: CP1 interrupt set to high priority level. Comparator0 (CP0) Interrupt Priority Control. This bit sets the priority of the CP0 interrupt. 0: CP0 interrupt set to low priority level. 1: CP0 interrupt set to high priority level. Programmable Counter Array (PCA0) Interrupt Priority Control. This bit sets the priority of the PCA0 interrupt. 0: PCA0 interrupt set to low priority level. 1: PCA0 interrupt set to high priority level. ADC0 Conversion Complete Interrupt Priority Control. This bit sets the priority of the ADC0 Conversion Complete interrupt. 0: ADC0 Conversion Complete interrupt set to low priority level. 1: ADC0 Conversion Complete interrupt set to high priority level.
6
PCP1
5
PCP0
4
PPCA0
3
PADC0
2
PWADC0 ADC0 Window Comparator Interrupt Priority Control. This bit sets the priority of the ADC0 Window interrupt. 0: ADC0 Window interrupt set to low priority level. 1: ADC0 Window interrupt set to high priority level. PRTC0A SmaRTClock Alarm Interrupt Priority Control. This bit sets the priority of the SmaRTClock Alarm interrupt. 0: SmaRTClock Alarm interrupt set to low priority level. 1: SmaRTClock Alarm interrupt set to high priority level. SMBus (SMB0) Interrupt Priority Control. This bit sets the priority of the SMB0 interrupt. 0: SMB0 interrupt set to low priority level. 1: SMB0 interrupt set to high priority level.
1
0
PSMB0
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SFR Definition 12.5. EIE2: Extended Interrupt Enable 2
Bit Name Type Reset R/W 0 R/W 0 R/W 0 R/W 0 7 6 5 4 3 ESPI1 R/W 0 2 ERTC0F R/W 0 1 EMAT R/W 0 0 EWARN R/W 0
SFR Page = All Pages;SFR Address = 0xE7 Bit Name
7:4 Unused
Function
Unused.
Read = 0000b. Write = Don't care.
3
ESPI1
Enable Serial Peripheral Interface (SPI1) Interrupt. This bit sets the masking of the SPI1 interrupts. 0: Disable all SPI1 interrupts. 1: Enable interrupt requests generated by SPI1. This bit sets the masking of the SmaRTClock Alarm interrupt. 0: Disable SmaRTClock Alarm interrupts. 1: Enable interrupt requests generated by SmaRTClock Alarm.
2
ERTC0F Enable SmaRTClock Oscillator Fail Interrupt.
1
EMAT
Enable Port Match Interrupts. This bit sets the masking of the Port Match Event interrupt. 0: Disable all Port Match interrupts. 1: Enable interrupt requests generated by a Port Match. This bit sets the masking of the Supply Monitor Early Warning interrupt. 0: Disable the Supply Monitor Early Warning interrupt. 1: Enable interrupt requests generated by the Supply Monitor(s). `F912 and `F902 devices can provide an early warning for both VBAT and the VDD/DC+ supply. All other devices only provide an early warning for the VDD/DC+ supply.
0
EWARN Enable Supply Monitor Early Warning Interrupt.
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SFR Definition 12.6. EIP2: Extended Interrupt Priority 2
Bit Name Type Reset R 0 R 0 R 0 R 0 7 6 5 4 3 PSPI1 R/W 0 2 PRTC0F R/W 0 1 PMAT R/W 0 0 PWARN R/W 0
SFR Page = All Pages; SFR Address = 0xF7 Bit Name
7:4 Unused
Function
Unused. Read = 0000b. Write = Don't care. Serial Peripheral Interface (SPI1) Interrupt Priority Control. This bit sets the priority of the SPI1 interrupt. 0: SP1 interrupt set to low priority level. 1: SPI1 interrupt set to high priority level.
3
PSPI1
2
PRTC0F SmaRTClock Oscillator Fail Interrupt Priority Control. This bit sets the priority of the SmaRTClock Alarm interrupt. 0: SmaRTClock Alarm interrupt set to low priority level. 1: SmaRTClock Alarm interrupt set to high priority level. PMAT Port Match Interrupt Priority Control. This bit sets the priority of the Port Match Event interrupt. 0: Port Match interrupt set to low priority level. 1: Port Match interrupt set to high priority level.
1
0
PWARN Supply Monitor Early Warning Interrupt Priority Control. This bit sets the priority of the VDD/DC+ Supply Monitor Early Warning interrupt. 0: Supply Monitor Early Warning interrupt set to low priority level. 1: Supply Monitor Early Warning interrupt set to high priority level.
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12.6. External Interrupts INT0 and INT1
The INT0 and INT1 external interrupt sources are configurable as active high or low, edge or level sensitive. The IN0PL (INT0 Polarity) and IN1PL (INT1 Polarity) bits in the IT01CF register select active high or active low; the IT0 and IT1 bits in TCON (Section "25.1. Timer 0 and Timer 1" on page 272) select level or edge sensitive. The table below lists the possible configurations. IT0 1 1 0 0 IN0PL 0 1 0 1 INT0 Interrupt Active low, edge sensitive Active high, edge sensitive Active low, level sensitive Active high, level sensitive IT1 1 1 0 0 IN1PL 0 1 0 1 INT1 Interrupt Active low, edge sensitive Active high, edge sensitive Active low, level sensitive Active high, level sensitive
INT0 and INT1 are assigned to Port pins as defined in the IT01CF register (see SFR Definition 12.7). Note that INT0 and INT0 Port pin assignments are independent of any Crossbar assignments. INT0 and INT1 will monitor their assigned Port pins without disturbing the peripheral that was assigned the Port pin via the Crossbar. To assign a Port pin only to INT0 and/or INT1, configure the Crossbar to skip the selected pin(s). This is accomplished by setting the associated bit in register XBR0 (see Section "21.3. Priority Crossbar Decoder" on page 209 for complete details on configuring the Crossbar). IE0 (TCON.1) and IE1 (TCON.3) serve as the interrupt-pending flags for the INT0 and INT1 external interrupts, respectively. If an INT0 or INT1 external interrupt is configured as edge-sensitive, the corresponding interrupt-pending flag is automatically cleared by the hardware when the CPU vectors to the ISR. When configured as level sensitive, the interrupt-pending flag remains logic 1 while the input is active as defined by the corresponding polarity bit (IN0PL or IN1PL); the flag remains logic 0 while the input is inactive. The external interrupt source must hold the input active until the interrupt request is recognized. It must then deactivate the interrupt request before execution of the ISR completes or another interrupt request will be generated.
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SFR Definition 12.7. IT01CF: INT0/INT1 Configuration
Bit Name Type Reset 7 IN1PL R/W 0 0 6 5 IN1SL[2:0] R/W 0 0 4 3 IN0PL R/W 0 0 2 1 IN0SL[2:0] R/W 0 1 0
SFR Page = 0x0; SFR Address = 0xE4 Bit Name 7 IN1PL INT1 Polarity. 0: INT1 input is active low. 1: INT1 input is active high.
Function
6:4
IN1SL[2:0] INT1 Port Pin Selection Bits. These bits select which Port pin is assigned to INT1. Note that this pin assignment is independent of the Crossbar; INT1 will monitor the assigned Port pin without disturbing the peripheral that has been assigned the Port pin via the Crossbar. The Crossbar will not assign the Port pin to a peripheral if it is configured to skip the selected pin. 000: Select P0.0 001: Select P0.1 010: Select P0.2 011: Select P0.3 100: Select P0.4 101: Select P0.5 110: Select P0.6 111: Select P0.7 IN0PL INT0 Polarity. 0: INT0 input is active low. 1: INT0 input is active high.
3
2:0
IN0SL[2:0] INT0 Port Pin Selection Bits. These bits select which Port pin is assigned to INT0. Note that this pin assignment is independent of the Crossbar; INT0 will monitor the assigned Port pin without disturbing the peripheral that has been assigned the Port pin via the Crossbar. The Crossbar will not assign the Port pin to a peripheral if it is configured to skip the selected pin. 000: Select P0.0 001: Select P0.1 010: Select P0.2 011: Select P0.3 100: Select P0.4 101: Select P0.5 110: Select P0.6 111: Select P0.7
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13. Flash Memory
On-chip, re-programmable Flash memory is included for program code and non-volatile data storage. The Flash memory can be programmed in-system through the C2 interface or by software using the MOVX write instruction. Once cleared to logic 0, a Flash bit must be erased to set it back to logic 1. Flash bytes would typically be erased (set to 0xFF) before being reprogrammed. The write and erase operations are automatically timed by hardware for proper execution; data polling to determine the end of the write/erase operations is not required. Code execution is stalled during Flash write/erase operations. Refer to Table 4.6 for complete Flash memory electrical characteristics.
13.1. Programming The Flash Memory
The simplest means of programming the Flash memory is through the C2 interface using programming tools provided by Silicon Laboratories or a third party vendor. This is the only means for programming a non-initialized device. For details on the C2 commands to program Flash memory, see Section "27. C2 Interface" on page 312. The Flash memory can be programmed by software using the MOVX write instruction with the address and data byte to be programmed provided as normal operands. Before programming Flash memory using MOVX, Flash programming operations must be enabled by: (1) setting the PSWE Program Store Write Enable bit (PSCTL.0) to logic 1 (this directs the MOVX writes to target Flash memory); and (2) Writing the Flash key codes in sequence to the Flash Lock register (FLKEY). The PSWE bit remains set until cleared by software. For detailed guidelines on programming Flash from firmware, please see Section "13.5. Flash Write and Erase Guidelines" on page 137. To ensure the integrity of the Flash contents, the on-chip VDD Monitor must be enabled and enabled as a reset source in any system that includes code that writes and/or erases Flash memory from software. Furthermore, there should be no delay between enabling the VDD Monitor and enabling the VDD Monitor as a reset source. Any attempt to write or erase Flash memory while the VDD Monitor is disabled, or not enabled as a reset source, will cause a Flash Error device reset.
13.1.1. Flash Lock and Key Functions
Flash writes and erases by user software are protected with a lock and key function. The Flash Lock and Key Register (FLKEY) must be written with the correct key codes, in sequence, before Flash operations may be performed. The key codes are: 0xA5, 0xF1. The timing does not matter, but the codes must be written in order. If the key codes are written out of order, or the wrong codes are written, Flash writes and erases will be disabled until the next system reset. Flash writes and erases will also be disabled if a Flash write or erase is attempted before the key codes have been written properly. The Flash lock resets after each write or erase; the key codes must be written again before a following Flash operation can be performed. The FLKEY register is detailed in SFR Definition 13.2.
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13.1.2. Flash Erase Procedure
The Flash memory is organized in 512-byte pages. The erase operation applies to an entire page (setting all bytes in the page to 0xFF). To erase an entire Flash page, perform the following steps: 1. 2. 3. 4. 5. 6. 7. 8. Save current interrupt state and disable interrupts. Set the PSEE bit (register PSCTL). Set the PSWE bit (register PSCTL). Write the first key code to FLKEY: 0xA5. Write the second key code to FLKEY: 0xF1. Using the MOVX instruction, write a data byte to any location within the page to be erased. Clear the PSWE and PSEE bits. Restore previous interrupt state.
Steps 4-6 must be repeated for each 512-byte page to be erased. Notes:
1. To maintain code compatibility with the `F93x-'F92x product family, the erase procedure should be performed on two consecutive 512-byte sections of memory at a time. This allows the same software to run on devices with 1024-byte or 512-byte Flash pages. Using this technique, devices with 1024-byte Flash pages will have each Flash page erased twice. 2. Flash security settings may prevent erasure of some Flash pages, such as the reserved area and the page containing the lock bytes. For a summary of Flash security settings and restrictions affecting Flash erase operations, please see Section "13.3. Security Options" on page 134. 3. 8-bit MOVX instructions cannot be used to erase or write to Flash memory at addresses higher than 0x00FF.
13.1.3. Flash Write Procedure
A write to Flash memory can clear bits to logic 0 but cannot set them; only an erase operation can set bits to logic 1 in Flash. A byte location to be programmed should be erased before a new value is written. The recommended procedure for writing a single byte in Flash is as follows: Save current interrupt state and disable interrupts. Ensure that the Flash byte has been erased (has a value of 0xFF). Set the PSWE bit (register PSCTL). Clear the PSEE bit (register PSCTL). Write the first key code to FLKEY: 0xA5. Write the second key code to FLKEY: 0xF1. Using the MOVX instruction, write a single data byte to the desired location within the 1024byte sector. 8. Clear the PSWE bit. 9. Restore previous interrupt state. Steps 5-7 must be repeated for each byte to be written. Notes:
1. Flash security settings may prevent writes to some areas of Flash, such as the reserved area. For a summary of Flash security settings and restrictions affecting Flash write operations, please see Section "13.3. Security Options" on page 134. 2. 8-bit MOVX instructions cannot be used to erase or write to Flash memory at addresses higher than 0x00FF.
1. 2. 3. 4. 5. 6. 7.
13.2. Non-volatile Data Storage
The Flash memory can be used for non-volatile data storage as well as program code. This allows data such as calibration coefficients to be calculated and stored at run time. Data is written using the MOVX write instruction and read using the MOVC instruction. MOVX read instructions always target XRAM. An additional 512-byte scratchpad is available for non-volatile data storage. It is accessible at addresses 0x0000 to 0x01FF when SFLE is set to 1. The scratchpad area cannot be used for code execution.
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13.3. Security Options
The CIP-51 provides security options to protect the Flash memory from inadvertent modification by software as well as to prevent the viewing of proprietary program code and constants. The Program Store Write Enable (bit PSWE in register PSCTL) and the Program Store Erase Enable (bit PSEE in register PSCTL) bits protect the Flash memory from accidental modification by software. PSWE must be explicitly set to 1 before software can modify the Flash memory; both PSWE and PSEE must be set to 1 before software can erase Flash memory. Additional security features prevent proprietary program code and data constants from being read or altered across the C2 interface. A Security Lock Byte located at the last byte of Flash user space offers protection of the Flash program memory from access (reads, writes, or erases) by unprotected code or the C2 interface. The Flash security mechanism allows the user to lock n 512-byte Flash pages, starting at page 0 (addresses 0x0000 to 0x01FF), where n is the 1s complement number represented by the Security Lock Byte. Note that the page containing the Flash Security Lock Byte is unlocked when no other Flash pages are locked (all bits of the Lock Byte are 1) and locked when any other Flash pages are locked (any bit of the Lock Byte is 0). Security Lock Byte: ones Complement: Flash pages locked: Addresses locked: 1111 1011b 0000 0100b 5 (First four Flash pages + Lock Byte Page) 0x0000 to 0x07FF (first four Flash pages) and 0x3A00 to 0x3BFF (Lock Byte Page)
16KB Flash Device (SFLE = 0)
0xFFFF
8KB Flash Device (SFLE = 0)
0xFFFF
Reserved
0x3C00 0x3BFF 0x3BFE
Lock Byte Lock Byte Page Locked when any other Flash pages are locked
Reserved
0x3A00
0x2000
Lock Byte Lock Byte Page
0x1FFF 0x1FFE 0x1E00
Unlocked Flash Pages Unlocked Flash Pages Access limit set according to the Flash security lock byte
16/8 KB Flash Device (SFLE = 1)
0x01FF
Flash memory organized in 512-byte pages
Scratchpad Area (Data Only)
0x0000 0x0000
0x0000
Figure 13.1. Flash Program Memory Map (16 kB and 8 kB devices)
The level of Flash security depends on the Flash access method. The three Flash access methods that can be restricted are reads, writes, and erases from the C2 debug interface, user firmware executing on unlocked pages, and user firmware executing on locked pages. Table 13.1 summarizes the Flash security features of the C8051F91x-C8051F90x devices.
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Table 13.1. Flash Security Summary
Action C2 Debug Interface Permitted User Firmware executing from: an unlocked page Permitted a locked page Permitted Permitted Permitted Permitted Permitted Permitted FEDR FEDR FEDR FEDR FEDR
Read, Write or Erase unlocked pages (except page with Lock Byte) Read, Write or Erase locked pages (except page with Lock Byte) Read or Write page containing Lock Byte (if no pages are locked) Read or Write page containing Lock Byte (if any page is locked) Read contents of Lock Byte (if no pages are locked) Read contents of Lock Byte (if any page is locked) Erase page containing Lock Byte (if no pages are locked) Erase page containing Lock Byte - Unlock all pages (if any page is locked) Lock additional pages (change 1s to 0s in the Lock Byte) Unlock individual pages (change 0s to 1s in the Lock Byte) Read, Write or Erase Reserved Area
Not Permitted FEDR Permitted Permitted
Not Permitted FEDR Permitted Permitted
Not Permitted FEDR Permitted FEDR
Only by C2DE FEDR Not Permitted FEDR Not Permitted FEDR Not Permitted FEDR
C2DE--C2 Device Erase (Erases all Flash pages including the page containing the Lock Byte) FEDR--Not permitted; Causes Flash Error Device Reset (FERROR bit in RSTSRC is 1 after reset) * * * * * * All prohibited operations that are performed via the C2 interface are ignored (do not cause device reset). Locking any Flash page also locks the page containing the Lock Byte. Once written to, the Lock Byte cannot be modified except by performing a C2 Device Erase. If user code writes to the Lock Byte, the Lock does not take effect until the next device reset. The scratchpad is locked when all other Flash pages are locked. The scratchpad is erased when a Flash Device Erase command is performed.
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13.4. Determining the Device Part Number at Run Time
In many applications, user software may need to determine the MCU part number at run time in order to determine the hardware capabilities. The part number can be determined by reading the value of the Flash byte at address 0x3FFE. The value of the Flash byte at address 0x3FFE can be decoded as follows: 0xD0--C8051F901 0xD1--C8051F902 0xD2--C8051F911 0xD3--C8051F912
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13.5. Flash Write and Erase Guidelines
Any system which contains routines which write or erase Flash memory from software involves some risk that the write or erase routines will execute unintentionally if the CPU is operating outside its specified operating range of VDD, system clock frequency, or temperature. This accidental execution of Flash modifying code can result in alteration of Flash memory contents causing a system failure that is only recoverable by re-Flashing the code in the device. To help prevent the accidental modification of Flash by firmware, the VDD Monitor must be enabled and enabled as a reset source on C8051F91x-C8051F90x devices for the Flash to be successfully modified. If either the VDD Monitor or the VDD Monitor reset source is not enabled, a Flash Error Device Reset will be generated when the firmware attempts to modify the Flash. The following guidelines are recommended for any system that contains routines which write or erase Flash from code.
13.5.1. VDD Maintenance and the VDD Monitor
1. If the system power supply is subject to voltage or current "spikes," add sufficient transient protection devices to the power supply to ensure that the supply voltages listed in the Absolute Maximum Ratings table are not exceeded. 2. Make certain that the minimum VDD rise time specification of 1 ms is met. If the system cannot meet this rise time specification, then add an external VDD brownout circuit to the RST pin of the device that holds the device in reset until VDD reaches the minimum device operating voltage and re-asserts RST if VDD drops below the minimum device operating voltage. 3. Keep the on-chip VDD Monitor enabled and enable the VDD Monitor as a reset source as early in code as possible. This should be the first set of instructions executed after the Reset Vector. For C-based systems, this will involve modifying the startup code added by the C compiler. See your compiler documentation for more details. Make certain that there are no delays in software between enabling the VDD Monitor and enabling the VDD Monitor as a reset source. Code examples showing this can be found in "AN201: Writing to Flash from Firmware," available from the Silicon Laboratories website. Note: On C8051F91x-C8051F90x devices, both the VDD Monitor and the VDD Monitor reset source must be enabled to write or erase Flash without generating a Flash Error Device Reset. Note: On C8051F91x-C8051F90x devices, both the VDD Monitor and the VDD Monitor reset source are enabled by hardware after a power-on reset. 4. As an added precaution, explicitly enable the VDD Monitor and enable the VDD Monitor as a reset source inside the functions that write and erase Flash memory. The VDD Monitor enable instructions should be placed just after the instruction to set PSWE to a 1, but before the Flash write or erase operation instruction. 5. Make certain that all writes to the RSTSRC (Reset Sources) register use direct assignment operators and explicitly DO NOT use the bit-wise operators (such as AND or OR). For example, "RSTSRC = 0x02" is correct, but "RSTSRC |= 0x02" is incorrect. 6. Make certain that all writes to the RSTSRC register explicitly set the PORSF bit to a 1. Areas to check are initialization code which enables other reset sources, such as the Missing Clock Detector or Comparator, for example, and instructions which force a Software Reset. A global search on "RSTSRC" can quickly verify this.
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13.5.2. PSWE Maintenance
7. Reduce the number of places in code where the PSWE bit (b0 in PSCTL) is set to a 1. There should be exactly one routine in code that sets PSWE to a 1 to write Flash bytes and one routine in code that sets both PSWE and PSEE both to a 1 to erase Flash pages. 8. Minimize the number of variable accesses while PSWE is set to a 1. Handle pointer address updates and loop maintenance outside the "PSWE = 1;... PSWE = 0;" area. Code examples showing this can be found in AN201, "Writing to Flash from Firmware", available from the Silicon Laboratories web site. 9. Disable interrupts prior to setting PSWE to a 1 and leave them disabled until after PSWE has been reset to 0. Any interrupts posted during the Flash write or erase operation will be serviced in priority order after the Flash operation has been completed and interrupts have been re-enabled by software. 10. Make certain that the Flash write and erase pointer variables are not located in XRAM. See your compiler documentation for instructions regarding how to explicitly locate variables in different memory areas. 11. Add address bounds checking to the routines that write or erase Flash memory to ensure that a routine called with an illegal address does not result in modification of the Flash.
13.5.3. System Clock
12. If operating from an external crystal, be advised that crystal performance is susceptible to electrical interference and is sensitive to layout and to changes in temperature. If the system is operating in an electrically noisy environment, use the internal oscillator or use an external CMOS clock. 13. If operating from the external oscillator, switch to the internal oscillator during Flash write or erase operations. The external oscillator can continue to run, and the CPU can switch back to the external oscillator after the Flash operation has completed. Additional Flash recommendations and example code can be found in "AN201: Writing to Flash from Firmware", available from the Silicon Laboratories web site.
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13.6. Minimizing Flash Read Current
The Flash memory in the C8051F91x-C8051F90x devices is responsible for a substantial portion of the total digital supply current when the device is executing code. Below are suggestions to minimize Flash read current. 1. Use idle, suspend, or sleep modes while waiting for an interrupt, rather than polling the interrupt flag. Idle Mode is particularly well-suited for use in implementing short pauses, since the wake-up time is no more than three system clock cycles. See the Power Management chapter for details on the various low-power operating modes. 2. C8051F91x-C8051F90x devices have a one-shot timer that saves power when operating at system clock frequencies of 14 MHz or less. The one-shot timer generates a minimum-duration enable signal for the Flash sense amps on each clock cycle in which the Flash memory is accessed. This allows the Flash to remain in a low power state for the remainder of the long clock cycle. At clock frequencies above 14 MHz, the system clock cycle becomes short enough that the one-shot timer no longer provides a power benefit. Disabling the one-shot timer at higher frequencies reduces power consumption. The one-shot is enabled by default, and it can be disabled (bypassed) by setting the BYPASS bit (FLSCL.6) to logic 1. To re-enable the one-shot, clear the BYPASS bit to logic 0. 3. Flash read current depends on the number of address lines that toggle between sequential Flash read operations. In most cases, the difference in power is relatively small (on the order of 5%). The Flash memory is organized in rows of 64 bytes. A substantial current increase can be detected when the read address jumps from one row in the Flash memory to another. Consider a 3-cycle loop (e.g., SJMP $, or while(1);) which straddles a Flash row boundary. The Flash address jumps from one row to another on two of every three clock cycles. This can result in a current increase of up 30% when compared to the same 3-cycle loop contained entirely within a single row. To minimize the power consumption of small loops, it is best to locate them within a single row, if possible. To check if a loop is contained within a Flash row, divide the starting address of the first instruction in the loop by 64. If the remainder (result of modulo operation) plus the length of the loop is less than 63, then the loop fits inside a single Flash row. Otherwise, the loop will be straddling two adjacent Flash rows. If a loop executes in 20 or more clock cycles, then the transitions from one row to another will occur on relatively few clock cycles, and any resulting increase in operating current will be negligible. To write software that is compatible with all devices in the `F93x-'F92x and `F91x-'F90x product families, the Flash row size should be considered 64 bytes.
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SFR Definition 13.1. PSCTL: Program Store R/W Control
Bit Name Type Reset R 0 R 0 R 0 R 0 R 0 7 6 5 4 3 2 SFLE R/W 0 1 PSEE R/W 0 0 PSWE R/W 0
SFR Page =0x0; SFR Address = 0x8F Bit Name 7:3 2 Unused SFLE Unused. Read = 00000b, Write = don't care.
Function
Scratchpad Flash Memory Access Enable. When this bit is set, Flash MOVC reads and MOVX writes from user software are directed to the Scratchpad Flash sector. Flash accesses outside the address range 0x0000-0x01FF should not be attempted and may yield undefined results when SFLE is set to 1. 0: Flash access from user software directed to the Program/Data Flash sector. 1: Flash access from user software directed to the Scratchpad Sector.
1
PSEE
Program Store Erase Enable. Setting this bit (in combination with PSWE) allows an entire page of Flash program memory to be erased. If this bit is logic 1 and Flash writes are enabled (PSWE is logic 1), a write to Flash memory using the MOVX instruction will erase the entire page that contains the location addressed by the MOVX instruction. The value of the data byte written does not matter. 0: Flash program memory erasure disabled. 1: Flash program memory erasure enabled.
0
PSWE
Program Store Write Enable. Setting this bit allows writing a byte of data to the Flash program memory using the MOVX write instruction. The Flash location should be erased before writing data. 0: Writes to Flash program memory disabled. 1: Writes to Flash program memory enabled; the MOVX write instruction targets Flash memory.
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SFR Definition 13.2. FLKEY: Flash Lock and Key
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
FLKEY[7:0] R/W 0 Function 0 0 0
SFR Page = 0x0; SFR Address = 0xB6 Bit Name 7:0 FLKEY[7:0] Flash Lock and Key Register.
Write: This register provides a lock and key function for Flash erasures and writes. Flash writes and erases are enabled by writing 0xA5 followed by 0xF1 to the FLKEY register. Flash writes and erases are automatically disabled after the next write or erase is complete. If any writes to FLKEY are performed incorrectly, or if a Flash write or erase operation is attempted while these operations are disabled, the Flash will be permanently locked from writes or erasures until the next device reset. If an application never writes to Flash, it can intentionally lock the Flash by writing a non-0xA5 value to FLKEY from software. Read: When read, bits 1-0 indicate the current Flash lock state. 00: Flash is write/erase locked. 01: The first key code has been written (0xA5). 10: Flash is unlocked (writes/erases allowed). 11: Flash writes/erases disabled until the next reset.
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SFR Definition 13.3. FLSCL: Flash Scale
Bit Name Type Reset R 0 7 6 BYPASS R/W 0 R 0 R 0 R 0 Function R 0 R 0 R 0 5 4 3 2 1 0
SFR Page = 0x0; SFR Address = 0xB6 Bit Name 7 6 Reserved BYPASS Reserved. Always Write to 0.
Flash Read Timing One-Shot Bypass. 0: The one-shot determines the Flash read time. This setting should be used for operating frequencies less than 10 MHz. 1: The system clock determines the Flash read time. This setting should be used for frequencies greater than 10 MHz.
5:0
Reserved
Reserved. Always Write to 000000.
Note: Operations which clear the BYPASS bit do not need to be immediately followed by a benign 3-byte instruction on C8051F912/11/02/01 devices. For code compatibility with C8051F930/31/20/21 devices, a benign 3-byte instruction whose third byte is a don't care should follow the clear operation. See the C8051F93x-C8051F92x data sheet for more details.
SFR Definition 13.4. FLWR: Flash Write Only
Bit Name Type Reset 0 0 0 0 7 6 5 4 FLWR[7:0] W 0 Function 0 0 0 3 2 1 0
SFR Page = 0x0; SFR Address = 0xE5 Bit Name 7:0 FLWR[7:0] Flash Write Only.
All writes to this register have no effect on system operation.
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14. Power Management
C8051F91x-C8051F90x devices support 5 power modes: Normal, Idle, Stop, Suspend, and Sleep. The power management unit (PMU0) allows the device to enter and wake-up from the available power modes. A brief description of each power mode is provided in Table 14.1. Detailed descriptions of each mode can be found in the following sections.
Table 14.1. Power Modes
Power Mode Normal Idle Stop Description Device fully functional All peripherals fully functional. Very easy to wake up. Legacy 8051 low power mode. A reset is required to wake up. Similar to Stop Mode, but very fast wake-up time and code resumes execution at the next instruction. Ultra Low Power and flexible wake-up sources. Code resumes execution at the next instruction. Comparator0 only functional in two-cell mode. Wake-Up Sources N/A Any Interrupt. Any Reset. Power Savings Excellent MIPS/mW Good No Code Execution Good No Code Execution Precision Oscillator Disabled Very Good No Code Execution All Internal Oscillators Disabled System Clock Gated Excellent Power Supply Gated All Oscillators except SmaRTClock Disabled
Suspend
SmaRTClock, Port Match, Comparator0, RST pin. SmaRTClock, Port Match, Comparator0, RST pin.
Sleep
In battery powered systems, the system should spend as much time as possible in sleep mode in order to preserve battery life. When a task with a fixed number of clock cycles needs to be performed, the device should switch to normal mode, finish the task as quickly as possible, and return to sleep mode. Idle mode and suspend modes provide a very fast wake-up time; however, the power savings in these modes will not be as much as in sleep mode. Stop mode is included for legacy reasons; the system will be more power efficient and easier to wake up when idle, suspend, or sleep mode are used. Although switching power modes is an integral part of power management, enabling/disabling individual peripherals as needed will help lower power consumption in all power modes. Each analog peripheral can be disabled when not in use or placed in a low power mode. Digital peripherals such as timers or serial busses draw little power whenever they are not in use. Digital peripherals draw no power in Sleep Mode.
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14.1. Normal Mode
The MCU is fully functional in normal mode. Figure 14.1 shows the on-chip power distribution to various peripherals. There are three supply voltages powering various sections of the chip: VBAT, VDD/DC+, and the 1.8 V internal core supply. VREG0, PMU0 and the SmaRTClock are always powered directly from the VBAT pin. All analog peripherals are directly powered from the VDD/DC+ pin, which is an output in one-cell mode and an input in two-cell mode. All digital peripherals and the CIP-51 core are powered from the 1.8 V internal core supply. The RAM is also powered from the core supply in Normal mode.
VBAT
One-cell: 0.9 to 3.6 V (F912/02 devices only) One-cell: 0.9 to 1.8 V VDD/DC+ One-cell or Two-cell: 1.8 to 3.6 V Two-cell: 1.8 to 3.6 V 1.9 V typical Note: VDD/DC+ must be > VBAT GPIO
DC0
Analog Peripherals
One-Cell Active/ Idle/Stop/Suspend One-Cell Sleep VREG0
VREF A M U X 10-bit 300 ksps ADC TEMP SENSOR IREF0
+ -
+ VOLTAGE COMPARATORS
Sleep PMU0 SmaRTClock
Active/Idle/ Stop/Suspend 1.8 V
Digital Peripherals
UART Flash CIP-51 Core SPI Timers SMBus
RAM
Figure 14.1. C8051F91x-C8051F90x Power Distribution
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14.2. Idle Mode
Setting the Idle Mode Select bit (PCON.0) causes the CIP-51 to halt the CPU and enter Idle mode as soon as the instruction that sets the bit completes execution. All internal registers and memory maintain their original data. All analog and digital peripherals can remain active during Idle mode.
Note: To ensure the MCU enters a low power state upon entry into Idle Mode, the one-shot circuit should be enabled by clearing the BYPASS bit (FLSCL.6).
Idle mode is terminated when an enabled interrupt is asserted or a reset occurs. The assertion of an enabled interrupt will cause the Idle Mode Selection bit (PCON.0) to be cleared and the CPU to resume operation. The pending interrupt will be serviced and the next instruction to be executed after the return from interrupt (RETI) will be the instruction immediately following the one that set the Idle Mode Select bit. If Idle mode is terminated by an internal or external reset, the CIP-51 performs a normal reset sequence and begins program execution at address 0x0000. If enabled, the Watchdog Timer (WDT) will eventually cause an internal watchdog reset and thereby terminate the Idle mode. This feature protects the system from an unintended permanent shutdown in the event of an inadvertent write to the PCON register. If this behavior is not desired, the WDT may be disabled by software prior to entering the idle mode if the WDT was initially configured to allow this operation. This provides the opportunity for additional power savings, allowing the system to remain in the idle mode indefinitely, waiting for an external stimulus to wake up the system. Refer to Section "18.6. PCA Watchdog Timer Reset" on page 176 for more information on the use and configuration of the WDT.
14.3. Stop Mode
Setting the Stop Mode Select bit (PCON.1) causes the CIP-51 to enter stop mode as soon as the instruction that sets the bit completes execution. In stop mode the precision internal oscillator and CPU are stopped; the state of the low power oscillator and the external oscillator circuit is not affected. Each analog peripheral (including the external oscillator circuit) may be shut down individually prior to entering stop mode. Stop mode can only be terminated by an internal or external reset. On reset, the CIP-51 performs the normal reset sequence and begins program execution at address 0x0000. If enabled, the Missing Clock Detector will cause an internal reset and thereby terminate the Stop mode. The Missing Clock Detector should be disabled if the CPU is to be put to in STOP mode for longer than the MCD timeout. Stop mode is a legacy 8051 power mode; it will not result in optimal power savings. Sleep or suspend mode will provide more power savings if the MCU needs to be inactive for a long period of time.
Note: To ensure the MCU enters a low power state upon entry into Stop Mode, the one-shot circuit should be enabled by clearing the BYPASS bit (FLSCL.6).
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14.4. Suspend Mode
Setting the Suspend Mode Select bit (PMU0CF.6) causes the system clock to be gated off and all internal oscillators disabled. The system clock source must be set to the low power internal oscillator or the precision oscillator prior to entering suspend mode. All digital logic (timers, communication peripherals, interrupts, CPU, etc.) stops functioning until one of the enabled wake-up sources occurs. The following wake-up sources can be configured to wake the device from suspend mode:
SmaRTClock Oscillator Fail SmaRTClock Alarm Port Match Event Comparator0 Rising Edge
Note: Upon wake-up from suspend mode, PMU0 requires two system clocks in order to update the PMU0CF wakeup flags. All flags will read back a value of '0' during the first two system clocks following a wake-up from suspend mode.
In addition, a noise glitch on RST that is not long enough to reset the device will cause the device to exit suspend. In order for the MCU to respond to the pin reset event, software must not place the device back into suspend mode for a period of 15 s. The PMU0CF register may be checked to determine if the wakeup was due to a falling edge on the /RST pin. If the wake-up source is not due to a falling edge on RST, there is no time restriction on how soon software may place the device back into suspend mode. A 4.7 kW pullup resistor to VDD/DC+ is recommend for RST to prevent noise glitches from waking the device.
14.5. Sleep Mode
Setting the Sleep Mode Select bit (PMU0CF.6) turns off the internal 1.8 V regulator (VREG0) and switches the power supply of all on-chip RAM to the VBAT pin (see Figure 14.1). Power to most digital logic on the chip is disconnected; only PMU0 and the SmaRTClock remain powered. Analog peripherals remain powered in two-cell mode and lose their supply in one-cell mode because the dc-dc converter is disabled. In two-cell mode, only the Comparators remain functional when the device enters sleep mode. All other analog peripherals (ADC0, IREF0, External Oscillator, etc.) should be disabled prior to entering sleep mode. The system clock source must be set to the low power internal oscillator or the precision oscillator prior to entering sleep mode.
Note: When exiting sleep mode, 4 NOP instructions should be located immediately after the write to PMU0CF that placed the device in sleep mode. Note: If the average active time (between successive entries into Sleep Mode) is less than 1 ms, peripherals that may cause a wake-up from Sleep Mode (SmaRTClock, Port Match, and Comparator0) or are enabled or configured in a way which may cause the wake-up flag to be set should be selected as wake-up sources. If these peripherals are not selected as wake-up sources, then it is recommended to bypass the Flash one-shot (FLSCL.6=1) before entering into Sleep Mode.
GPIO pins configured as digital outputs will retain their output state during sleep mode. In two-cell mode, they will maintain the same current drive capability in sleep mode as they have in normal mode. In one-cell mode, the VDD/DC+ supply will drop to the level of VBAT, which will reduce the output high-voltage level and the source and sink current drive capability. GPIO pins configured as digital inputs can be used during sleep mode as wakeup sources using the port match feature. In two-cell mode, they will maintain the same input level specs in sleep mode as they have in normal mode. In one-cell mode, the VDD supply will drop to the level of VBAT, which will lower the switching threshold and increase the propagation delay. C8051F912 and C8051F902 devices support a wakeup request for external devices. Upon exit from sleep mode, the wake-up request signal is driven high, allowing other devices in the system to wake up from their low power modes. An example of a system that may benefit from this function is one that uses a highpower dc-dc converter (>65 mW of output power). The dc-dc converter may be disabled when the system is asleep, and can be awoken by the wake-up request signal from the MCU. The wakeup request signal is high when the MCU is awake and low when the MCU is asleep.
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Note: By default, the VDD/DC+ supply is connected to VBAT upon entry into Sleep Mode (one-cell mode). If the VDDSLP bit (DC0CF.1) is set to logic 1, the VDD/DC+ supply will float in Sleep Mode. This allows the decoupling capacitance on the VDD/DC+ supply to maintain the supply rail until the capacitors are discharged. For relatively short sleep intervals, this can result in substantial power savings because the decoupling capacitance is not continuously charged and discharged.
RAM and SFR register contents are preserved in sleep mode as long as the voltage on VBAT does not fall below VPOR. The PC counter and all other volatile state information is preserved allowing the device to resume code execution upon waking up from Sleep mode. The following wake-up sources can be configured to wake the device from sleep mode:
SmaRTClock Oscillator Fail SmaRTClock Alarm Port Match Event Comparator0 Rising Edge. The Comparator0 Rising Edge wakeup is only valid in two-cell mode. The comparator requires a supply voltage of at least 1.8 V to operate properly. On `F912 and `F902 devices, the VBAT supply monitor can be disabled to save power by writing 1 to the MONDIS (PMU0MD.5) bit. When the VBAT supply monitor is disabled, all reset sources will trigger a full POR and will re-enable the VBAT supply monitor. In addition, any falling edge on RST (due to a pin reset or a noise glitch) will cause the device to exit sleep mode. In order for the MCU to respond to the pin reset event, software must not place the device back into sleep mode for a period of 15 s. The PMU0CF register may be checked to determine if the wake-up was due to a falling edge on the RST pin. If the wake-up source is not due to a falling edge on RST, there is no time restriction on how soon software may place the device back into sleep mode. A 4.7 k pullup resistor to VDD/DC+ is recommend for RST to prevent noise glitches from waking the device.
14.6. Configuring Wakeup Sources
Before placing the device in a low power mode, one or more wakeup sources should be enabled so that the device does not remain in the low power mode indefinitely. For Idle Mode, this includes enabling any interrupt. For Stop Mode, this includes enabling any reset source or relying on the RST pin to reset the device. Wake-up sources for suspend and sleep modes are configured through the PMU0CF register. Wake-up sources are enabled by writing 1 to the corresponding wake-up source enable bit. Wake-up sources must be re-enabled each time the device is placed in suspend or sleep mode, in the same write that places the device in the low power mode. The reset pin is always enabled as a wake-up source. On the falling edge of RST, the device will be awaken from sleep mode. The device must remain awake for more than 15 s in order for the reset to take place.
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14.7. Determining the Event that Caused the Last Wakeup
When waking from idle mode, the CPU will vector to the interrupt which caused it to wake up. When waking from stop mode, the RSTSRC register may be read to determine the cause of the last reset. Upon exit from suspend or sleep mode, the wake-up flags in the PMU0CF register can be read to determine the event which caused the device to wake up. After waking up, the wake-up flags will continue to be updated if any of the wake-up events occur. Wake-up flags are always updated, even if they are not enabled as wake-up sources. All wake-up flags enabled as wake-up sources in PMU0CF must be cleared before the device can enter suspend or sleep mode. After clearing the wake-up flags, each of the enabled wake-up events should be checked in the individual peripherals to ensure that a wake-up event did not occur while the wake-up flags were being cleared.
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SFR Definition 14.1. PMU0CF: Power Management Unit Configuration1,2
Bit Name Type Reset 7 SLEEP W 0 6 SUSPEND W 0 5 CLEAR W 0 4 RSTWK R Varies 3 RTCFWK R/W Varies 2 RTCAWK R/W Varies 1 PMATWK R/W Varies 0 CPT0WK R/W Varies
SFR Page = 0x0; SFR Address = 0xB5 Bit Name Description 7 6 5 4 SLEEP SUSPEND CLEAR RSTWK Sleep Mode Select Suspend Mode Select Wake-up Flag Clear Reset Pin Wake-up Flag
Write Writing 1 places the device in Sleep Mode. Writing 1 places the device in Suspend Mode. Writing 1 clears all wakeup flags. N/A N/A N/A N/A
Read
3
RTCFWK
SmaRTClock Oscillator Fail Wake-up Source Enable and Flag SmaRTClock Alarm Wake-up Source Enable and Flag Port Match Wake-up Source Enable and Flag
2
RTCAWK
1
PMATWK
0
CPT0WK
Comparator0 Wake-up Source Enable and Flag
0: Disable wake-up on SmaRTClock Osc. Fail. 1: Enable wake-up on SmaRTClock Osc. Fail. 0: Disable wake-up on SmaRTClock Alarm. 1: Enable wake-up on SmaRTClock Alarm. 0: Disable wake-up on Port Match Event. 1: Enable wake-up on Port Match Event. 0: Disable wake-up on Comparator0 rising edge. 1: Enable wake-up on Comparator0 rising edge.
Set to 1 if a falling edge has been detected on RST. Set to 1 if the SmaRTClock Oscillator has failed.
Set to 1 if a SmaRTClock Alarm has occurred.
Set to 1 if a Port Match Event has occurred.
Set to 1 if Comparator0 rising edge has occurred.
Notes: 1. Read-modify-write operations (ORL, ANL, etc.) should not be used on this register. Wake-up sources must be re-enabled each time the SLEEP or SUSPEND bits are written to 1. 2. The Low Power Internal Oscillator cannot be disabled and the MCU cannot be placed in Suspend or Sleep Mode if any wake-up flags are set to 1. Software should clear all wake-up sources after each reset and after each wake-up from Suspend or Sleep Modes. 3. PMU0 requires two system clocks to update the wake-up source flags after waking from Suspend mode. The wake-up source flags will read `0' during the first two system clocks following the wake from Suspend mode.
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SFR Definition 14.2. PMU0MD: Power Management Unit Mode
Bit 7 6 WAKEOE R/W 0 5 MONDIS R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 4 3 2 1 0
Name RTCOE Type Reset R/W 0
SFR Page = 0xF; SFR Address = 0xB5 Bit Name 7 RTCOE
Function
Buffered SmaRTClock Output Enable. Enables the buffered SmaRTClock oscillator output on P0.2. Only available on `F912 and `F902 devices. 0: Buffered SmaRTClock output is not enabled. 1: Buffered SmaRTClock output is enabled.
6
WAKEOE
Wakeup Request Output Enable. Enables the Sleep Mode wake-up request signal on P0.3. Only available on `F912 and `F902 devices. 0: Wake-up request signal is not enabled. 1: Wake-up request signal is enabled.
5
MONDIS
VBAT Supply Monitor Disable. Writing a 1 to this bit disables the VBAT supply monitor. Writing a 0 to this bit when the VBAT supply monitor is disabled will trigger a power-on reset. Only available on `F912 and `F902 devices.
4:0
Unused
Unused. Read = 00000b. Write = Don't Care.
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SFR Definition 14.3. PCON: Power Management Control Register
Bit Name Type Reset 0 0 0 7 6 5 GF[5:0] R/W 0 0 0 4 3 2 1 STOP W 0 0 IDLE W 0
SFR Page = All Pages; SFR Address = 0x87 Bit Name Description 7:2 1 0 GF[5:0] STOP IDLE General Purpose Flags Stop Mode Select Idle Mode Select
Write Sets the logic value. Writing 1 places the device in Stop Mode. Writing 1 places the device in Idle Mode. N/A N/A
Read Returns the logic value.
14.8. Power Management Specifications
See Table 4.5 on page 53 for detailed Power Management Specifications.
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15. Cyclic Redundancy Check Unit (CRC0)
C8051F91x-C8051F90x devices include a cyclic redundancy check unit (CRC0) that can perform a CRC using a 16-bit or 32-bit polynomial. CRC0 accepts a stream of 8-bit data written to the CRC0IN register. CRC0 posts the 16-bit or 32-bit result to an internal register. The internal result register may be accessed indirectly using the CRC0PNT bits and CRC0DAT register, as shown in Figure 15.1. CRC0 also has a bit reverse register for quick data manipulation.
CRC0IN
8
8
Automatic CRC Controller
Flash Memory
CRC0CN
CRC0SEL CRC0INIT CRC0VAL CRC0PNT1 CRC0PNT0 CRC0FLIP Write
CRC0AUTO CRC Engine 32 RESULT 8 8 8 4 to 1 MUX 8 8 CRC0CNT
CRC0DAT
CRC0FLIP Read
Figure 15.1. CRC0 Block Diagram
15.1. CRC Algorithm
The C8051F91x-C8051F90x CRC unit generates a CRC result equivalent to the following algorithm: 1. XOR the input with the most-significant bits of the current CRC result. If this is the first iteration of the CRC unit, the current CRC result will be the set initial value (0x00000000 or 0xFFFFFFFF). 2a. If the MSB of the CRC result is set, shift the CRC result and XOR the result with the selected polynomial. 2b. If the MSB of the CRC result is not set, shift the CRC result. Repeat Steps 2a/2b for the number of input bits (8). The algorithm is also described in the following example. The 16-bit C8051F91x-C8051F90x CRC algorithm can be described by the following code:
unsigned short UpdateCRC (unsigned short CRC_acc, unsigned char CRC_input) { unsigned char i; // loop counter #define POLY 0x1021 // Create the CRC "dividend" for polynomial arithmetic (binary arithmetic
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// with no carries) CRC_acc = CRC_acc ^ (CRC_input << 8); // "Divide" the poly into the dividend using CRC XOR subtraction // CRC_acc holds the "remainder" of each divide // // Only complete this division for 8 bits since input is 1 byte for (i = 0; i < 8; i++) { // Check if the MSB is set (if MSB is 1, then the POLY can "divide" // into the "dividend") if ((CRC_acc & 0x8000) == 0x8000) { // if so, shift the CRC value, and XOR "subtract" the poly CRC_acc = CRC_acc << 1; CRC_acc ^= POLY; } else { // if not, just shift the CRC value CRC_acc = CRC_acc << 1; } } // Return the final remainder (CRC value) return CRC_acc; }
Table 15.1 lists several input values and the associated outputs using the 16-bit C8051F91x-C8051F90x CRC algorithm:
Table 15.1. Example 16-bit CRC Outputs
Input 0x63 0x8C 0x7D 0xAA, 0xBB, 0xCC 0x00, 0x00, 0xAA, 0xBB, 0xCC Output 0xBD35 0xB1F4 0x4ECA 0x6CF6 0xB166
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15.2. Preparing for a CRC Calculation
To prepare CRC0 for a CRC calculation, software should select the desired polynomial and set the initial value of the result. Two polynomials are available: 0x1021 (16-bit) and 0x04C11DB7 (32-bit). The CRC0 result may be initialized to one of two values: 0x00000000 or 0xFFFFFFFF. The following steps can be used to initialize CRC0. 1. Select a polynomial (Set CRC0SEL to 0 for 32-bit or 1 for 16-bit). 2. Select the initial result value (Set CRC0VAL to 0 for 0x00000000 or 1 for 0xFFFFFFFF). 3. Set the result to its initial value (Write 1 to CRC0INIT).
15.3. Performing a CRC Calculation
Once CRC0 is initialized, the input data stream is sequentially written to CRC0IN, one byte at a time. The CRC0 result is automatically updated after each byte is written. The CRC engine may also be configured to automatically perform a CRC on one or more Flash sectors. The following steps can be used to automatically perform a CRC on Flash memory. 1. 2. 3. 4. Prepare CRC0 for a CRC calculation as shown above. Write the index of the starting page to CRC0AUTO. Set the AUTOEN bit in CRC0AUTO. Write the number of Flash sectors to perform in the CRC calculation to CRC0CNT. Note: Each Flash sector is 512 bytes on `F91x and `F90x devices. 5. Write any value to CRC0CN (or OR its contents with 0x00) to initiate the CRC calculation. The CPU will not execute code any additional code until the CRC operation completes. See the note in SFR Definition 15.1. CRC0CN: CRC0 Control for more information on how to properly initiate a CRC calculation. 6. Clear the AUTOEN bit in CRC0AUTO. 7. Read the CRC result using the procedure below.
15.4. Accessing the CRC0 Result
The internal CRC0 result is 32-bits (CRC0SEL = 0b) or 16-bits (CRC0SEL = 1b). The CRC0PNT bits select the byte that is targeted by read and write operations on CRC0DAT and increment after each read or write. The calculation result will remain in the internal CR0 result register until it is set, overwritten, or additional data is written to CRC0IN.
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SFR Definition 15.1. CRC0CN: CRC0 Control
Bit Name Type Reset R/W 0 R/W 0 R/W 0 7 6 5 4 3 2 1 0
CRC0SEL CRC0INIT CRC0VAL R/W 0 R/W 0 R/W 0
CRC0PNT[1:0] R/W 0 0
SFR Page = 0xF; SFR Address = 0x92 Bit Name 7:5 4 Unused CRC0SEL Unused. Read = 000b; Write = Don't Care. CRC0 Polynomial Select Bit.
Function
This bit selects the CRC0 polynomial and result length (32-bit or 16-bit). 0: CRC0 uses the 32-bit polynomial 0x04C11DB7 for calculating the CRC result. 1: CRC0 uses the 16-bit polynomial 0x1021 for calculating the CRC result. 3 2 CRC0INIT CRC0VAL CRC0 Result Initialization Bit. Writing a 1 to this bit initializes the entire CRC result based on CRC0VAL. CRC0 Set Value Initialization Bit. This bit selects the set value of the CRC result. 0: CRC result is set to 0x00000000 on write of 1 to CRC0INIT. 1: CRC result is set to 0xFFFFFFFF on write of 1 to CRC0INIT. 1:0 CRC0PNT[1:0] CRC0 Result Pointer. Specifies the byte of the CRC result to be read/written on the next access to CRC0DAT. The value of these bits will auto-increment upon each read or write. For CRC0SEL = 0: 00: CRC0DAT accesses bits 7-0 of the 32-bit CRC result. 01: CRC0DAT accesses bits 15-8 of the 32-bit CRC result. 10: CRC0DAT accesses bits 23-16 of the 32-bit CRC result. 11: CRC0DAT accesses bits 31-24 of the 32-bit CRC result. For CRC0SEL = 1: 00: CRC0DAT accesses bits 7-0 of the 16-bit CRC result. 01: CRC0DAT accesses bits 15-8 of the 16-bit CRC result. 10: CRC0DAT accesses bits 7-0 of the 16-bit CRC result. 11: CRC0DAT accesses bits 15-8 of the 16-bit CRC result.
Note: Upon initiation of an automatic CRC calculation, the third opcode byte fetched from program memory is indeterminate. Therefore, writes to CRC0CN that initiate a CRC operation must be immediately followed by a benign 3-byte instruction whose third byte is a don't care. An example of such an instruction is a 3-byte MOV that targets the CRC0FLIP register. When programming in `C', the dummy value written to CRC0FLIP should be a non-zero value to prevent the compiler from generating a 2-byte MOV instruction.
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SFR Definition 15.2. CRC0IN: CRC0 Data Input
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
CRC0IN[7:0] R/W 0 0 0 0
SFR Page = 0xF; SFR Address = 0x93 Bit Name 7:0 CRC0IN[7:0] CRC0 Data Input.
Function
Each write to CRC0IN results in the written data being computed into the existing CRC result according to the CRC algorithm described in Section 15.1
SFR Definition 15.3. CRC0DAT: CRC0 Data Output
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
CRC0DAT[7:0] R/W 0 0 0 0
SFR Page = 0xF; SFR Address = 0x91 Bit Name 7:0 CRC0DAT[7:0] CRC0 Data Output.
Function
Each read or write performed on CRC0DAT targets the CRC result bits pointed to by the CRC0 Result Pointer (CRC0PNT bits in CRC0CN).
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SFR Definition 15.4. CRC0AUTO: CRC0 Automatic Control
Bit Name Type Reset 0 1 0 7 AUTOEN 6 CRCDONE R/W 0 0 0 0 5 4 3 2 1 0
CRC0ST[5:0] R/W 0
SFR Page = 0xF; SFR Address = 0x96 Bit Name 7 AUTOEN
Function
Automatic CRC Calculation Enable. When AUTOEN is set to 1, any write to CRC0CN will initiate an automatic CRC starting at Flash sector CRC0ST and continuing for CRC0CNT sectors.
6
CRCDONE
CRCDONE Automatic CRC Calculation Complete. Set to 0 when a CRC calculation is in progress. Code execution is stopped during a CRC calculation; therefore, reads from firmware will always return 1.
5:0
CRC0ST[5:0]
Automatic CRC Calculation Starting Flash Sector. These bits specify the Flash sector to start the automatic CRC calculation. The starting address of the first Flash sector included in the automatic CRC calculation is CRC0ST x Page Size.
Note: `F91x and `F90x devices have a page size of 512 bytes.
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SFR Definition 15.5. CRC0CNT: CRC0 Automatic Flash Sector Count
Bit Name Type Reset 0 0 0 R/W 0 0 0 0 7 6 5 4 3 2 1 0
CRC0CNT[5:0] R/W 0
SFR Page = 0xF; SFR Address = 0x97 Bit Name 7:6 5:0 Unused Unused. Read = 00b; Write = Don't Care.
Function
CRC0CNT[5:0] Automatic CRC Calculation Flash Sector Count. These bits specify the number of Flash sectors to include in an automatic CRC calculation. The starting address of the last Flash sector included in the automatic CRC calculation is (CRC0ST+CRC0CNT) x Page Size.
Note: `F91x and `F90x devices have a page size of 512 bytes.
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15.5. CRC0 Bit Reverse Feature
CRC0 includes hardware to reverse the bit order of each bit in a byte as shown in Figure 15.2. Each byte of data written to CRC0FLIP is read back bit reversed. For example, if 0xC0 is written to CRC0FLIP, the data read back is 0x03. Bit reversal is a useful mathematical function used in algorithms such as the FFT.
CRC0FLIP Write
CRC0FLIP Read
Figure 15.2. Bit Reverse Register
SFR Definition 15.6. CRC0FLIP: CRC0 Bit Flip
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
CRC0FLIP[7:0] R/W 0 0 0 0
SFR Page = 0xF; SFR Address = 0x95 Bit Name 7:0 CRC0FLIP[7:0] CRC0 Bit Flip.
Function
Any byte written to CRC0FLIP is read back in a bit-reversed order, i.e. the written LSB becomes the MSB. For example: If 0xC0 is written to CRC0FLIP, the data read back will be 0x03. If 0x05 is written to CRC0FLIP, the data read back will be 0xA0.
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16. On-Chip DC-DC Converter (DC0)
C8051F91x-C8051F90x devices include an on-chip dc-dc converter to allow operation from a single cell battery with a supply voltage as low as 0.9 V. The dc-dc converter is a switching boost converter with an input voltage range of 0.9 to 1.8 V (C8051F911/01) or 3.6 V (C8051F912/11) and a programmable output voltage range of 1.8 to 3.3 V. The default output voltage is 1.9 V when the input is less than 1.9 V. Since the dc-dc converter uses a boost architecture, the output voltage will always be greater than or equal to the input voltage. The dc-dc converter can supply the system with up to 65 mW of regulated power (or up to 100 mW in some applications) and can be used for powering other devices in the system. This allows the most flexibility when interfacing to sensors and other analog signals which typically require a higher supply voltage than a single-cell battery can provide. Figure 16.1 shows a block diagram of the dc-dc converter. During normal operation in the first half of the switching cycle, the Duty Cycle Control switch is closed and the Diode Bypass switch is open. Since the output voltage is higher than the voltage at the DCEN pin, no current flows through the diode and the load is powered from the output capacitor. During this stage, the DCEN pin is connected to ground through the Duty Cycle Control switch, generating a positive voltage across the inductor and forcing its current to ramp up. In the second half of the switching cycle, the Duty Cycle control switch is opened and the Diode Bypass switch is closed. This connects DCEN directly to VDD/DC+ and forces the inductor current to charge the output capacitor. Once the inductor transfers its stored energy to the output capacitor, the Duty Cycle Control switch is closed, the Diode Bypass switch is opened, and the cycle repeats. The dc-dc converter has a built in voltage reference and oscillator, and will automatically limit or turn off the switching activity in case the peak inductor current rises beyond a safe limit or the output voltage rises above the programmed target value. This allows the dc-dc converter output to be safely overdriven by a secondary power source (when available) in order to preserve battery life. The dc-dc converter's settings can be modified using SFR registers which provide the ability to change the target output voltage, oscillator frequency or source, Diode Bypass switch resistance, peak inductor current, and minimum duty cycle.
VBAT 0.68 uH DCEN 4.7 uF
Duty Cycle Control
DC/DC Converter
VDD/DC+
Diode Bypass Control Logic DC0CN DC0CF DC0MD Voltage Reference DC/DC Oscillator
1uF
Iload
Cload
GND
Lparasitic
Lparasitic
GND/DC-
Figure 16.1. DC-DC Converter Block Diagram
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16.1. Startup Behavior
On initial power-on, the dc-dc converter outputs a constant 50% duty cycle until there is sufficient voltage on the output capacitor to maintain regulation. The size of the output capacitor and the amount of load current present during startup will determine the length of time it takes to charge the output capacitor. During initial power-on reset, the maximum peak inductor current threshold, which triggers the overcurrent protection circuit, is set to approximately 125 mA. This generates a "soft-start" to limit the output voltage slew rate and prevent excessive in-rush current at the output capacitor. In order to ensure reliable startup of the dc-dc converter, the following restrictions have been imposed: * The maximum dc load current allowed during startup is given in Table 4.16 on page 60. If the dc-dc converter is powering external sensors or devices through the VDD/DC+ pin or through GPIO pins, then the current supplied to these sensors or devices is counted towards this limit. The in-rush current into capacitors does not count towards this limit. The maximum total output capacitance is given in Table 4.16 on page 60. This value includes the required 1 F ceramic output capacitor and any additional capacitance connected to the VDD/DC+ pin.
*
Once initial power-on is complete, the peak inductor current limit can be increased by software as shown in Table 16.1. Limiting the peak inductor current can allow the device to start up near the battery's end of life.
.
Table 16.1. IPeak Inductor Current Limit Settings
SWSEL 1 1 0 0 ILIMIT 0 1 0 1 Peak Current (mA) Normal Power Mode 100 125 250 500 Peak Current (mA) Low Power Mode 75 100 125 250
The peak inductor current is dependent on several factors including the dc load current and can be estimated using following equation:
I PK =
efficiency = 0.80 inductance = 0.68 H frequency = 2.4 MHz
2 I LOAD VDD/DC+ - VBAT -----------------------------------------------------------------------------------------efficiency inductance frequency
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16.2. High Power Applications
The dc-dc converter is designed to provide the system with 65 mW of output power, however, it can safely provide up to 100 mW of output power without any risk of damage to the device. For high power applications, the system should be carefully designed to prevent unwanted VBAT and VDD/DC+ Supply Monitor resets, which are more likely to occur when the dc-dc converter output power exceeds 65mW. In addition, output power above 65 mW causes the dc-dc converter to have relaxed output regulation, high output ripple and more analog noise. At high output power, an inductor with low DC resistance should be chosen in order to minimize power loss and maximize efficiency. The combination of high output power and low input voltage will result in very high peak and average inductor currents. If the power supply has a high internal resistance, the transient voltage on the VBAT terminal could drop below 0.9 V and trigger a VBAT Supply Monitor Reset, even if the open-circuit voltage is well above the 0.9 V threshold. While this problem is most often associated with operation from very small batteries or batteries that are near the end of their useful life, it can also occur when using bench power supplies that have a slow transient response; the supply's display may indicate a voltage above 0.9 V, but the minimum voltage on the VBAT pin may be lower. A similar problem can occur at the output of the dc-dc converter: using the default low current limit setting (125 mA) can trigger VDD Supply Monitor resets if there is a high transient load current, particularly if the programmed output voltage is at or near 1.8 V.
16.3. Pulse Skipping Mode
The dc-dc converter allows the user to set the minimum pulse width such that if the duty cycle needs to decrease below a certain width in order to maintain regulation, an entire "clock pulse" will be skipped. Pulse skipping can provide substantial power savings, particularly at low values of load current. The converter will continue to maintain a minimum output voltage at its programmed value when pulse skipping is employed, though the output voltage ripple can be higher. Another consideration is that the dc-dc will operate with pulse-frequency modulation rather than pulse-width modulation, which makes the switching frequency spectrum less predictable; this could be an issue if the dc-dc converter is used to power a radio. Figure 4.5 and Figure 4.6 on page 45 and 46 show the effect of pulse skipping on power consumption.
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16.4. Enabling the DC-DC Converter
On power-on reset, the state of the DCEN pin is sampled to determine if the device will power up in onecell or two-cell mode. In two-cell mode, the dc-dc converter always remains disabled. In one-cell mode, the dc-dc converter remains disabled in Sleep Mode, and enabled in all other power modes. See Section "14. Power Management" on page 143 for complete details on available power modes. The dc-dc converter is enabled (one-cell mode) in hardware by placing a 0.68 H inductor between DCEN and VBAT. The dc-dc converter is disabled (two-cell mode) by shorting DCEN directly to GND. The DCEN pin should never be left floating. The device can only switch between one-cell and two-cell mode during a power-on reset. See Section "18. Reset Sources" on page 171 for more information regarding reset behavior. Figure 16.2 shows the two dc-dc converter configuration options.
0.68 uH
DC-DC Converter Enabled 0.9 to 3.6 V (`F912/02) 0.9 to 1.8 V (`F911/01) Supply Voltage (one-cell mode)
4.7 uF VBAT GND
1uF
DCEN VDD/DC+ GND/DC-
DC-DC Converter Disabled 1.8 to 3.6 V Supply Voltage (two-cell mode)
VBAT
GND
DCEN VDD/DC+ GND/DC-
Figure 16.2. DC-DC Converter Configuration Options
When the dc-dc converter "Enabled" configuration (one-cell mode) is chosen, the following guidelines apply: * * * * * In most cases, the GND/DC- pin should not be externally connected to GND. The 0.68 H inductor should be placed as close as possible to the DCEN pin for maximum efficiency. The 4.7 F capacitor should be placed as close as possible to the inductor. The current loop including GND, the 4.7 F capacitor, the 0.68 H inductor and the DCEN pin should be made as short as possible. The PCB traces connecting VDD/DC+ to the output capacitor and the output capacitor to GND/DC- should be as short and as thick as possible in order to minimize parasitic inductance.
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16.5. Minimizing Power Supply Noise
To minimize noise on the power supply lines, the GND and GND/DC- pins should be kept separate, as shown in Figure 16.2; one or the other should be connected to the pc board ground plane. For applications in which the dc-dc converter is used only to power internal circuits, the GND pin is normally connected to the board ground. The large decoupling capacitors in the input and output circuits ensure that each supply is relatively quiet with respect to its own ground. However, connecting a circuit element "diagonally" (e.g. connecting an external chip between VDD/DC+ and GND, or between VBAT and GND/DC-) can result in high supply noise across that circuit element. For applications in which the dc-dc converter is used to power external analog circuitry, it is recommended to connect the GND/DC- pin to the board ground and connect the battery's negative terminal to the GND pin only, which is not connected to board ground. To accommodate situations in which ADC0 is sampling a signal that is referenced to one of the external grounds, we recommend using the Analog Ground Reference (P0.1/AGND) option described in Section 5.12. This option prevents any voltage differences between the internal chip ground and the external grounds from modulating the ADC input signal. If this option is enabled, the P0.1 pin should be tied to the ground reference of the external analog input signal. When using the ADC with the dc-dc converter, we also recommend enabling the SYNC bit in the DC0CN register to minimize interference. These general guidelines provide the best performance in most applications, though some situations may benefit from experimentation to eliminate any residual noise issues. Examples might include tying the grounds together, using additional low-inductance decoupling caps in parallel with the recommended ones, investigating the effects of different dc-dc converter settings, etc.
16.6. Selecting the Optimum Switch Size
The dc-dc converter has two built-in switches (the diode bypass switch and duty cycle control switch). To maximize efficiency, one of two switch sizes may be selected. The large switches are ideal for carrying high currents and the small switches are ideal for low current applications. The ideal switchover point to switch from the small switches to the large switches varies with the programmed output voltage. At an output voltage of 2 V, the ideal switchover point is at approximately 4 mA total output current. At an output voltage of 3 V, the ideal switchover point is at approximately 8 mA total output current.
16.7. DC-DC Converter Clocking Options
The dc-dc converter may be clocked from its internal oscillator, or from any system clock source, selectable by the CLKSEL bit (DC0CF.0). The dc-dc converter internal oscillator frequency is approximately 2.4 MHz. For a more accurate clock source, the system clock, or a divided version of the system clock may be used as the dc-dc clock source. The dc-dc converter has a built in clock divider (configured using DC0CF[6:5]) which allows any system clock frequency over 1.6 MHz to generate a valid clock in the range of 1.6 to 3.2 MHz. When the precision internal oscillator is selected as the system clock source, the OSCICL register may be used to fine tune the oscillator frequency and the dc-dc converter clock. The oscillator frequency should only be decreased since it is factory calibrated at its maximum frequency. The minimum frequency which can be reached by the oscillator after taking into account process variations is approximately 16 MHz. The system clock routed to the dc-dc converter clock divider also may be inverted by setting the CLKINV bit (DC0CF.3) to logic 1. These options can be used to minimize interference in noise sensitive applications.
16.8. DC-DC Converter Behavior in Sleep Mode
When the C8051F91x-C8051F90x devices are placed in Sleep mode, the dc-dc converter is disabled, and the VDD/DC+ output is internally connected to VBAT by default. This behavior ensures that the GPIO pins are powered from a low-impedance source during sleep mode. If the GPIO pins are not used as inputs or
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outputs during sleep mode, then the VDD/DC+ output can be made to float during Sleep mode by setting the VDDSLP bit in the DC0CF register to 1. Setting this bit can provide power savings in two ways. First, if the sleep interval is relatively short and the VDD/DC+ load current (include leakage currents) is negligible, then the capacitor on VDD/DC+ will maintain the output voltage near the programmed value, which means that the VDD/DC+ capacitor will not need to be recharged upon every wake up event. The second power advantage is that internal or external lowpower circuits that require more than 1.8 V can continue to function during Sleep mode without operating the dc-dc converter, powered by the energy stored in the 1 F output decoupling capacitor. For example, the C8051F91x-C8051F90x comparators require about 0.4 A when operating in their lowest power mode. If the dc-dc converter output were increased to 3.3 V just before putting the device into Sleep mode, then the comparator could be powered for more than 3 seconds before the output voltage dropped to 1.8 V. In this example, the overall energy consumption would be much lower than if the dc-dc converter were kept running to power the comparator. If the load current on VDD/DC+ is high enough to discharge the VDD/DC+ capacitance to a voltage lower than VBAT during the sleep interval, an internal diode will prevent VDD/DC+ from dropping more than a few hundred millivolts below VBAT. There may be some additional leakage current from VBAT to ground when the VDD/DC+ level falls below VBAT, but this leakage current should be small compared to the current from VDD/DC+. The amount of time that it takes for a device configured in one-cell mode to wake up from Sleep mode depends on a number of factors, including the dc-dc converter clock speed, the settings of the SWSEL, ILIMIT, and LPEN bits, the battery internal resistance, the load current, and the difference between the VBAT voltage level and the programmed output voltage. The wake up time can be as short as 2 s, though it is more commonly in the range of 5 to 10 s, and it can exceed 50 s under extreme conditions. See Section "14. Power Management" on page 143 for more information about sleep mode.
16.9. Bypass Mode (C8051F912/02 only)
During normal operation, if the dc-dc converter input voltage exceeds the programmed output voltage, the converter will stop switching and the Diode Bypass switch will remain in the "on" state. The output voltage will be equal to the input voltage minus any resistive loss in the switch and all of the converter's analog circuits will remain biased. The bypass feature automatically shuts off the dc-dc converter when the input voltage is greater than the programmed output voltage by 150 mV. In bypass, the Diode Bypass switch and dc-dc converter bias currents are disabled except for the voltage comparison circuitry (~ 3 A, depending on the configuration settings in the DC0MD register). If the input voltage drops within 50 mV of the programmed output value, then the dc-dc converter automatically starts operating in the normal state. There is 100 mV voltage hysteresis built in the bypass comparator to enhance stability. The bypass mode increases system operating time in systems which have a minimum operating voltage higher than the battery end of life voltage. For instance, if an external chip requires a minimum supply voltage of 2.7 V and a lithium coin cell battery is used as power source (end-of-life voltage is approximately 2 V), then the C8051F912/902's dc-dc converter could be configured for an output voltage of 2.7 V with bypass mode enabled. The dc-dc converter would be bypassed when the battery was fresh, but as soon as the battery voltage dropped below 2.75 V, the dc-dc converter would turn on to ensure that the external chip was provided with a minimum of 2.7 V for the remainder of the battery life.
16.10. Low Power Mode (C8051F912/02 only)
Setting the LPEN bit in the DC0CF register will enable a Low Power Mode for the dc-dc converter. In Low Power Mode, the bias currents are substantially reduced, which can lead to an efficiency improvement with light load currents (generally less than a few mA). The drawback to this mode is that the response time of the converter's analog blocks is increased; larger delay in the circuits controlling the Diode Bypass switch can lead to loss of efficiency at medium and high load currents due to reverse leakage in the switch. The Low power mode also reduces the peak inductor current limit as shown in Table 16.1.
Rev. 1.0
165
C8051F91x-C8051F90x
16.11. Passive Diode Mode (C8051F912/02 only)
Setting the EXTDEN bit in DC0MD enables the Passive Diode Mode. In this mode, the control circuits for the Diode Bypass switch are disabled, which reduces the converter's quiescent operating current. An external Schottky diode may be connected between the DCEN (anode) and VDD/DC+ (cathode) pins. Under light load conditions, an external diode is typically not required. There are two situations in which this mode can prove beneficial. First is with very light load currents, where the efficiency is dominated by the converter's quiescent current. The converter will use an internal p-n junction diode to transfer current from the inductor to the output capacitor; although there is a larger voltage drop (and power loss) across a passive diode, the overall efficiency may be improved due to the reduction in quiescent current. The second situation is when output power is very high. In that case, efficiency can suffer because some reverse current can flow in the Diode Bypass switch before the control circuitry turns the switch off. Putting the device in Passive Diode Mode and optionally connecting an external Schottky diode between the DCEN and VDD/DC+ pins (parallel to the internal diode) may provide higher efficiency in some applications than using the internal Diode Bypass switch.
166
Rev. 1.0
C8051F91x-C8051F90x
16.12. DC-DC Converter Register Descriptions
The SFRs used to configure the dc-dc converter are described in the following register descriptions. The reset values for these registers can be used as-is in most systems; therefore, no software intervention or initialization is required.
SFR Definition 16.1. DC0CN: DC-DC Converter Control
Bit Name Type Reset 0 7 MINPW R/W 0 6 5 SWSEL R/W 1 4 Reserved R/W 0 3 SYNC R/W 0 0 2 1 VSEL R/W 0 1 0
SFR Page = 0x0; SFR Address = 0x97 Bit Name 7:6
Function
MINPW[1:0] DC-DC Converter Minimum Pulse Width. Specifies the minimum pulse width. 00: No minimum duty cycle. 01: Minimum pulse width is 20 ns. 10: Minimum pulse width is 40 ns. 11: Minimum pulse width is 80 ns.
5
SWSEL
DC-DC Converter Switch Select. Selects one of two possible converter switch sizes to maximize efficiency. 0: The large switches are selected (best efficiency for high output currents). 1: The small switches are selected (best efficiency for low output currents).
4 3
Reserved SYNC
Reserved. Always Write to 0. ADC0 Synchronization Enable. When synchronization is enabled, the ADC0SC[4:0] bits in the ADC0CF register must be set to 00000b. 0: The ADC is not synchronized to the dc-dc converter. 1: The ADC is synchronized to the dc-dc converter. ADC0 tracking is performed during the longest quiet time of the dc-dc converter switching cycle and ADC0 SAR clock is also synchronized to the dc-dc converter switching cycle.
2:0
VSEL[2:0]
DC-DC Converter Output Voltage Select. Specifies the target output voltage. 000: Target output voltage is 1.8 V. 001: Target output voltage is 1.9 V. 010: Target output voltage is 2.0 V. 011: Target output voltage is 2.1 V. 100: Target output voltage is 2.4 V. 101: Target output voltage is 2.7 V. 110: Target output voltage is 3.0 V. 111: Target output voltage is 3.3 V.
Rev. 1.0
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C8051F91x-C8051F90x
SFR Definition 16.2. DC0CF: DC-DC Converter Configuration
Bit Name Type Reset 7 LPEN R/W 0 6 R/W 0 5 R/W 0 4 AD0CKINV R/W 0 3 CLKINV R/W 0 Function 2 ILIMIT R/W 0 1 VDDSLP R/W 0 0 CLKSEL R/W 0
CLKDIV[1:0]
SFR Page = 0x0; SFR Address = 0x96 Bit Name 7 LPEN Low Power Mode Enable.
Enables the dc-dc low power mode which reduces bias currents, reduces peak inductor current, and increases efficiency for low load currents. Only available on `F912 and `F902 devices. 0: Low Power Mode Disabled. 1: Low Power Mode Enabled. CLKDIV[1:0] DC-DC Clock Divider. Divides the dc-dc converter clock when the system clock is selected as the clock source for dc-dc converter. These bits are ignored when the dc-dc converter is clocked from its local oscillator. 00: The dc-dc converter clock is system clock divided by 1. 01: The dc-dc converter clock is system clock divided by 2. 10: The dc-dc converter clock is system clock divided by 4. 11: The dc-dc converter clock is system clock divided by 8. AD0CKINV ADC0 Clock Inversion (Clock Invert During Sync). Inverts the ADC0 SAR clock derived from the dc-dc converter clock when the SYNC bit (DC0CN.3) is enabled. This bit is ignored when the SYNC bit is set to zero. 0: ADC0 SAR clock is inverted. 1: ADC0 SAR clock is not inverted. CLKINV DC-DC Converter Clock Invert. Inverts the system clock used as the input to the dc-dc clock divider. 0: The dc-dc converter clock is not inverted. 1: The dc-dc converter clock is inverted. 2 ILIMIT Peak Current Limit Threshold. Sets the threshold for the maximum allowed peak inductor current according to Table 16.1. 1 VDDSLP VDD-DC+ Sleep Mode Connection. Specifies the power source for VDD/DC+ in Sleep Mode when the dc-dc converter is enabled. 0: VDD-DC+ connected to VBAT in Sleep Mode. 1: VDD-DC+ is floating in Sleep Mode. DC-DC Converter Clock Source Select. Specifies the dc-dc converter clock source. 0: The dc-dc converter is clocked from its local oscillator. 1: The dc-dc converter is clocked from the system clock.
6:5
4
3
0
CLKSEL
168
Rev. 1.0
C8051F91x-C8051F90x
SFR Definition 16.3. DC0MD: DC-DC Mode
Bit Name Type Reset R/W 0 R/W 0 R/W 0 R/W 0 7 6 5 4 3 BYPFLG R Varies Function 0 2 R/W 0 1 0 PASDEN R/W 0
BYPSEL[1:0]
SFR Page = 0xF; SFR Address = 0x94 Bit Name 7:4 3 Unused BYPFLG Unused. Read = 0000b, Write = don't care. Bypass Indicator.
Indicates when the dc-dc converter is operating in bypass mode. Only available on `F912 and `F902 devices. 0: DC0 is not operating in bypass mode. 1: DC0 is operating in bypass mode. 2:1 BYPSEL[1:0] Bypass Mode Select. Selects the bypass settings. Only available on `F912 and `F902 devices. 00: Bypass mode disabled (highest supply current when the input voltage exceeds the programmed output voltage). 01: Bypass enabled (auto switch), dc-dc oscillator enabled (fast response time) 10: Bypass enabled (auto switch), dc-dc oscillator disabled (reduced supply current) 11: The dc-dc converter is forced into bypass mode (lowest supply current when the input voltage exceeds the programmed output voltage). 0 PASDEN Passive Diode Mode Enable. Passive external diode mode. Only available on `F912 and `F902 devices. 0: Passive diode mode disabled. 1: Passive diode mode enabled.
16.13. DC-DC Converter Specifications
See Table 4.16 on page 60 for a detailed listing of dc-dc converter specifications.
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C8051F91x-C8051F90x
17. Voltage Regulator (VREG0)
C8051F91x-C8051F90x devices include an internal voltage regulator (VREG0) to regulate the internal core supply to 1.8 V from a VDD/DC+ supply of 1.8 to 3.6 V. Electrical characteristics for the on-chip regulator are specified in the Electrical Specifications chapter. The REG0CN register allows the Precision Oscillator Bias to be disabled, reducing supply current in all non-Sleep power modes. This bias should only be disabled when the precision oscillator is not being used. The internal regulator (VREG0) is disabled when the device enters Sleep Mode and remains enabled when the device enters Suspend Mode. See Section "14. Power Management" on page 143 for complete details about low power modes.
SFR Definition 17.1. REG0CN: Voltage Regulator Control
Bit Name Type Reset R 0 7 6 Reserved R/W 0 5 Reserved R/W 0 4 OSCBIAS R/W 1 R 0 R 0 R 0 3 2 1 0 Reserved R/W 0
SFR Page = 0x0; SFR Address = 0xC9
Bit
7 6 5 4
Name
Unused Unused. Read = 0b. Write = Don't care. Reserved Reserved. Read = 0b. Must Write 0b. Reserved Reserved. Read = 0b. Must Write 0b. OSCBIAS Precision Oscillator Bias.
Function
When set to 1, the bias used by the precision oscillator is forced on. If the precision oscillator is not being used, this bit may be cleared to 0 to save approximately 80 A of supply current in all non-Sleep power modes. If disabled then re-enabled, the precision oscillator bias requires 4 s of settling time. 3:1 0 Unused Unused. Read = 000b. Write = Don't care. Reserved Reserved. Read = 0b. Must Write 0b.
17.1. Voltage Regulator Electrical Specifications
See Table 4.15 on page 59 for detailed Voltage Regulator Electrical Specifications.
170
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C8051F91x-C8051F90x
18. Reset Sources
Reset circuitry allows the controller to be easily placed in a predefined default condition. On entry to this reset state, the following occur: * * * * CIP-51 halts program execution Special Function Registers (SFRs) are initialized to their defined reset values External Port pins are forced to a known state Interrupts and timers are disabled
All SFRs are reset to the predefined values noted in the SFR descriptions. The contents of RAM are unaffected during a reset; any previously stored data is preserved as long as power is not lost. Since the stack pointer SFR is reset, the stack is effectively lost, even though the data on the stack is not altered. The Port I/O latches are reset to 0xFF (all logic ones) in open-drain mode. Weak pullups are enabled during and after the reset. For VDD Monitor and power-on resets, the RST pin is driven low until the device exits the reset state. On exit from the reset state, the program counter (PC) is reset, and the system clock defaults to an internal oscillator. Refer to Section "19. Clocking Sources" on page 179 for information on selecting and configuring the system clock source. The Watchdog Timer is enabled with the system clock divided by 12 as its clock source (Section "26.4. Watchdog Timer Mode" on page 304 details the use of the Watchdog Timer). Program execution begins at location 0x0000.
VDD/DC+
VBAT
Px.x Px.x
Comparator 0
+ C0RSEF
Supply Monitor
+ Enable
Power On Reset (wired-OR) '0'
RST
SmaRTClock
RTC0RE Missing Clock Detector (oneshot)
EN
Reset Funnel
PCA WDT
(Software Reset)
SWRSF
EN
MCD Enable
System Clock
CIP-51 Microcontroller Core
Extended Interrupt Handler
WDT Enable
Illegal Flash Operation
System Reset Power Management Block (PMU0)
System Reset
Power-On Reset Reset
Figure 18.1. Reset Sources
Rev. 1.0
171
C8051F91x-C8051F90x
18.1. Power-On (VBAT Supply Monitor) Reset
During power-up, the device is held in a reset state and the RST pin is driven low until VBAT settles above VPOR. An additional delay occurs before the device is released from reset; the delay decreases as the VBAT ramp time increases (VBAT ramp time is defined as how fast VBAT ramps from 0 V to VPOR). Figure 18.3 plots the power-on and VDD monitor reset timing. For valid ramp times (less than 3 ms), the power-on reset delay (TPORDelay) is typically 3 ms (VBAT = 0.9 V), 7 ms (VBAT = 1.8 V), or 15 ms (VBAT = 3.6 V).
Note: The maximum VDD ramp time is 3 ms; slower ramp times may cause the device to be released from reset before VBAT reaches the VPOR level.
On exit from a power-on reset, the PORSF flag (RSTSRC.1) is set by hardware to logic 1. When PORSF is set, all of the other reset flags in the RSTSRC Register are indeterminate (PORSF is cleared by all other resets). Since all resets cause program execution to begin at the same location (0x0000), software can read the PORSF flag to determine if a power-up was the cause of reset. The contents of internal data memory should be assumed to be undefined after a power-on reset. On `F912 and `F902 devices, the VBAT supply monitor can be disabled to save power by writing `1' to the MONDIS (PMU0MD.5) bit. When the VBAT supply monitor is disabled, all reset sources will trigger a full POR and will re-enable the VBAT supply monitor.
volts
VBAT VPOR
~0.8 0.6
~0.5 See specification table for min/max voltages.
t
Logic HIGH
RST
VB AT
TPORDelay Logic LOW
TPORDelay
Power-On Reset
Power-On Reset
Figure 18.2. Power-Fail Reset Timing Diagram
172
Rev. 1.0
C8051F91x-C8051F90x
18.2. Power-Fail (VDD/DC+ Supply Monitor) Reset
C8051F91x-C8051F90x devices have a VDD/DC+ Supply Monitor that is enabled and selected as a reset source after each power-on or power-fail reset. When enabled and selected as a reset source, any power down transition or power irregularity that causes VDD/DC+ to drop below VRST will cause the RST pin to be driven low and the CIP-51 will be held in a reset state (see Figure 18.3). When VDD/DC+ returns to a level above VRST, the CIP-51 will be released from the reset state. After a power-fail reset, the PORSF flag reads 1, the contents of RAM invalid, and the VDD/DC+ supply monitor is enabled and selected as a reset source. The enable state of the VDD/DC+ supply monitor and its selection as a reset source is only altered by power-on and power-fail resets. For example, if the VDD/DC+ supply monitor is de-selected as a reset source and disabled by software, then a software reset is performed, the VDD/DC+ supply monitor will remain disabled and de-selected after the reset. In battery-operated systems, the contents of RAM can be preserved near the end of the battery's usable life if the device is placed in Sleep Mode prior to a power-fail reset occurring. When the device is in Sleep Mode, the power-fail reset is automatically disabled and the contents of RAM are preserved as long as the VBAT supply does not fall below VPOR. A large capacitor can be used to hold the power supply voltage above VPOR while the user is replacing the battery. Upon waking from Sleep mode, the enable and reset source select state of the VDD/DC+ supply monitor are restored to the value last set by the user. To allow software early notification that a power failure is about to occur, the VDDOK bit is cleared when the VDD/DC+ supply falls below the VWARN threshold. The VDDOK bit can be configured to generate an interrupt. See Section "12. Interrupt Handler" on page 120 for more details. Important Note: To protect the integrity of Flash contents, the VDD/DC+ supply monitor must be enabled and selected as a reset source if software contains routines which erase or write Flash memory. If the VDD/DC+ supply monitor is not enabled, any erase or write performed on Flash memory will cause a Flash Error device reset.
volts
VDD/DC+
VDD WARN V RST VBAT VBAT WARN V POR
t
VDDOK SLEEP RST Active Mode Power-Fail Reset Sleep Mode RAM Retained - No Reset
Note: Wakeup signal required after new battery insertion
Figure 18.3. Power-Fail Reset Timing Diagram
Rev. 1.0
173
C8051F91x-C8051F90x
Important Notes: * The Power-on Reset (POR) delay is not incurred after a VDD/DC+ supply monitor reset. See Section "4. Electrical Characteristics" on page 36 for complete electrical characteristics of the VDD/DC+ monitor. Software should take care not to inadvertently disable the VDD Monitor as a reset source when writing to RSTSRC to enable other reset sources or to trigger a software reset. All writes to RSTSRC should explicitly set PORSF to 1 to keep the VDD Monitor enabled as a reset source. The VDD/DC+ supply monitor must be enabled before selecting it as a reset source. Selecting the VDD/DC+ supply monitor as a reset source before it has stabilized may generate a system reset. In systems where this reset would be undesirable, a delay should be introduced between enabling the VDD/DC+ supply monitor and selecting it as a reset source. See Section "4. Electrical Characteristics" on page 36 for minimum VDD/DC+ Supply Monitor turn-on time. No delay should be introduced in systems where software contains routines that erase or write Flash memory. The procedure for enabling the VDD/DC+ supply monitor and selecting it as a reset source is shown below: 1. Enable the VDD/DC+ Supply Monitor (VDMEN bit in VDM0CN = 1). 2. Wait for the VDD/DC+ Supply Monitor to stabilize (optional). 3. Select the VDD/DC+ Supply Monitor as a reset source (PORSF bit in RSTSRC = 1).
*
*
174
Rev. 1.0
C8051F91x-C8051F90x
SFR Definition 18.1. VDM0CN: VDD/DC+ Supply Monitor Control
Bit Name Type Reset 7 VDMEN R/W 1 6 VDDSTAT R Varies 5 VDDOK R Varies 4 VBATOK R Varies 3 2 1 0
VDDOKIE VBATOKIE R/W 1 R/W 0 R/W 0 R/W 0
SFR Page = 0x0; SFR Address = 0xFF Bit Name 7 VDMEN VDD/DC+ Supply Monitor Enable.
Function
This bit turns the VDD/DC+ supply monitor circuit on/off. The VDD/DC+ Supply Monitor cannot generate system resets until it is also selected as a reset source in register RSTSRC (SFR Definition 18.2). 0: VDD/DC+ Supply Monitor Disabled. 1: VDD/DC+ Supply Monitor Enabled. 6 VDDSTAT VDD/DC+ Supply Status. This bit indicates the current power supply status. 0: VDD/DC+ is at or below the VRST threshold. 1: VDD/DC+ is above the VRST threshold. 5 VDDOK VDD/DC+ Supply Status (Early Warning). This bit indicates the current VDD/DC+ power supply status. 0: VDD/DC+ is at or below the VDDWARN threshold. 1: VDD/DC+ is above the VDDWARN threshold. 4 VBATOK VBAT Supply Status (Early Warning). This bit indicates the current VBAT power supply status. This bit is only present on `F912 and `F902 devices. 0: VBAT is at or below the VBATWARN threshold. 1: VBAT is above the VBATWARN threshold. 3 VDDOKIE VDD/DC+ Early Warning Interrupt Enable. Enables the VDD/DC+ Early Warning Interrupt. This bit only has an effect on `F912 and `F902 devices. All other devices behave as if this bit is set to 1. 0: VDD/DC+ Early Warning Interrupt is disabled. 1: VDD/DC+ Early Warning Interrupt is enabled. 2 VBATOKIE VBAT Early Warning Interrupt Enable. Enables the VBAT Early Warning Interrupt. This bit only has an effect on `F912 and `F902 devices. All other devices behave as if this bit is set to 0. 0: VBAT Early Warning Interrupt is disabled. 1: VBAT Early Warning Interrupt is enabled. 1:0 Unused Unused. Read = 00b. Write = Don't Care.
Rev. 1.0
175
C8051F91x-C8051F90x
18.3. External Reset
The external RST pin provides a means for external circuitry to force the device into a reset state. Asserting an active-low signal on the RST pin generates a reset; an external pullup and/or decoupling of the RST pin may be necessary to avoid erroneous noise-induced resets. See Table 4.4 for complete RST pin specifications. The external reset remains functional even when the device is in the low power suspend and sleep modes. The PINRSF flag (RSTSRC.0) is set on exit from an external reset.
18.4. Missing Clock Detector Reset
The Missing Clock Detector (MCD) is a one-shot circuit that is triggered by the system clock. If the system clock remains high or low for more than 100 s, the one-shot will time out and generate a reset. After a MCD reset, the MCDRSF flag (RSTSRC.2) will read 1, signifying the MCD as the reset source; otherwise, this bit reads 0. Writing a 1 to the MCDRSF bit enables the Missing Clock Detector; writing a 0 disables it. The missing clock detector reset is automatically disabled when the device is in the low power suspend or sleep mode. Upon exit from either low power state, the enabled/disabled state of this reset source is restored to its previous value. The state of the RST pin is unaffected by this reset.
18.5. Comparator0 Reset
Comparator0 can be configured as a reset source by writing a 1 to the C0RSEF flag (RSTSRC.5). Comparator0 should be enabled and allowed to settle prior to writing to C0RSEF to prevent any turn-on chatter on the output from generating an unwanted reset. The Comparator0 reset is active-low: if the noninverting input voltage (on CP0+) is less than the inverting input voltage (on CP0-), the device is put into the reset state. After a Comparator0 reset, the C0RSEF flag (RSTSRC.5) will read 1 signifying Comparator0 as the reset source; otherwise, this bit reads 0. The Comparator0 reset source remains functional even when the device is in the low power suspend and sleep states as long as Comparator0 is also enabled as a wake-up source. The state of the RST pin is unaffected by this reset.
18.6. PCA Watchdog Timer Reset
The programmable Watchdog Timer (WDT) function of the Programmable Counter Array (PCA) can be used to prevent software from running out of control during a system malfunction. The PCA WDT function can be enabled or disabled by software as described in Section "26.4. Watchdog Timer Mode" on page 304; the WDT is enabled and clocked by SYSCLK / 12 following any reset. If a system malfunction prevents user software from updating the WDT, a reset is generated and the WDTRSF bit (RSTSRC.5) is set to 1. The PCA Watchdog Timer reset source is automatically disabled when the device is in the low power suspend or sleep mode. Upon exit from either low power state, the enabled/disabled state of this reset source is restored to its previous value.The state of the RST pin is unaffected by this reset.
176
Rev. 1.0
C8051F91x-C8051F90x
18.7. Flash Error Reset
If a Flash read/write/erase or program read targets an illegal address, a system reset is generated. This may occur due to any of the following: * * * * * A Flash write or erase is attempted above user code space. This occurs when PSWE is set to 1 and a MOVX write operation targets an address above the Lock Byte address. A Flash read is attempted above user code space. This occurs when a MOVC operation targets an address above the Lock Byte address. A Program read is attempted above user code space. This occurs when user code attempts to branch to an address above the Lock Byte address. A Flash read, write or erase attempt is restricted due to a Flash security setting (see Section "13.3. Security Options" on page 134). A Flash write or erase is attempted while the VDD Monitor is disabled.
The FERROR bit (RSTSRC.6) is set following a Flash error reset. The state of the RST pin is unaffected by this reset.
18.8. SmaRTClock (Real Time Clock) Reset
The SmaRTClock can generate a system reset on two events: SmaRTClock Oscillator Fail or SmaRTClock Alarm. The SmaRTClock Oscillator Fail event occurs when the SmaRTClock Missing Clock Detector is enabled and the SmaRTClock clock is below approximately 20 kHz. A SmaRTClock alarm event occurs when the SmaRTClock Alarm is enabled and the SmaRTClock timer value matches the ALARMn registers. The SmaRTClock can be configured as a reset source by writing a 1 to the RTC0RE flag (RSTSRC.7). The SmaRTClock reset remains functional even when the device is in the low power Suspend or Sleep mode. The state of the RST pin is unaffected by this reset.
18.9. Software Reset
Software may force a reset by writing a 1 to the SWRSF bit (RSTSRC.4). The SWRSF bit will read 1 following a software forced reset. The state of the RST pin is unaffected by this reset.
Rev. 1.0
177
C8051F91x-C8051F90x
SFR Definition 18.2. RSTSRC: Reset Source
Bit Name Type Reset 7 RTC0RE R/W Varies 6 FERROR R Varies 5 C0RSEF R/W Varies 4 SWRSF R/W Varies 3 WDTRSF R Varies 2 MCDRSF R/W Varies 1 PORSF R/W Varies 0 PINRSF R Varies
SFR Page = 0x0; SFR Address = 0xEF. Bit Name Description 7 RTC0RE SmaRTClock Reset Enable and Flag
Write
Read
0: Disable SmaRTClock Set to 1 if SmaRTClock as a reset source. alarm or oscillator fail 1: Enable SmaRTClock as caused the last reset. a reset source. N/A Set to 1 if Flash read/write/erase error caused the last reset.
6
FERROR Flash Error Reset Flag.
5
C0RSEF Comparator0 Reset Enable and Flag.
0: Disable Comparator0 as Set to 1 if Comparator0 a reset source. caused the last reset. 1: Enable Comparator0 as a reset source. Writing a 1 forces a system reset. Set to 1 if last reset was caused by a write to SWRSF. Set to 1 if Watchdog Timer overflow caused the last reset.
4
SWRSF
Software Reset Force and Flag.
3
WDTRSF Watchdog Timer Reset Flag. N/A
2
MCDRSF Missing Clock Detector (MCD) Enable and Flag.
0: Disable the MCD. Set to 1 if Missing Clock Detector timeout caused 1: Enable the MCD. The MCD triggers a reset the last reset. if a missing clock condition is detected. 0: Disable the VDD/DC+ Supply Monitor as a reset source. 1: Enable the VDD/DC+ Supply Monitor as a reset source.3 N/A Set to 1 anytime a poweron or VDD monitor reset occurs.2
1
PORSF
Power-On / Power-Fail Reset Flag, and Power-Fail Reset Enable.
0
PINRSF
HW Pin Reset Flag.
Set to 1 if RST pin caused the last reset.
Notes: 1. It is safe to use read-modify-write operations (ORL, ANL, etc.) to enable or disable specific interrupt sources. 2. If PORSF read back 1, the value read from all other bits in this register are indeterminate. 3. Writing a 1 to PORSF before the VDD/DC+ Supply Monitor is stabilized may generate a system reset.
178
Rev. 1.0
C8051F91x-C8051F90x
19. Clocking Sources
C8051F91x-C8051F90x devices include a programmable precision internal oscillator, an external oscillator drive circuit, a low power internal oscillator, and a SmaRTClock real time clock oscillator. The precision internal oscillator can be enabled/disabled and calibrated using the OSCICN and OSCICL registers, as shown in Figure 19.1. The external oscillator can be configured using the OSCXCN register. The low power internal oscillator is automatically enabled and disabled when selected and deselected as a clock source. SmaRTClock operation is described in the SmaRTClock oscillator chapter. The system clock (SYSCLK) can be derived from the precision internal oscillator, external oscillator, low power internal oscillator, or SmaRTClock oscillator. The global clock divider can generate a system clock that is 1, 2, 4, 8, 16, 32, 64, or 128 times slower that the selected input clock source. Oscillator electrical specifications can be found in the Electrical Specifications Chapter.
OSCICL
Option 2 VDD Option 3 IOSCEN IFRDY
OSCICN
CLKSEL
CLKRDY CLKDIV2 CLKDIV1 CLKDIV0 CLKSL1 CLKSL0
XTAL2
XTAL2
EN Precision Internal Oscillator XTAL1 10M XTAL2 External Oscillator Drive Circuit External Oscillator n Low Power Internal Oscillator Clock Divider SmaRTClock Oscillator Option 4 XTAL2 SYSCLK
Precision Internal Oscillator
Option 1
CLKRDY
XTLVLD XOSCMD2 XOSCMD1 XOSCMD0
OSCXCN
Figure 19.1. Clocking Sources Block Diagram
The proper way of changing the system clock when both the clock source and the clock divide value are being changed is as follows: If switching from a fast "undivided" clock to a slower "undivided" clock: a. Change the clock divide value. b. Poll for CLKRDY > 1. c. Change the clock source. If switching from a slow "undivided" clock to a faster "undivided" clock: a. Change the clock source. b. Change the clock divide value. c. Poll for CLKRDY > 1.
XFCN2 XFCN1 XFCN0
Low Power Internal Oscillator
SmaRTClock Oscillator
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19.1. Programmable Precision Internal Oscillator
All C8051F91x-C8051F90x devices include a programmable precision internal oscillator that may be selected as the system clock. OSCICL is factory calibrated to obtain a 24.5 MHz frequency. See Section "4. Electrical Characteristics" on page 36 for complete oscillator specifications. The precision oscillator supports a spread spectrum mode which modulates the output frequency in order to reduce the EMI generated by the system. When enabled (SSE = 1), the oscillator output frequency is modulated by a stepped triangle wave whose frequency is equal to the oscillator frequency divided by 384 (63.8 kHz using the factory calibration). The deviation from the nominal oscillator frequency is +0%, -1.6%, and the step size is typically 0.26% of the nominal frequency. When using this mode, the typical average oscillator frequency is lowered from 24.5 MHz to 24.3 MHz.
19.2. Low Power Internal Oscillator
All C8051F91x-C8051F90x devices include a low power internal oscillator that defaults as the system clock after a system reset. The low power internal oscillator frequency is 20 MHz 10% and is automatically enabled when selected as the system clock and disabled when not in use. See Section "4. Electrical Characteristics" on page 36 for complete oscillator specifications.
19.3. External Oscillator Drive Circuit
All C8051F91x-C8051F90x devices include an external oscillator circuit that may drive an external crystal, ceramic resonator, capacitor, or RC network. A CMOS clock may also provide a clock input. Figure 19.1 shows a block diagram of the four external oscillator options. The external oscillator is enabled and configured using the OSCXCN register. The external oscillator output may be selected as the system clock or used to clock some of the digital peripherals (e.g. Timers, PCA, etc.). See the data sheet chapters for each digital peripheral for details. See Section "4. Electrical Characteristics" on page 36 for complete oscillator specifications.
19.3.1. External Crystal Mode
If a crystal or ceramic resonator is used as the external oscillator, the crystal/resonator and a 10 Mresistor must be wired across the XTAL1 and XTAL2 pins as shown in Figure 19.1, Option 1. Appropriate loading capacitors should be added to XTAL1 and XTAL2, and both pins should be configured for analog I/O with the digital output drivers disabled. Figure 19.2 shows the external oscillator circuit for a 20 MHz quartz crystal with a manufacturer recommended load capacitance of 12.5 pF. Loading capacitors are "in series" as seen by the crystal and "in parallel" with the stray capacitance of the XTAL1 and XTAL2 pins. The total value of the each loading capacitor and the stray capacitance of each XTAL pin should equal 12.5pF x 2 = 25 pF. With a stray capacitance of 10 pF per pin, the 15 pF capacitors yield an equivalent series capacitance of 12.5 pF across the crystal.
Note: The recommended load capacitance depends upon the crystal and the manufacturer. Please refer to the crystal data sheet when completing these calculations.
180
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15 pF XTAL1 25 MHz 10 Mohm XTAL2 15 pF
Figure 19.2. 25 MHz External Crystal Example
Important Note on External Crystals: Crystal oscillator circuits are quite sensitive to PCB layout. The crystal should be placed as close as possible to the XTAL pins on the device. The traces should be as short as possible and shielded with ground plane from any other traces which could introduce noise or interference. When using an external crystal, the external oscillator drive circuit must be configured by software for Crystal Oscillator Mode or Crystal Oscillator Mode with divide by 2 stage. The divide by 2 stage ensures that the clock derived from the external oscillator has a duty cycle of 50%. The External Oscillator Frequency Control value (XFCN) must also be specified based on the crystal frequency. The selection should be based on Table 19.1. For example, a 25 MHz crystal requires an XFCN setting of 111b.
Table 19.1. Recommended XFCN Settings for Crystal Mode
XFCN 000 001 010 011 100 101 110 111 Crystal Frequency f 20 kHz 20 kHz f 58 kHz 58 kHz f 155 kHz 155 kHz f 415 kHz 415 kHz f 1.1 MHz 1.1 MHz f 3.1 MHz 3.1 MHz f 8.2 MHz 8.2 MHz f 25 MHz Bias Current 0.5 A 1.5 A 4.8 A 14 A 40 A 120 A 550 A 2.6 mA Typical Supply Current (VDD = 2.4 V) 3.0 A, f = 32.768 kHz 4.8 A, f = 32.768 kHz 9.6 A, f = 32.768 kHz 28 A, f = 400 kHz 71 A, f = 400 kHz 193 A, f = 400 kHz 940 A, f = 8 MHz 3.9 mA, f = 25 MHz
When the crystal oscillator is first enabled, the external oscillator valid detector allows software to determine when the external system clock has stabilized. Switching to the external oscillator before the crystal oscillator has stabilized can result in unpredictable behavior. The recommended procedure for starting the crystal is as follows: 1. 2. 3. 4. Configure XTAL1 and XTAL2 for analog I/O and disable the digital output drivers. Configure and enable the external oscillator. Poll for XTLVLD => 1. Switch the system clock to the external oscillator.
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19.3.2. External RC Mode
If an RC network is used as the external oscillator, the circuit should be configured as shown in Figure 19.1, Option 2. The RC network should be added to XTAL2, and XTAL2 should be configured for analog I/O with the digital output drivers disabled. XTAL1 is not affected in RC mode. The capacitor should be no greater than 100 pF; however for very small capacitors, the total capacitance may be dominated by parasitic capacitance in the PCB layout. The resistor should be no smaller than 10 k. The oscillation frequency can be determined by the following equation:
f = 1.23 10 -----------------------RC
3
where f = frequency of clock in MHzR = pull-up resistor value in k VDD = power supply voltage in VoltsC = capacitor value on the XTAL2 pin in pF
To determine the required External Oscillator Frequency Control value (XFCN) in the OSCXCN Register, first select the RC network value to produce the desired frequency of oscillation. For example, if the frequency desired is 100 kHz, let R = 246 k and C = 50 pF:
f = 1.23 10 - = 1.23 10 - = 100 kHz ----------------------------------------------RC 246 50
3 3
where f = frequency of clock in MHz VDD = power supply voltage in Volts
R = pull-up resistor value in k C = capacitor value on the XTAL2 pin in pF
Referencing Table 19.2, the recommended XFCN setting is 010.
Table 19.2. Recommended XFCN Settings for RC and C modes
XFCN Approximate Frequency Range (RC and C Mode) f 25 kHz 25 kHz f 50 kHz 50 kHz f 100 kHz 100 kHz f 200 kHz 200 kHz f 400 kHz 400 kHz f 800 kHz 800 kHz f 1.6 MHz 1.6 MHz f 3.2 MHz K Factor (C Mode) Typical Supply Current/ Actual Measured Frequency (C Mode, VDD = 2.4 V) 3.0 A, f = 11 kHz, C = 33 pF 5.5 A, f = 33 kHz, C = 33 pF 13 A, f = 98 kHz, C = 33 pF 32 A, f = 270 kHz, C = 33 pF 82 A, f = 310 kHz, C = 46 pF 242 A, f = 890 kHz, C = 46 pF 1.0 mA, f = 2.0 MHz, C = 46 pF 4.6 mA, f = 6.8 MHz, C = 46 pF
000 001 010 011 100 101 110 111
K Factor = 0.87 K Factor = 2.6 K Factor = 7.7 K Factor = 22 K Factor = 65 K Factor = 180 K Factor = 664 K Factor = 1590
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When the RC oscillator is first enabled, the external oscillator valid detector allows software to determine when oscillation has stabilized. The recommended procedure for starting the RC oscillator is as follows: 1. 2. 3. 4. Configure XTAL2 for analog I/O and disable the digital output drivers. Configure and enable the external oscillator. Poll for XTLVLD => 1. Switch the system clock to the external oscillator.
19.3.3. External Capacitor Mode
If a capacitor is used as the external oscillator, the circuit should be configured as shown in Figure 19.1, Option 3. The capacitor should be added to XTAL2, and XTAL2 should be configured for analog I/O with the digital output drivers disabled. XTAL1 is not affected in RC mode. The capacitor should be no greater than 100 pF; however, for very small capacitors, the total capacitance may be dominated by parasitic capacitance in the PCB layout. The oscillation frequency and the required External Oscillator Frequency Control value (XFCN) in the OSCXCN Register can be determined by the following equation:
KF f = -------------------C V DD
where f = frequency of clock in MHzR = pull-up resistor value in k VDD = power supply voltage in VoltsC = capacitor value on the XTAL2 pin in pF Below is an example of selecting the capacitor and finding the frequency of oscillation Assume VDD = 3.0 V and f = 150 kHz:
KF f = -------------------C V DD KF 0.150 MHz = ----------------C 3.0
Since a frequency of roughly 150 kHz is desired, select the K Factor from Table 19.2 as KF = 22:
22 0.150 MHz = ---------------------C 3.0 V
22 C = ---------------------------------------------0.150 MHz 3.0 V
C = 48.8 pF
Therefore, the XFCN value to use in this example is 011 and C is approximately 50 pF. The recommended startup procedure for C mode is the same as RC mode.
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19.3.4. External CMOS Clock Mode
If an external CMOS clock is used as the external oscillator, the clock should be directly routed into XTAL2. The XTAL2 pin should be configured as a digital input. XTAL1 is not used in external CMOS clock mode. The external oscillator valid detector will always return zero when the external oscillator is configured to External CMOS Clock mode.
184
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19.4. Special Function Registers for Selecting and Configuring the System Clock
The clocking sources on C8051F91x-C8051F90x devices are enabled and configured using the OSCICN, OSCICL, OSCXCN and the SmaRTClock internal registers. See Section "20. SmaRTClock (Real Time Clock)" on page 188 for SmaRTClock register descriptions. The system clock source for the MCU can be selected using the CLKSEL register. To minimize active mode current, the oneshot timer which sets Flash read time should by bypassed when the system clock is greater than 10 MHz. See the FLSCL register description for details. The clock selected as the system clock can be divided by 1, 2, 4, 8, 16, 32, 64, or 128. When switching between two clock divide values, the transition may take up to 128 cycles of the undivided clock source. The CLKRDY flag can be polled to determine when the new clock divide value has been applied. The clock divider must be set to "divide by 1" when entering Suspend or Sleep Mode. The system clock source may also be switched on-the-fly. The switchover takes effect after one clock period of the slower oscillator.
SFR Definition 19.1. CLKSEL: Clock Select
Bit Name Type Reset 7 CLKRDY R 0 R/W 0 6 5 CLKDIV[2:0] R/W 1 R/W 1 R/W 0 R/W 1 4 3 2 1 CLKSEL[2:0] R/W 0 R/W 0 0
SFR Page = All Pages; SFR Address = 0xA9
Bit Name Function
7
CLKRDY
System Clock Divider Clock Ready Flag. 0: The selected clock divide setting has not been applied to the system clock. 1: The selected clock divide setting has been applied to the system clock. System Clock Divider Bits. Selects the clock division to be applied to the undivided system clock source. 000: System clock is divided by 1. 001: System clock is divided by 2. 010: System clock is divided by 4. 011: System clock is divided by 8. 100: System clock is divided by 16. 101: System clock is divided by 32. 110: System clock is divided by 64. 111: System clock is divided by 128. Unused. Read = 0b. Must Write 0b. System Clock Select. Selects the oscillator to be used as the undivided system clock source. 000: Precision Internal Oscillator. 001: External Oscillator. 011: SmaRTClock Oscillator. 100: Low Power Oscillator. All other values reserved.
6:4
CLKDIV[2:0]
3 2:0
Unused CLKSEL[2:0]
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C8051F91x-C8051F90x
SFR Definition 19.2. OSCICN: Internal Oscillator Control
Bit Name Type Reset 7 IOSCEN R/W 0 6 IFRDY R 0 R/W Varies R/W Varies 5 4 3 2 1 0
Reserved[5:0] R/W Varies R/W Varies R/W Varies R/W Varies
SFR Page = 0x0; SFR Address = 0xB2 Bit 7 Name IOSCEN Internal Oscillator Enable. 0: Internal oscillator disabled. 1: Internal oscillator enabled. 6 IFRDY Internal Oscillator Frequency Ready Flag. 0: Internal oscillator is not running at its programmed frequency. 1: Internal oscillator is running at its programmed frequency. 5:0 Reserved Reserved. Must perform read-modify-write.
Note: Read-modify-write operations such as ORL and ANL must be used to set or clear the enable bit of this register.
Function
SFR Definition 19.3. OSCICL: Internal Oscillator Calibration
Bit Name Type Reset 7 SSE R/W 0 R Varies R/W Varies R/W Varies 6 5 4 3 OSCICL[6:0] R/W Varies R/W Varies R/W Varies R/W Varies 2 1 0
SFR Page = 0x0; SFR Address = 0xB3 Bit 7 Name SSE Spread Spectrum Enable. 0: Spread Spectrum clock dithering disabled. 1: Spread Spectrum clock dithering enabled. 6:0 OSCICL Internal Oscillator Calibration. Factory calibrated to obtain a frequency of 24.5 MHz. Incrementing this register decreases the oscillator frequency and decrementing this register increases the oscillator frequency. The step size is approximately 1% of the calibrated frequency. The recommended calibration frequency range is between 16 and 24.5 MHz. Function
186
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SFR Definition 19.4. OSCXCN: External Oscillator Control
Bit 7 6 5 XOSCMD[2:0] R 0 R/W 0 R/W 0 4 3 Reserved R/W 0 R/W 0 2 1 XFCN[2:0] R/W 0 R/W 0 0
Name XCLKVLD Type Reset R 0
SFR Page = 0x0; SFR Address = 0xB1
Bit Name Function
7
XCLKVLD External Oscillator Valid Flag. Provides External Oscillator status and is valid at all times for all modes of operation except External CMOS Clock Mode and External CMOS Clock Mode with divide by 2. In these modes, XCLKVLD always returns 0. 0: External Oscillator is unused or not yet stable. 1: External Oscillator is running and stable.
6:4
XOSCMD External Oscillator Mode Bits. Configures the external oscillator circuit to the selected mode. 00x: External Oscillator circuit disabled. 010: External CMOS Clock Mode. 011: External CMOS Clock Mode with divide by 2 stage. 100: RC Oscillator Mode. 101: Capacitor Oscillator Mode. 110: Crystal Oscillator Mode. 111: Crystal Oscillator Mode with divide by 2 stage.
3 2:0
Reserved Reserved. Read = 0b. Must Write 0b. XFCN External Oscillator Frequency Control Bits. Controls the external oscillator bias current. 000-111: See Table 19.1 on page 181 (Crystal Mode) or Table 19.2 on page 182 (RC or C Mode) for recommended settings.
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20. SmaRTClock (Real Time Clock)
C8051F91x-C8051F90x devices include an ultra low power 32-bit SmaRTClock Peripheral (Real Time Clock) with alarm. The SmaRTClock has a dedicated 32 kHz oscillator that can be configured for use with or without a crystal. No external resistor or loading capacitors are required. The on-chip loading capacitors are programmable to 16 discrete levels allowing compatibility with a wide range of crystals. The SmaRTClock can operate directly from a 0.9-3.6 V battery voltage and remains operational even when the device goes into its lowest power down mode. On `F912 and `F902 devices, the SmaRTClock output can be buffered and routed to a GPIO pin to provide an accurate, low frequency clock to other devices while the MCU is in its lowest power down mode (see "PMU0MD: Power Management Unit Mode" on page 150 for more details). `F912 and `F902 devices also support an ultra low power internal LFO that reduces sleep mode current. The SmaRTClock allows a maximum of 36 hour 32-bit independent time-keeping when used with a 32.768 kHz Watch Crystal. The SmaRTClock provides an Alarm and Missing SmaRTClock events, which could be used as reset or wakeup sources. See Section "18. Reset Sources" on page 171 and Section "14. Power Management" on page 143 for details on reset sources and low power mode wake-up sources, respectively.
XTAL4 XTAL3 RTCOUT
Buffered clock output and LFO only available on `F912 and `F902 devices.
SmaRTClock
Programmable Load Capacitors SmaRTClock Oscillator
LFO
Power/ Clock Mgmt
32-Bit SmaRTClock Timer CIP-51 CPU Interface Registers RTC0KEY RTC0ADR RTC0DAT
SmaRTClock State Machine Wake-Up Interrupt
Internal Registers
CAPTUREn RTC0CN RTC0XCN RTC0XCF RTC0PIN ALARMn
Figure 20.1. SmaRTClock Block Diagram
188
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C8051F91x-C8051F90x
20.1. SmaRTClock Interface
The SmaRTClock Interface consists of three registers: RTC0KEY, RTC0ADR, and RTC0DAT. These interface registers are located on the CIP-51's SFR map and provide access to the SmaRTClock internal registers listed in Table 20.1. The SmaRTClock internal registers can only be accessed indirectly through the SmaRTClock Interface.
Table 20.1. SmaRTClock Internal Registers
SmaRTClock SmaRTClock Address Register 0x00-0x03 0x04 0x05 CAPTUREn RTC0CN RTC0XCN Register Name SmaRTClock Capture Registers SmaRTClock Control Register SmaRTClock Oscillator Control Register Description Four Registers used for setting the 32-bit SmaRTClock timer or reading its current value. Controls the operation of the SmaRTClock State Machine. Controls the operation of the SmaRTClock Oscillator.
Note: Some bits in this register are only available on `F912 and `F902 devices.
0x06
RTC0XCF
SmaRTClock Oscillator Configuration Register SmaRTClock Pin Configuration Register
Controls the value of the progammable oscillator load capacitance and enables/disables AutoStep. Forces XTAL3 and XTAL4 to be internally shorted.
Note: This register also contains other reserved bits which should not be modified.
0x07
RTC0PIN
0x08-0x0B
ALARMn
SmaRTClock Alarm Registers
Four registers used for setting or reading the 32-bit SmaRTClock alarm value.
20.1.1. SmaRTClock Lock and Key Functions
The SmaRTClock Interface is protected with a lock and key function. The SmaRTClock Lock and Key Register (RTC0KEY) must be written with the correct key codes, in sequence, before writes and reads to RTC0ADR and RTC0DAT may be performed. The key codes are: 0xA5, 0xF1. There are no timing restrictions, but the key codes must be written in order. If the key codes are written out of order, the wrong codes are written, or an indirect register read or write is attempted while the interface is locked, the SmaRTClock interface will be disabled, and the RTC0ADR and RTC0DAT registers will become inaccessible until the next system reset. Once the SmaRTClock interface is unlocked, software may perform any number of accesses to the SmaRTClock registers until the interface is re-locked or the device is reset. Any write to RTC0KEY while the SmaRTClock interface is unlocked will re-lock the interface. Reading the RTC0KEY register at any time will provide the SmaRTClock Interface status and will not interfere with the sequence that is being written. The RTC0KEY register description in SFR Definition 20.1 lists the definition of each status code.
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20.1.2. Using RTC0ADR and RTC0DAT to Access SmaRTClock Internal Registers
The SmaRTClock internal registers can be read and written using RTC0ADR and RTC0DAT. The RTC0ADR register selects the SmaRTClock internal register that will be targeted by subsequent reads or writes. Recommended instruction timing is provided in this section. If the recommended instruction timing is not followed, then BUSY (RTC0ADR.7) should be checked prior to each read or write operation to make sure the SmaRTClock Interface is not busy performing the previous read or write operation. A SmaRTClock Write operation is initiated by writing to the RTC0DAT register. Below is an example of writing to a SmaRTClock internal register. 1. Poll BUSY (RTC0ADR.7) until it returns 0 or follow recommended instruction timing. 2. Write 0x05 to RTC0ADR. This selects the internal RTC0CN register at SmaRTClock Address 0x05. 3. Write 0x00 to RTC0DAT. This operation writes 0x00 to the internal RTC0CN register. A SmaRTClock Read operation is initiated by setting the SmaRTClock Interface Busy bit. This transfers the contents of the internal register selected by RTC0ADR to RTC0DAT. The transferred data will remain in RTC0DAT until the next read or write operation. Below is an example of reading a SmaRTClock internal register. 1. Poll BUSY (RTC0ADR.7) until it returns 0 or follow recommended instruction timing. 2. Write 0x05 to RTC0ADR. This selects the internal RTC0CN register at SmaRTClock Address 0x05. 3. Write 1 to BUSY. This initiates the transfer of data from RTC0CN to RTC0DAT. 4. Poll BUSY (RTC0ADR.7) until it returns 0 or follow recommend instruction timing. 5. Read data from RTC0DAT. This data is a copy of the RTC0CN register.
Note: The RTC0ADR and RTC0DAT registers will retain their state upon a device reset.
20.1.3. RTC0ADR Short Strobe Feature
Reads and writes to indirect SmaRTClock registers normally take 7 system clock cycles. To minimize the indirect register access time, the Short Strobe feature decreases the read and write access time to 6 system clocks. The Short Strobe feature is automatically enabled on reset and can be manually enabled/disabled using the SHORT (RTC0ADR.4) control bit. Recommended Instruction Timing for a single register read with short strobe enabled: mov RTC0ADR, #095h nop nop nop mov A, RTC0DAT Recommended Instruction Timing for a single register write with short strobe enabled: mov RTC0ADR, #095h mov RTC0DAT, #000h nop
20.1.4. SmaRTClock Interface Autoread Feature
When Autoread is enabled, each read from RTC0DAT initiates the next indirect read operation on the SmaRTClock internal register selected by RTC0ADR. Software should set the BUSY bit once at the beginning of each series of consecutive reads. Software should follow recommended instruction timing or check if the SmaRTClock Interface is busy prior to reading RTC0DAT. Autoread is enabled by setting AUTORD (RTC0ADR.6) to logic 1.
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20.1.5. RTC0ADR Autoincrement Feature
For ease of reading and writing the 32-bit CAPTURE and ALARM values, RTC0ADR automatically increments after each read or write to a CAPTUREn or ALARMn register. This speeds up the process of setting an alarm or reading the current SmaRTClock timer value. Autoincrement is always enabled. Recommended Instruction Timing for a multi-byte register read with short strobe and auto read enabled: mov nop nop nop mov nop nop mov nop nop mov nop nop mov RTC0ADR, #0d0h
A, RTC0DAT
A, RTC0DAT
A, RTC0DAT
A, RTC0DAT
Recommended Instruction Timing for a multi-byte register write with short strobe enabled: mov mov nop mov nop mov nop mov nop RTC0ADR, #010h RTC0DAT, #05h RTC0DAT, #06h RTC0DAT, #07h RTC0DAT, #08h
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C8051F91x-C8051F90x
SFR Definition 20.1. RTC0KEY: SmaRTClock Lock and Key
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
RTC0ST[7:0] R/W 0 0 0 0
SFR Page = 0x0; SFR Address = 0xAE Bit Name 7:0 RTC0ST
Function
SmaRTClock Interface Lock/Key and Status. Locks/unlocks the SmaRTClock interface when written. Provides lock status when read. Read: 0x00: SmaRTClock Interface is locked. 0x01: SmaRTClock Interface is locked. First key code (0xA5) has been written, waiting for second key code. 0x02: SmaRTClock Interface is unlocked. First and second key codes (0xA5, 0xF1) have been written. 0x03: SmaRTClock Interface is disabled until the next system reset. Write: When RTC0ST = 0x00 (locked), writing 0xA5 followed by 0xF1 unlocks the SmaRTClock Interface. When RTC0ST = 0x01 (waiting for second key code), writing any value other than the second key code (0xF1) will change RTC0STATE to 0x03 and disable the SmaRTClock Interface until the next system reset. When RTC0ST = 0x02 (unlocked), any write to RTC0KEY will lock the SmaRTClock Interface. When RTC0ST = 0x03 (disabled), writes to RTC0KEY have no effect.
192
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SFR Definition 20.2. RTC0ADR: SmaRTClock Address
Bit Name Type Reset 7 BUSY R/W 0 6 AUTORD R/W 0 R 0 5 4 SHORT R/W 0 0 0 3 2 ADDR[3:0] R/W 0 0 1 0
SFR Page = 0x0; SFR Address = 0xAC Bit Name 7 6 BUSY
Function
SmaRTClock Interface Busy Indicator. Indicates SmaRTClock interface status. Writing 1 to this bit initiates an indirect read.
AUTORD SmaRTClock Interface Autoread Enable. Enables/disables Autoread. 0: Autoread Disabled. 1: Autoread Enabled. Unused SHORT Unused. Read = 0b; Write = Don't Care. Short Strobe Enable. Enables/disables the Short Strobe Feature. 0: Short Strobe disabled. 1: Short Strobe enabled.
5 4
3:0
ADDR[3:0] SmaRTClock Indirect Register Address. Sets the currently selected SmaRTClock register. See Table 20.1 for a listing of all SmaRTClock indirect registers.
Note: The ADDR bits increment after each indirect read/write operation that targets a CAPTUREn or ALARMn internal SmaRTClock register.
SFR Definition 20.3. RTC0DAT: SmaRTClock Data
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
RTC0DAT[7:0] R/W 0 0 0 0
SFR Page= 0x0; SFR Address = 0xAD Bit Name 7:0
Function
RTC0DAT SmaRTClock Data Bits. Holds data transferred to/from the internal SmaRTClock register selected by RTC0ADR.
Note: Read-modify-write instructions (orl, anl, etc.) should not be used on this register.
Rev. 1.0
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20.2. SmaRTClock Clocking Sources
The SmaRTClock peripheral is clocked from its own timebase, independent of the system clock. The SmaRTClock timebase can be derived from an external CMOS clock, the internal LFO (`F912 and `F902 devices only), or the SmaRTClock oscillator circuit, which has two modes of operation: Crystal Mode, and Self-Oscillate Mode. The oscillation frequency is 32.768 kHz in Crystal Mode and can be programmed in the range of 10 kHz to 40 kHz in Self-Oscillate Mode. The internal LFO frequency is 16.4 kHz 20%. The frequency of the SmaRTClock oscillator can be measured with respect to another oscillator using an onchip timer. See Section "25. Timers" on page 270 for more information on how this can be accomplished.
Note: The SmaRTClock timebase can be selected as the system clock and routed to a port pin. See Section "19. Clocking Sources" on page 179 for information on selecting the system clock source and Section "21. Port Input/Output" on page 205 for information on how to route the system clock to a port pin. On `F912 and `F902 devices, the SmaRTClock timebase can be routed to a port pin while the device is in its ultra low power sleep mode. See the PMU0MD register description for details.
20.2.1. Using the SmaRTClock Oscillator with a Crystal or External CMOS Clock
When using Crystal Mode, a 32.768 kHz crystal should be connected between XTAL3 and XTAL4. No other external components are required. The following steps show how to start the SmaRTClock crystal oscillator in software: 1. Set SmaRTClock to Crystal Mode (XMODE = 1). 2. Disable Automatic Gain Control (AGCEN) and enable Bias Doubling (BIASX2) for fast crystal startup. 3. Set the desired loading capacitance (RTC0XCF). 4. Enable power to the SmaRTClock oscillator circuit (RTC0EN = 1). 5. Wait 20 ms. 6. Poll the SmaRTClock Clock Valid Bit (CLKVLD) until the crystal oscillator stabilizes. 7. Poll the SmaRTClock Load Capacitance Ready Bit (LOADRDY) until the load capacitance reaches its programmed value. 8. Enable Automatic Gain Control (AGCEN) and disable Bias Doubling (BIASX2) for maximum power savings. 9. Enable the SmaRTClock missing clock detector. 10. Wait 2 ms. 11. Clear the PMU0CF wake-up source flags. In Crystal Mode, the SmaRTClock oscillator may be driven by an external CMOS clock. The CMOS clock should be applied to XTAL3. XTAL4 should be left floating. The input low voltage (VIL) and input high voltage (VIH) for XTAL3 when used with an external CMOS clock are 0.1 and 0.8 V, respectively. The SmaRTClock oscillator should be configured to its lowest bias setting with AGC disabled. The CLKVLD bit is indeterminate when using a CMOS clock, however, the OSCFAIL bit may be checked 2 ms after SmaRTClock oscillator is powered on to ensure that there is a valid clock on XTAL3.
194
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20.2.2. Using the SmaRTClock Oscillator in Self-Oscillate Mode
When using Self-Oscillate Mode, the XTAL3 and XTAL4 pins should be shorted together. The RTC0PIN register can be used to internally short XTAL3 and XTAL4. The following steps show how to configure SmaRTClock for use in Self-Oscillate Mode: 1. Set SmaRTClock to Self-Oscillate Mode (XMODE = 0). 2. Set the desired oscillation frequency: For oscillation at about 20 kHz, set BIASX2 = 0. For oscillation at about 40 kHz, set BIASX2 = 1. 3. The oscillator starts oscillating instantaneously. 4. Fine tune the oscillation frequency by adjusting the load capacitance (RTC0XCF).
20.2.3. Using the Low Frequency Oscillator (LFO)
The low frequency oscillator provides an ultra low power, on-chip clock source to the SmaRTClock. The typical frequency of oscillation is 16.4 kHz 20%. No external components are required to use the LFO and the XTAL3 and XTAL4 pins do not need to be shorted together. The LFO is only available on `F912 and `F902 devices. The following steps show how to configure SmaRTClock for use with the LFO: 1. Enable and select the Low Frequency Oscillator (LFOEN = 1). 2. The LFO starts oscillating instantaneously. When the LFO is enabled, the SmaRTClock oscillator increments bit 1 of the 32-bit timer (instead of bit 0). This effectively multiplies the LFO frequency by 2, making the RTC timebase behave as if a 32.768 kHz crystal is connected at the output.
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20.2.4. Programmable Load Capacitance
The programmable load capacitance has 16 values to support crystal oscillators with a wide range of recommended load capacitance. If Automatic Load Capacitance Stepping is enabled, the crystal load capacitors start at the smallest setting to allow a fast startup time, then slowly increase the capacitance until the final programmed value is reached. The final programmed loading capacitor value is specified using the LOADCAP bits in the RTC0XCF register. The LOADCAP setting specifies the amount of on-chip load capacitance and does not include any stray PCB capacitance. Once the final programmed loading capacitor value is reached, the LOADRDY flag will be set by hardware to logic 1. When using the SmaRTClock oscillator in Self-Oscillate mode, the programmable load capacitance can be used to fine tune the oscillation frequency. In most cases, increasing the load capacitor value will result in a decrease in oscillation frequency.Table 20.2 shows the crystal load capacitance for various settings of LOADCAP.
Table 20.2. SmaRTClock Load Capacitance Settings
LOADCAP 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111 Crystal Load Capacitance 4.0 pF 4.5 pF 5.0 pF 5.5 pF 6.0 pF 6.5 pF 7.0 pF 7.5 pF 8.0 pF 8.5 pF 9.0 pF 9.5 pF 10.5 pF 11.5 pF 12.5 pF 13.5 pF Equivalent Capacitance seen on XTAL3 and XTAL4 8.0 pF 9.0 pF 10.0 pF 11.0 pF 12.0 pF 13.0 pF 14.0 pF 15.0 pF 16.0 pF 17.0 pF 18.0 pF 19.0 pF 21.0 pF 23.0 pF 25.0 pF 27.0 pF
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20.2.5. Automatic Gain Control (Crystal Mode Only) and SmaRTClock Bias Doubling
Automatic Gain Control allows the SmaRTClock oscillator to trim the oscillation amplitude of a crystal in order to achieve the lowest possible power consumption. Automatic Gain Control automatically detects when the oscillation amplitude has reached a point where it safe to reduce the drive current, therefore, it may be enabled during crystal startup. It is recommended to enable Automatic Gain Control in most systems which use the SmaRTClock oscillator in Crystal Mode. The following are recommended crystal specifications and operating conditions when Automatic Gain Control is enabled: * ESR < 50 k * Load Capacitance < 10 pF * Supply Voltage < 3.0 V * Temperature > -20 C When using Automatic Gain Control, it is recommended to perform an oscillation robustness test to ensure that the chosen crystal will oscillate under the worst case condition to which the system will be exposed. The worst case condition that should result in the least robust oscillation is at the following system conditions: lowest temperature, highest supply voltage, highest ESR, highest load capacitance, and lowest bias current (AGC enabled, Bias Double Disabled). To perform the oscillation robustness test, the SmaRTClock oscillator should be enabled and selected as the system clock source. Next, the SYSCLK signal should be routed to a port pin configured as a push-pull digital output. The positive duty cycle of the output clock can be used as an indicator of oscillation robustness. As shown in Figure 20.2, duty cycles less than 55% indicate a robust oscillation. As the duty cycle approaches 60%, oscillation becomes less reliable and the risk of clock failure increases. Increasing the bias current (by disabling AGC) will always improve oscillation robustness and will reduce the output clock's duty cycle. This test should be performed at the worst case system conditions, as results at very low temperatures or high supply voltage will vary from results taken at room temperature or low supply voltage.
Safe Operating Zone
Low Risk of Clock Failure
High Risk of Clock Failure
25%
55%
60%
Duty Cycle
Figure 20.2. Interpreting Oscillation Robustness (Duty Cycle) Test Results
As an alternative to performing the oscillation robustness test, Automatic Gain Control may be disabled at the cost of increased power consumption (approximately 200 nA). Disabling Automatic Gain Control will provide the crystal oscillator with higher immunity against external factors which may lead to clock failure. Automatic Gain Control must be disabled if using the SmaRTClock oscillator in self-oscillate mode. Table 20.3 shows a summary of the oscillator bias settings. The SmaRTClock Bias Doubling feature allows the self-oscillation frequency to be increased (almost doubled) and allows a higher crystal drive strength in crystal mode. High crystal drive strength is recommended when the crystal is exposed to poor environmental conditions such as excessive moisture. SmaRTClock Bias Doubling is enabled by setting BIASX2 (RTC0XCN.5) to 1.
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.
Table 20.3. SmaRTClock Bias Settings
Mode Crystal Setting Bias Double Off, AGC On Bias Double Off, AGC Off Bias Double On, AGC On Bias Double On, AGC Off Self-Oscillate Bias Double Off Bias Double On Power Consumption Lowest 600 nA Low 800 nA High Highest Low High
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20.2.6. Missing SmaRTClock Detector
The missing SmaRTClock detector is a one-shot circuit enabled by setting MCLKEN (RTC0CN.6) to 1. When the SmaRTClock Missing Clock Detector is enabled, OSCFAIL (RTC0CN.5) is set by hardware if SmaRTClock oscillator remains high or low for more than 100 s. A SmaRTClock Missing Clock detector timeout can trigger an interrupt, wake the device from a low power mode, or reset the device. See Section "12. Interrupt Handler" on page 120, Section "14. Power Management" on page 143, and Section "18. Reset Sources" on page 171 for more information.
Note: The SmaRTClock Missing Clock Detector should be disabled when making changes to the oscillator settings in RTC0XCN.
20.2.7. SmaRTClock Oscillator Crystal Valid Detector
The SmaRTClock oscillator crystal valid detector is an oscillation amplitude detector circuit used during crystal startup to determine when oscillation has started and is nearly stable. The output of this detector can be read from the CLKVLD bit (RTX0XCN.4).
Notes: * The CLKVLD bit has a blanking interval of 2 ms. During the first 2 ms after turning on the crystal oscillator, the output of CLKVLD is not valid. * This SmaRTClock crystal valid detector (CLKVLD) is not intended for detecting an oscillator failure. The missing SmaRTClock detector (CLKFAIL) should be used for this purpose.
20.3. SmaRTClock Timer and Alarm Function
The SmaRTClock timer is a 32-bit counter that, when running (RTC0TR = 1), is incremented every SmaRTClock oscillator cycle. The timer has an alarm function that can be set to generate an interrupt, wake the device from a low power mode, or reset the device at a specific time. See Section "12. Interrupt Handler" on page 120, Section "14. Power Management" on page 143, and Section "18. Reset Sources" on page 171 for more information. The SmaRTClock timer includes an Auto Reset feature, which automatically resets the timer to zero one SmaRTClock cycle after an alarm occurs. When using Auto Reset, the Alarm match value should always be set to 1 count less than the desired match value. Auto Reset can be enabled by writing a 1 to ALRM (RTC0CN.2).
20.3.1. Setting and Reading the SmaRTClock Timer Value
The 32-bit SmaRTClock timer can be set or read using the six CAPTUREn internal registers. Note that the timer does not need to be stopped before reading or setting its value. The following steps can be used to set the timer value: 1. Write the desired 32-bit set value to the CAPTUREn registers. 2. Write 1 to RTC0SET. This will transfer the contents of the CAPTUREn registers to the SmaRTClock timer. 3. Operation is complete when RTC0SET is cleared to 0 by hardware. The following steps can be used to read the current timer value: 1. Write 1 to RTC0CAP. This will transfer the contents of the timer to the CAPTUREn registers. 2. Poll RTC0CAP until it is cleared to 0 by hardware. 3. A snapshot of the timer value can be read from the CAPTUREn registers
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20.3.2. Setting a SmaRTClock Alarm
The SmaRTClock alarm function compares the 32-bit value of SmaRTClock Timer to the value of the ALARMn registers. An alarm event is triggered if the SmaRTClock timer is equal to the ALARMn registers. If Auto Reset is enabled, the 32-bit timer will be cleared to zero one SmaRTClock cycle after the alarm event. The SmaRTClock alarm event can be configured to reset the MCU, wake it up from a low power mode, or generate an interrupt. See Section "12. Interrupt Handler" on page 120, Section "14. Power Management" on page 143, and Section "18. Reset Sources" on page 171 for more information. The following steps can be used to set up a SmaRTClock Alarm: 1. Disable SmaRTClock Alarm Events (RTC0AEN = 0). 2. Set the ALARMn registers to the desired value. 3. Enable SmaRTClock Alarm Events (RTC0AEN = 1).
Notes: * The ALRM bit, which is used as the SmaRTClock Alarm Event flag, is cleared by disabling SmaRTClock Alarm Events (RTC0AEN = 0). * If AutoReset is disabled, disabling (RTC0AEN = 0) then Re-enabling Alarm Events (RTC0AEN = 1) after a SmaRTClock Alarm without modifying ALARMn registers will automatically schedule the next alarm after 2^32 SmaRTClock cycles (approximately 36 hours using a 32.768 kHz crystal). * The SmaRTClock Alarm Event flag will remain asserted for a maximum of one SmaRTClock cycle. See Section "14. Power Management" on page 143 for information on how to capture a SmaRTClock Alarm event using a flag which is not automatically cleared by hardware.
20.3.3. Software Considerations for using the SmaRTClock Timer and Alarm
The SmaRTClock timer and alarm have two operating modes to suit varying applications. The two modes are described below: Mode 1: The first mode uses the SmaRTClock timer as a perpetual timebase which is never reset to zero. Every 36 hours, the timer is allowed to overflow without being stopped or disrupted. The alarm interval is software managed and is added to the ALRMn registers by software after each alarm. This allows the alarm match value to always stay ahead of the timer by one software managed interval. If software uses 32-bit unsigned addition to increment the alarm match value, then it does not need to handle overflows since both the timer and the alarm match value will overflow in the same manner. This mode is ideal for applications which have a long alarm interval (e.g., 24 or 36 hours) and/or have a need for a perpetual timebase. An example of an application that needs a perpetual timebase is one whose wake-up interval is constantly changing. For these applications, software can keep track of the number of timer overflows in a 16-bit variable, extending the 32-bit (36 hour) timer to a 48-bit (272 year) perpetual timebase. Mode 2: The second mode uses the SmaRTClock timer as a general purpose up counter which is auto reset to zero by hardware after each alarm. The alarm interval is managed by hardware and stored in the ALRMn registers. Software only needs to set the alarm interval once during device initialization. After each alarm, software should keep a count of the number of alarms that have occurred in order to keep track of time. This mode is ideal for applications that require minimal software intervention and/or have a fixed alarm interval. This mode is the most power efficient since it requires less CPU time per alarm.
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Internal Register Definition 20.4. RTC0CN: SmaRTClock Control
Bit Name Type Reset 7 RTC0EN R/W 0 6 MCLKEN R/W 0 5 OSCFAIL R/W Varies 4 RTC0TR R/W 0 3 RTC0AEN R/W 0 Function 2 ALRM R/W 0 1 R/W 0 0 R/W 0
RTC0SET RTC0CAP
SmaRTClock Address = 0x04 Bit Name 7 RTC0EN
SmaRTClock Enable. Enables/disables the SmaRTClock oscillator and associated bias currents. 0: SmaRTClock oscillator disabled. 1: SmaRTClock oscillator enabled.
6
MCLKEN Missing SmaRTClock Detector Enable. Enables/disables the missing SmaRTClock detector. 0: Missing SmaRTClock detector disabled. 1: Missing SmaRTClock detector enabled. OSCFAIL SmaRTClock Oscillator Fail Event Flag. Set by hardware when a missing SmaRTClock detector timeout occurs. Must be cleared by software. The value of this bit is not defined when the SmaRTClock oscillator is disabled. RTC0TR SmaRTClock Timer Run Control. Controls if the SmaRTClock timer is running or stopped (holds current value). 0: SmaRTClock timer is stopped. 1: SmaRTClock timer is running.
5
4
3
RTC0AEN SmaRTClock Alarm Enable. Enables/disables the SmaRTClock alarm function. Also clears the ALRM flag. 0: SmaRTClock alarm disabled. 1: SmaRTClock alarm enabled. ALRM SmaRTClock Alarm Event Flag and Auto Reset Enable. Reads return the state of the alarm event flag. Writes enable/disable the Auto Reset function. Read: 0: SmaRTClock alarm event flag is de-asserted. 1: SmaRTClock alarm event flag is asserted. Write: 0: Disable Auto Reset. 1: Enable Auto Reset.
2
1
RTC0SET SmaRTClock Timer Set. Writing 1 initiates a SmaRTClock timer set operation. This bit is cleared to 0 by hardware to indicate that the timer set operation is complete. RTC0CAP SmaRTClock Timer Capture. Writing 1 initiates a SmaRTClock timer capture operation. This bit is cleared to 0 by hardware to indicate that the timer capture operation is complete.
0
Note: The ALRM flag will remain asserted for a maximum of one SmaRTClock cycle. See Section "Power Management" on page 143 for information on how to capture a SmaRTClock Alarm event using a flag which is not automatically cleared by hardware.
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Internal Register Definition 20.5. RTC0XCN: SmaRTClock Oscillator Control
Bit Name Type Reset 7 AGCEN R/W 0 6 XMODE R/W 0 5 BIASX2 R/W 0 4 CLKVLD R 0 3 LFOEN R 0 R 0 R 0 R 0 2 1 0
SmaRTClock Address = 0x05 Bit Name 7 AGCEN
Function
SmaRTClock Oscillator Automatic Gain Control (AGC) Enable. 0: AGC disabled. 1: AGC enabled. SmaRTClock Oscillator Mode. Selects Crystal or Self Oscillate Mode. 0: Self-Oscillate Mode selected. 1: Crystal Mode selected. SmaRTClock Oscillator Bias Double Enable. Enables/disables the Bias Double feature. 0: Bias Double disabled. 1: Bias Double enabled. SmaRTClock Oscillator Crystal Valid Indicator. Indicates if oscillation amplitude is sufficient for maintaining oscillation. 0: Oscillation has not started or oscillation amplitude is too low to maintain oscillation. 1: Sufficient oscillation amplitude detected. Low Frequency Oscillator Enable and Select. Overrides XMODE and selects the internal low frequency oscillator (LFO) as the SmaRTClock oscillator source. Only available on `F912 and `F902 devices. 0: XMODE determines SmaRTClock oscillator source. 1: LFO enabled and selected as SmaRTClock oscillator source. Unused. Read = 000b; Write = Don't Care.
6
XMODE
5
BIASX2
4
CLKVLD
3
LFOEN
2:0
Unused
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Internal Register Definition 20.6. RTC0XCF: SmaRTClock Oscillator Configuration
Bit 7 6 LOADRDY R 0 R 0 R 0 Varies Varies 5 4 3 2 1 0
Name AUTOSTP Type Reset R/W 0
LOADCAP R/W Varies Varies
SmaRTClock Address = 0x06 Bit Name 7 AUTOSTP
Function
Automatic Load Capacitance Stepping Enable. Enables/disables automatic load capacitance stepping. 0: Load capacitance stepping disabled. 1: Load capacitance stepping enabled. Load Capacitance Ready Indicator. Set by hardware when the load capacitance matches the programmed value. 0: Load capacitance is currently stepping. 1: Load capacitance has reached it programmed value. Unused. Read = 00b; Write = Don't Care. Load Capacitance Programmed Value. Holds the user's desired value of the load capacitance. See Table 20.2 on page 196.
6
LOADRDY
5:4 3:0
Unused LOADCAP
Internal Register Definition 20.7. RTC0PIN: SmaRTClock Pin Configuration
Bit Name Type Reset 7 RTC0PIN W 0 R/W Varies R/W Varies R/W Varies R/W Varies R/W Varies R/W Varies R/W Varies 6 5 4 3 2 1 0
SmaRTClock Address = 0x07 Bit Name 7 RTC0PIN SmaRTClock Pin Configuration.
Function
0: XTAL3 and XTAL4 in their normal configuration. 1: XTAL3 and XTAL4 internally shorted for use with Self Oscillate Mode. 6:0 Reserved Reserved. Read = Varies. Software should not modify the value of these bits. To change the RTC0PIN setting, the entire register contents should be read, modified, then rewritten.
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Internal Register Definition 20.8. CAPTUREn: SmaRTClock Timer Capture
Bit Name Type Reset R/W 0 R/W 0 R/W 0 7 6 5 4 3 2 1 0
CAPTURE[31:0] R/W 0 R/W 0 R/W 0 R/W 0 R/W 0
SmaRTClock Addresses: CAPTURE0 = 0x00; CAPTURE1 = 0x01; CAPTURE2 =0x02; CAPTURE3: 0x03. Bit Name Function 7:0 CAPTURE[31:0] SmaRTClock Timer Capture. These 4 registers (CAPTURE3-CAPTURE0) are used to read or set the 32-bit SmaRTClock timer. Data is transferred to or from the SmaRTClock timer when the RTC0SET or RTC0CAP bits are set.
Note: The least significant bit of the timer capture value is in CAPTURE0.0.
Internal Register Definition 20.9. ALARMn: SmaRTClock Alarm Programmed Value
Bit Name Type Reset R/W 0 R/W 0 R/W 0 7 6 5 4 3 2 1 0
ALARM[31:0] R/W 0 R/W 0 R/W 0 R/W 0 R/W 0
SmaRTClock Addresses: ALARM0 = 0x08; ALARM1 = 0x09; ALARM2 = 0x0A; ALARM3 = 0x0B Bit Name Function 7:0 ALARM[31:0] SmaRTClock Alarm Programmed Value. These 4 registers (ALARM3-ALARM0) are used to set an alarm event for the SmaRTClock timer. The SmaRTClock alarm should be disabled (RTC0AEN=0) when updating these registers.
Note: The least significant bit of the alarm programmed value is in ALARM0.0.
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21. Port Input/Output
Digital and analog resources are available through 16 I/O pins. Port pins are organized as three byte-wide ports. Port pins P0.0-P1.6 can be defined as digital or analog I/O. Digital I/O pins can be assigned to one of the internal digital resources or used as general purpose I/O (GPIO). Analog I/O pins are used by the internal analog resources. P2.7 can be used as GPIO and is shared with the C2 Interface Data signal (C2D). See Section "27. C2 Interface" on page 312 for more details. The designer has complete control over which digital and analog functions are assigned to individual Port pins, limited only by the number of physical I/O pins. This resource assignment flexibility is achieved through the use of a Priority Crossbar Decoder. See Section 21.3 for more information on the Crossbar. All Port I/Os are 5 V tolerant when used as digital inputs or open-drain outputs. For Port I/Os configured as push-pull outputs, current is sourced from the VDD/DC+ supply. Port I/Os used for analog functions can operate up to the VDD/DC+ supply voltage. See Section 21.1 for more information on Port I/O operating modes and the electrical specifications chapter for detailed electrical specifications.
XBR0, XBR1, XBR2, PnSKIP Registers
Port Match P0MASK, P0MAT P1MASK, P1MAT
Priority Decoder
2 4 2 SMBus CP0 CP1 Outputs SYSCLK PCA Lowest Priority 7 2 8 P0 (Port Latches) 1 (P0.0-P0.7) 7 P1 (P1.0-P1.6) 1 P2 (P2.7) To Analog Peripherals (ADC0, CP0, and CP1 inputs, VREF, IREF0, AGND) P2 I/O Cell 4
External Interrupts EX0 and EX1 PnMDOUT, PnMDIN Registers
Highest Priority
UART SPI0 SPI1
(Internal Digital Signals)
P0.0
Digital Crossbar
8
P0 I/O Cells P0.7 P1.0 P1 I/O Cells P1.6
7
T0, T1
P2.7
Figure 21.1. Port I/O Functional Block Diagram
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21.1. Port I/O Modes of Operation
Port pins P0.0-P1.6 use the Port I/O cell shown in Figure 21.2. Each Port I/O cell can be configured by software for analog I/O or digital I/O using the PnMDIN registers. On reset, all Port I/O cells default to a digital high impedance state with weak pull-ups enabled.
21.1.1. Port Pins Configured for Analog I/O
Any pins to be used as Comparator or ADC input, external oscillator input/output, or AGND, VREF, or Current Reference output should be configured for analog I/O (PnMDIN.n = 0). When a pin is configured for analog I/O, its weak pullup and digital receiver are disabled. In most cases, software should also disable the digital output drivers. Port pins configured for analog I/O will always read back a value of 0 regardless of the actual voltage on the pin. Configuring pins as analog I/O saves power and isolates the Port pin from digital interference. Port pins configured as digital inputs may still be used by analog peripherals; however, this practice is not recommended and may result in measurement errors.
21.1.2. Port Pins Configured For Digital I/O
Any pins to be used by digital peripherals (UART, SPI, SMBus, etc.), external digital event capture functions, or as GPIO should be configured as digital I/O (PnMDIN.n = 1). For digital I/O pins, one of two output modes (push-pull or open-drain) must be selected using the PnMDOUT registers. Push-pull outputs (PnMDOUT.n = 1) drive the Port pad to the VDD/DC+ or GND supply rails based on the output logic value of the Port pin. Open-drain outputs have the high side driver disabled; therefore, they only drive the Port pad to GND when the output logic value is 0 and become high impedance inputs (both high and low drivers turned off) when the output logic value is 1. When a digital I/O cell is placed in the high impedance state, a weak pull-up transistor pulls the Port pad to the VDD/DC+ supply voltage to ensure the digital input is at a defined logic state. Weak pull-ups are disabled when the I/O cell is driven to GND to minimize power consumption and may be globally disabled by setting WEAKPUD to 1. The user must ensure that digital I/O are always internally or externally pulled or driven to a valid logic state. Port pins configured for digital I/O always read back the logic state of the Port pad, regardless of the output logic value of the Port pin.
WEAKPUD (Weak Pull-Up Disable) PnMDOUT.x (1 for push-pull) (0 for open-drain) XBARE (Crossbar Enable) Pn.x - Output Logic Value (Port Latch or Crossbar) PnMDIN.x (1 for digital) (0 for analog) To/From Analog Peripheral Pn.x - Input Logic Value (Reads 0 when pin is configured as an analog I/O) GND VDD/DC+
VDD/DC+
(WEAK) PORT PAD
Figure 21.2. Port I/O Cell Block Diagram
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21.1.3. Interfacing Port I/O to 5 V and 3.3 V Logic
All Port I/O configured for digital, open-drain operation are capable of interfacing to digital logic operating at a supply voltage higher than 4.5 V and less than 5.25 V. When the supply voltage is in the range of 1.8 to 2.2 V, the I/O may also interface to digital logic operating between 3.0 to 3.6 V if the input signal frequency is less than 12.5 MHz or less than 25 MHz if the signal rise time (10% to 90%) is less than 1.2 ns. When operating at a supply voltage above 2.2 V, the device should not interface to 3.3 V logic; however, interfacing to 5 V logic is permitted. An external pull-up resistor to the higher supply voltage is typically required for most systems. Important Note:
When interfacing to a signal that is between 4.5 and 5.25 V, the maximum clock frequency that may be input on a GPIO pin is 12.5 MHz. The exception to this rule is when routing an external CMOS clock to P0.3, in which case, a signal up to 25 MHz is valid as long as the rise time (10% to 90%) is shorter than 1.8 ns. When the supply voltage is less than 2.2 V and interfacing to a signal that is between 3.0 and 3.6 V, the maximum clock frequency that may be input on a GPIO pin is 3.125 MHz. The exception to this rule is when routing an external CMOS clock to P0.3, in which case, a signal up to 25 MHz is valid as long as the rise time (10% to 90%) is shorter than 1.2 ns. In a multi-voltage interface, the external pull-up resistor should be sized to allow a current of at least 150 A to flow into the Port pin when the supply voltage is between (VDD/DC+ plus 0.4 V) and (VDD/DC+ plus 1.0 V). Once the Port pad voltage increases beyond this range, the current flowing into the Port pin is minimal. These guidelines only apply to multi-voltage interfaces. Port I/Os may always interface to digital logic operating at the same supply voltage.
21.1.4. Increasing Port I/O Drive Strength
Port I/O output drivers support a high and low drive strength; the default is low drive strength. The drive strength of a Port I/O can be configured using the PnDRV registers. See Section "4. Electrical Characteristics" on page 36 for the difference in output drive strength between the two modes.
21.2. Assigning Port I/O Pins to Analog and Digital Functions
Port I/O pins P0.0-P1.6 can be assigned to various analog, digital, and external interrupt functions. The Port pins assuaged to analog functions should be configured for analog I/O and Port pins assuaged to digital or external interrupt functions should be configured for digital I/O.
21.2.1. Assigning Port I/O Pins to Analog Functions
Table 21.1 shows all available analog functions that need Port I/O assignments. Port pins selected for these analog functions should have their digital drivers disabled (PnMDOUT.n = 0 and Port Latch = 1) and their corresponding bit in PnSKIP set to 1. This reserves the pin for use by the analog function and does not allow it to be claimed by the Crossbar. Table 21.1 shows the potential mapping of Port I/O to each analog function.
Table 21.1. Port I/O Assignment for Analog Functions
Analog Function ADC Input Comparator0 Input Comparator1 Input Potentially Assignable Port Pins P0.0-P1.6 P0.0-P1.6 P0.0-P1.6 SFR(s) used for Assignment ADC0MX, PnSKIP CPT0MX, PnSKIP CPT1MX, PnSKIP
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Table 21.1. Port I/O Assignment for Analog Functions
Analog Function Voltage Reference (VREF0) Analog Ground Reference (AGND) Current Reference (IREF0) External Oscillator Input (XTAL1) External Oscillator Output (XTAL2) Potentially Assignable Port Pins P0.0 P0.1 P0.7 P0.2 P0.3 SFR(s) used for Assignment REF0CN, PnSKIP REF0CN, PnSKIP IREF0CN, PnSKIP OSCXCN, PnSKIP OSCXCN, PnSKIP
21.2.2. Assigning Port I/O Pins to Digital Functions
Any Port pins not assigned to analog functions may be assigned to digital functions or used as GPIO. Most digital functions rely on the Crossbar for pin assignment; however, some digital functions bypass the Crossbar in a manner similar to the analog functions listed above. Port pins used by these digital functions and any Port pins selected for use as GPIO should have their corresponding bit in PnSKIP set to 1. Table 21.2 shows all available digital functions and the potential mapping of Port I/O to each digital function.
Table 21.2. Port I/O Assignment for Digital Functions
Digital Function UART0, SPI1, SPI0, SMBus, CP0 and CP1 Outputs, System Clock Output, PCA0, Timer0 and Timer1 External Inputs. Any pin used for GPIO Potentially Assignable Port Pins Any Port pin available for assignment by the Crossbar. This includes P0.0-P1.6 pins which have their PnSKIP bit set to 0. Note: The Crossbar will always assign UART0 and SPI1 pins to fixed locations. P0.0-P1.6, P2.7 SFR(s) used for Assignment XBR0, XBR1, XBR2
P0SKIP, P1SKIP
21.2.3. Assigning Port I/O Pins to External Digital Event Capture Functions
External digital event capture functions can be used to trigger an interrupt or wake the device from a low power mode when a transition occurs on a digital I/O pin. The digital event capture functions do not require dedicated pins and will function on both GPIO pins (PnSKIP = 1) and pins in use by the Crossbar (PnSKIP = 0). External digital even capture functions cannot be used on pins configured for analog I/O. Table 21.3 shows all available external digital event capture functions.
Table 21.3. Port I/O Assignment for External Digital Event Capture Functions
Digital Function External Interrupt 0 External Interrupt 1 Port Match Potentially Assignable Port Pins P0.0-P0.7 P0.0-P0.7 P0.0-P1.6 SFR(s) used for Assignment IT01CF IT01CF P0MASK, P0MAT P1MASK, P1MAT
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21.3. Priority Crossbar Decoder
The Priority Crossbar Decoder assigns a Port I/O pin to each software selected digital function using the fixed peripheral priority order shown in Figure 21.3. The registers XBR0, XBR1, and XBR2 defined in SFR Definition 21.1, SFR Definition 21.2, and SFR Definition 21.3 are used to select digital functions in the Crossbar. The Port pins available for assignment by the Crossbar include all Port pins (P0.0-P1.6) which have their corresponding bit in PnSKIP set to 0. From Figure 21.3, the highest priority peripheral is UART0. If UART0 is selected in the Crossbar (using the XBRn registers), then P0.4 and P0.5 will be assigned to UART0. The next highest priority peripheral is SPI1. If SPI1 is selected in the Crossbar, then P1.0-P1.3 will be assigned to SPI1. The user should ensure that the pins to be assigned by the Crossbar have their PnSKIP bits set to 0. For all remaining digital functions selected in the Crossbar, starting at the top of Figure 21.3 going down, the least-significant unskipped, unassigned Port pin(s) are assigned to that function. If a Port pin is already assigned (e.g. UART0 or SPI1 pins), or if its PnSKIP bit is set to 1, then the Crossbar will skip over the pin and find next available unskipped, unassigned Port pin. All Port pins used for analog functions, GPIO, or dedicated digital functions such as the EMIF should have their PnSKIP bit set to 1. Figure 21.3 shows the Crossbar Decoder priority with no Port pins skipped (P0SKIP, P1SKIP = 0x00); Figure 21.4 shows the Crossbar Decoder priority with the External Oscillator pins (XTAL1 and XTAL2) skipped (P0SKIP = 0x0C).
Notes: * The Crossbar must be enabled (XBARE = 1) before any Port pin is used as a digital output. Port output drivers are disabled while the Crossbar is disabled. * When SMBus is selected in the Crossbar, the pins associated with SDA and SCL will automatically be forced into open-drain output mode regardless of the PnMDOUT setting. * SPI0 can be operated in either 3-wire or 4-wire modes, depending on the state of the NSSMD1-NSSMD0 bits in register SPI0CN. The NSS signal is only routed to a Port pin when 4-wire mode is selected. When SPI0 is selected in the Crossbar, the SPI0 mode (3-wire or 4-wire) will affect the pinout of all digital functions lower in priority than SPI0. * For given XBRn, PnSKIP, and SPInCN register settings, one can determine the I/O pin-out of the device using Figure 21.3 and Figure 21.4.
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P0 CNVSTR XTAL1 XTAL2 AGND IREF0 VREF P1 P2 C2D 0 1 2 3 4 5 6 7 (*4-Wire SPI Only) (*4-Wire SPI Only) 0 0 0 0 0 0 0 X P1SKIP[0:7]
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SF Signals PIN I/O TX0 RX0 SCK (SPI1) MISO (SPI1) MOSI (SPI1) NSS* (SPI1) SCK (SPI0) MISO (SPI0) MOSI (SPI0) NSS* (SPI0) SDA SCL CP0 CP0A CP1 CP1A /SYSCLK CEX0 CEX1 CEX2 CEX3 CEX4 CEX5 ECI T0 T1
0
1
2
3
4
5
6
7
0
0
0
0
0
0
0
0
P0SKIP[0:7]
Figure 21.3. Crossbar Priority Decoder with No Pins Skipped
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P0 CNVSTR XTAL1 XTAL2 AGND IREF0 VREF P1 P2 C2D 0 1 2 3 4 5 6 7 (*4-Wire SPI Only) (*4-Wire SPI Only) 0 0 0 0 0 0 0 X P1SKIP[0:7]
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SF Signals PIN I/O TX0 RX0 SCK (SPI1) MISO (SPI1) MOSI (SPI1) NSS* (SPI1) SCK (SPI0) MISO (SPI0) MOSI (SPI0) NSS* (SPI0) SDA SCL CP0 CP0A CP1 CP1A /SYSCLK CEX0 CEX1 CEX2 CEX3 CEX4 CEX5 ECI T0 T1
0
1
2
3
4
5
6
7
0
0
1
1
0
0
0
0
P0SKIP[0:7]
Figure 21.4. Crossbar Priority Decoder with Crystal Pins Skipped
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SFR Definition 21.1. XBR0: Port I/O Crossbar Register 0
Bit Name Type Reset 7 CP1AE R/W 0 6 CP1E R/W 0 5 CP0AE R/W 0 4 CP0E R/W 0 3 SYSCKE R/W 0 2 SMB0E R/W 0 1 SPI0E R/W 0 0 URT0E R/W 0
SFR Page = 0x0; SFR Address = 0xE1 Bit Name 7 CP1AE
Function
Comparator1 Asynchronous Output Enable. 0: Asynchronous CP1 output unavailable at Port pin. 1: Asynchronous CP1 output routed to Port pin.
6
CP1E
Comparator1 Output Enable. 0: CP1 output unavailable at Port pin. 1: CP1 output routed to Port pin.
5
CP0AE
Comparator0 Asynchronous Output Enable. 0: Asynchronous CP0 output unavailable at Port pin. 1: Asynchronous CP0 output routed to Port pin.
4
CP0E
Comparator0 Output Enable. 0: CP1 output unavailable at Port pin. 1: CP1 output routed to Port pin.
3
SYSCKE SYSCLK Output Enable. 0: SYSCLK output unavailable at Port pin. 1: SYSCLK output routed to Port pin.
2
SMB0E
SMBus I/O Enable. 0: SMBus I/O unavailable at Port pin. 1: SDA and SCL routed to Port pins.
1
SPI0E
SPI0 I/O Enable. 0: SPI0 I/O unavailable at Port pin. 1: SCK, MISO, and MOSI (for SPI0) routed to Port pins. NSS (for SPI0) routed to Port pin only if SPI0 is configured to 4-wire mode.
0
URT0E
UART0 Output Enable. 0: UART I/O unavailable at Port pin. 1: TX0 and RX0 routed to Port pins P0.4 and P0.5.
Note: SPI0 can be assigned either 3 or 4 Port I/O pins.
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SFR Definition 21.2. XBR1: Port I/O Crossbar Register 1
Bit Name Type Reset R/W 0 7 6 SPI1E R/W 0 5 T1E R/W 0 4 T0E R/W 0 3 ECIE R/W 0 R/W 0 2 1 PCA0ME[2:0] R/W 0 R/W 0 0
SFR Page = 0x0; SFR Address = 0xE2
Bit Name Function
7 6
Unused SPI1E
Unused. Read = 0b; Write = Don't Care. SPI1 I/O Enable. 0: SPI0 I/O unavailable at Port pin. 1: SCK (for SPI1) routed to P1.0. MISO (for SPI1) routed to P1.1. MOSI (for SPI1) routed to P1.2. NSS (for SPI1) routed to P1.3 only if SPI1 is configured to 4-wire mode.
5
T1E
Timer1 Input Enable. 0: T1 input unavailable at Port pin. 1: T1 input routed to Port pin.
4
T0E
Timer0 Input Enable. 0: T0 input unavailable at Port pin. 1: T0 input routed to Port pin.
3
ECIE
PCA0 External Counter Input (ECI) Enable. 0: PCA0 external counter input unavailable at Port pin. 1: PCA0 external counter input routed to Port pin.
2:0
PCA0ME PCA0 Module I/O Enable. 000: All PCA0 I/O unavailable at Port pin. 001: CEX0 routed to Port pin. 010: CEX0, CEX1 routed to Port pins. 011: CEX0, CEX1, CEX2 routed to Port pins. 100: CEX0, CEX1, CEX2 CEX3 routed to Port pins. 101: CEX0, CEX1, CEX2, CEX3, CEX4 routed to Port pins. 110: CEX0, CEX1, CEX2, CEX3, CEX4, CEX5 routed to Port pins. 111: Reserved.
Note: SPI1 can be assigned either 3 or 4 Port I/O pins.
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SFR Definition 21.3. XBR2: Port I/O Crossbar Register 2
Bit Name Type Reset 7 WEAKPUD R/W 0 6 XBARE R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 5 4 3 2 1 0
SFR Page = 0x0; SFR Address = 0xE3
Bit Name Function
7 WEAKPUD 6 XBARE
Port I/O Weak Pullup Disable. 0: Weak Pullups enabled (except for Port I/O pins configured for analog mode). Crossbar Enable. 0: Crossbar disabled. 1: Crossbar enabled.
5:0
Unused
Unused. Read = 000000b; Write = Don't Care.
Note: The Crossbar must be enabled (XBARE = 1) to use any Port pin as a digital output.
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21.4. Port Match
Port match functionality allows system events to be triggered by a logic value change on P0 or P1. A software controlled value stored in the PnMAT registers specifies the expected or normal logic values of P0 and P1. A Port mismatch event occurs if the logic levels of the Port's input pins no longer match the software controlled value. This allows Software to be notified if a certain change or pattern occurs on P0 or P1 input pins regardless of the XBRn settings. The PnMASK registers can be used to individually select which P0 and P1 pins should be compared against the PnMAT registers. A Port mismatch event is generated if (P0 & P0MASK) does not equal (PnMAT & P0MASK) or if (P1 & P1MASK) does not equal (PnMAT & P1MASK). A Port mismatch event may be used to generate an interrupt or wake the device from a low power mode. See Section "12. Interrupt Handler" on page 120 and Section "14. Power Management" on page 143 for more details on interrupt and wake-up sources.
SFR Definition 21.4. P0MASK: Port0 Mask Register
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
P0MASK[7:0] R/W 0 0 0 0
SFR Page= 0x0; SFR Address = 0xC7
Bit Name Function
7:0
P0MASK[7:0] Port0 Mask Value. Selects the P0 pins to be compared with the corresponding bits in P0MAT. 0: P0.n pin pad logic value is ignored and cannot cause a Port Mismatch event. 1: P0.n pin pad logic value is compared to P0MAT.n.
SFR Definition 21.5. P0MAT: Port0 Match Register
Bit Name Type Reset 1 1 1 1 7 6 5 4 3 2 1 0
P0MAT[7:0] R/W 1 1 1 1
SFR Page= 0x0; SFR Address = 0xD7 7:0 P0MAT[7:0] Port 0 Match Value. Match comparison value used on Port 0 for bits in P0MASK which are set to 1. 0: P0.n pin logic value is compared with logic LOW. 1: P0.n pin logic value is compared with logic HIGH.
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SFR Definition 21.6. P1MASK: Port1 Mask Register
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
P1MASK[7:0] R/W 0 0 0 0
SFR Page= 0x0; SFR Address = 0xBF Bit Name 7:0 P1MASK[7:0] Port 1 Mask Value.
Function
Selects P1 pins to be compared to the corresponding bits in P1MAT. 0: P1.n pin logic value is ignored and cannot cause a Port Mismatch event. 1: P1.n pin logic value is compared to P1MAT.n.
SFR Definition 21.7. P1MAT: Port1 Match Register
Bit Name Type Reset 1 1 1 1 7 6 5 4 3 2 1 0
P1MAT[7:0] R/W 1 1 1 1
SFR Page = 0x0; SFR Address = 0xCF Bit Name 7:0 P1MAT[7:0] Port 1 Match Value.
Function
Match comparison value used on Port 1 for bits in P1MASK which are set to 1. 0: P1.n pin logic value is compared with logic LOW. 1: P1.n pin logic value is compared with logic HIGH.
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21.5. Special Function Registers for Accessing and Configuring Port I/O
All Port I/O are accessed through corresponding special function registers (SFRs) that are both byte addressable and bit addressable. When writing to a Port, the value written to the SFR is latched to maintain the output data value at each pin. When reading, the logic levels of the Port's input pins are returned regardless of the XBRn settings (i.e., even when the pin is assigned to another signal by the Crossbar, the Port register can always read its corresponding Port I/O pin). The exception to this is the execution of the read-modify-write instructions that target a Port Latch register as the destination. The read-modify-write instructions when operating on a Port SFR are the following: ANL, ORL, XRL, JBC, CPL, INC, DEC, DJNZ and MOV, CLR or SETB, when the destination is an individual bit in a Port SFR. For these instructions, the value of the latch register (not the pin) is read, modified, and written back to the SFR. Each Port has a corresponding PnSKIP register which allows its individual Port pins to be assigned to digital functions or skipped by the Crossbar. All Port pins used for analog functions, GPIO, or dedicated digital functions such as the EMIF should have their PnSKIP bit set to 1. The Port input mode of the I/O pins is defined using the Port Input Mode registers (PnMDIN). Each Port cell can be configured for analog or digital I/O. This selection is required even for the digital resources selected in the XBRn registers, and is not automatic. The only exception to this is P2.7, which can only be used for digital I/O. The output driver characteristics of the I/O pins are defined using the Port Output Mode registers (PnMDOUT). Each Port Output driver can be configured as either open drain or push-pull. This selection is required even for the digital resources selected in the XBRn registers, and is not automatic. The only exception to this is the SMBus (SDA, SCL) pins, which are configured as open-drain regardless of the PnMDOUT settings. The drive strength of the output drivers are controlled by the Port Drive Strength (PnDRV) registers. The default is low drive strength. See Section "4. Electrical Characteristics" on page 36 for the difference in output drive strength between the two modes.
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SFR Definition 21.8. P0: Port0
Bit Name Type Reset 1 1 1 1 7 6 5 4 P0[7:0] R/W 1 1 1 1 3 2 1 0
SFR Page = All Pages; SFR Address = 0x80; Bit-Addressable Bit Name Description Write 7:0 P0[7:0] 0: Set output latch to logic LOW. Sets the Port latch logic value or reads the Port pin 1: Set output latch to logic logic state in Port cells con- HIGH. figured for digital I/O. Port 0 Data.
Read 0: P0.n Port pin is logic LOW. 1: P0.n Port pin is logic HIGH.
SFR Definition 21.9. P0SKIP: Port0 Skip
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
P0SKIP[7:0] R/W 0 0 0 0
SFR Page= 0x0; SFR Address = 0xD4 Bit Name 7:0 P0SKIP[7:0] Port 0 Crossbar Skip Enable Bits.
Function
These bits select Port 0 pins to be skipped by the Crossbar Decoder. Port pins used for analog, special functions or GPIO should be skipped by the Crossbar. 0: Corresponding P0.n pin is not skipped by the Crossbar. 1: Corresponding P0.n pin is skipped by the Crossbar.
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SFR Definition 21.10. P0MDIN: Port0 Input Mode
Bit Name Type Reset 1 1 1 1 7 6 5 4 3 2 1 0
P0MDIN[7:0] R/W 1 1 1 1
SFR Page= 0x0; SFR Address = 0xF1 Bit Name 7:0 P0MDIN[7:0]
Function
Analog Configuration Bits for P0.7-P0.0 (respectively). Port pins configured for analog mode have their weak pullup, and digital receiver disabled. The digital driver is not explicitly disabled. 0: Corresponding P0.n pin is configured for analog mode. 1: Corresponding P0.n pin is not configured for analog mode.
SFR Definition 21.11. P0MDOUT: Port0 Output Mode
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
P0MDOUT[7:0] R/W 0 0 0 0
SFR Page = 0x0; SFR Address = 0xA4 Bit Name 7:0
Function
P0MDOUT[7:0] Output Configuration Bits for P0.7-P0.0 (respectively). These bits control the digital driver even when the corresponding bit in register P0MDIN is logic 0. 0: Corresponding P0.n Output is open-drain. 1: Corresponding P0.n Output is push-pull.
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SFR Definition 21.12. P0DRV: Port0 Drive Strength
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
P0DRV[7:0] R/W 0 0 0 0
SFR Page = 0xF; SFR Address = 0xA4 Bit Name 7:0
Function
P0DRV[7:0] Drive Strength Configuration Bits for P0.7-P0.0 (respectively). Configures digital I/O Port cells to high or low output drive strength. 0: Corresponding P0.n Output has low output drive strength. 1: Corresponding P0.n Output has high output drive strength.
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SFR Definition 21.13. P1: Port1
Bit Name Type Reset 0 1 1 1 7 6 5 4 3 P1[6:0] R/W 1 1 1 1 2 1 0
SFR Page = All Pages; SFR Address = 0x90; Bit-Addressable Bit Name Description Write 7 6:0 Unused P1[6:0] Unused. Read =0b; Write = Don't Care. 0: Set output latch to logic LOW. Sets the Port latch logic value or reads the Port pin 1: Set output latch to logic logic state in Port cells con- HIGH. figured for digital I/O. Port 1 Data.
Read
0: P1.n Port pin is logic LOW. 1: P1.n Port pin is logic HIGH.
SFR Definition 21.14. P1SKIP: Port1 Skip
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 P1SKIP[6:0] R/W 0 0 0 0 2 1 0
SFR Page = 0x0; SFR Address = 0xD5 Bit Name 7 6:0 Unused Unused. Read =0b; Write = Don't Care. P1SKIP[6:0] Port 1 Crossbar Skip Enable Bits.
Function
These bits select Port 1 pins to be skipped by the Crossbar Decoder. Port pins used for analog, special functions or GPIO should be skipped by the Crossbar. 0: Corresponding P1.n pin is not skipped by the Crossbar. 1: Corresponding P1.n pin is skipped by the Crossbar.
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SFR Definition 21.15. P1MDIN: Port1 Input Mode
Bit Name Type Reset 1 1 1 1 7 6 5 4 3 P1MDIN[6:0] R/W 1 1 1 1 2 1 0
SFR Page = 0x0; SFR Address = 0xF2 Bit Name 7 6:0 Unused P1MDIN[6:0] Unused. Read =0b; Write = Don't Care.
Function
Analog Configuration Bits for P1.6-P1.0 (respectively). Port pins configured for analog mode have their weak pullup and digital receiver disabled. The digital driver is not explicitly disabled. 0: Corresponding P1.n pin is configured for analog mode. 1: Corresponding P1.n pin is not configured for analog mode.
SFR Definition 21.16. P1MDOUT: Port1 Output Mode
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 P1MDOUT[6:0] R/W 0 0 0 0 2 1 0
SFR Page = 0x0; SFR Address = 0xA5 Bit Name 7 6:0 Unused Unused. Read =0b; Write = Don't Care.
Function
P1MDOUT[6:0] Output Configuration Bits for P1.6-P1.0 (respectively). These bits control the digital driver even when the corresponding bit in register P1MDIN is logic 0. 0: Corresponding P1.n Output is open-drain. 1: Corresponding P1.n Output is push-pull.
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SFR Definition 21.17. P1DRV: Port1 Drive Strength
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 P1DRV[6:0] R/W 0 0 0 0 2 1 0
SFR Page = 0xF; SFR Address = 0xA5 Bit Name 7 6:0 Unused Unused. Read =0b; Write = Don't Care.
Function
P1DRV[6:0] Drive Strength Configuration Bits for P1.6-P1.0 (respectively). Configures digital I/O Port cells to high or low output drive strength. 0: Corresponding P1.n Output has low output drive strength. 1: Corresponding P1.n Output has high output drive strength.
SFR Definition 21.18. P2: Port2
Bit Name Type Reset 7 P2 R/W 1 0 0 0 0 0 0 0 6 5 4 3 2 1 0
SFR Page = All Pages; SFR Address = 0xA0; Bit-Addressable
Bit Name Description Read Write
7
P2
0: Set output latch to logic Port 2 Data. LOW. Sets the Port latch logic value or reads the Port pin 1: Set output latch to logic logic state in Port cells con- HIGH. figured for digital I/O. Unused. Read = 0000000b; Write = Don't Care.
0: P2.7 Port pin is logic LOW. 1: P2.7 Port pin is logic HIGH.
6:0
Unused
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SFR Definition 21.19. P2MDOUT: Port2 Output Mode
Bit 7 6 5 4 3 2 1 0
Name P2MDOUT Type Reset R/W 0 0 0 0 0 0 0 0
SFR Page = 0x0; SFR Address = 0xA6 Bit Name 7 P2MDOUT These bits control the digital driver. 0: P2.7 Output is open-drain. 1: P2.7 Output is push-pull. 6:0 Unused Unused.
Function
Output Configuration Bits for P2.7.
Read = 0000000b; Write = Don't Care.
SFR Definition 21.20. P2DRV: Port2 Drive Strength
Bit Name Type Reset 7 P2DRV R/W 0 0 0 0 0 0 0 0 6 5 4 3 2 1 0
SFR Page = 0x0F; SFR Address = 0xA6 Bit Name 7 P2DRV
Function
Drive Strength Configuration Bits for P2.7.
Configures digital I/O Port cells to high or low output drive strength. 0: P2.7 Output has low output drive strength. 1: P2.7 Output has high output drive strength. 6:0 Unused Unused. Read = 0000000b; Write = Don't Care.
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22. SMBus
The SMBus I/O interface is a two-wire, bi-directional serial bus. The SMBus is compliant with the System Management Bus Specification, version 1.1, and compatible with the I2C serial bus. Reads and writes to the interface by the system controller are byte oriented with the SMBus interface autonomously controlling the serial transfer of the data. Data can be transferred at up to 1/20th of the system clock as a master or slave (this can be faster than allowed by the SMBus specification, depending on the system clock used). A method of extending the clock-low duration is available to accommodate devices with different speed capabilities on the same bus. The SMBus interface may operate as a master and/or slave, and may function on a bus with multiple masters. The SMBus provides control of SDA (serial data), SCL (serial clock) generation and synchronization, arbitration logic, and START/STOP control and generation. The SMBus peripheral can be fully driven by software (i.e. software accepts/rejects slave addresses, and generates ACKs), or hardware slave address recognition and automatic ACK generation can be enabled to minimize software overhead. A block diagram of the SMBus peripheral and the associated SFRs is shown in Figure 22.1.
SMB0CN MTSSAAAS AXTTCRC I SMAOKBK TO RL ED QO RE S T SMB0CF E I BESSSS N N U XMMMM SHSTBBBB M YHTFCC B OOT S S LEE10 D
00 01 10 11 SMBUS CONTROL LOGIC Arbitration SCL Synchronization SCL Generation (Master Mode) SDA Control Hardware Slave Address Recognition Hardware ACK Generation Data Path IRQ Generation Control
T0 Overflow T1 Overflow TMR2H Overflow TMR2L Overflow SCL
FILTER
Interrupt Request
SCL Control
N
SDA Control
C R O S S B A R SDA
Port I/O
SMB0DAT 76543210 S L V 6 S L V 5 S L V 4 S L V 3 S L V 2 S L V 1 SG LC V 0 SSSSSSS LLLLLLL VVVVVVV MMMMMMM 6543210 SMB0ADM E H A C K
FILTER
SMB0ADR
N
Figure 22.1. SMBus Block Diagram
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22.1. Supporting Documents
It is assumed the reader is familiar with or has access to the following supporting documents: 1. The I2C-Bus and How to Use It (including specifications), Philips Semiconductor. 2. The I2C-Bus Specification--Version 2.0, Philips Semiconductor. 3. System Management Bus Specification--Version 1.1, SBS Implementers Forum.
22.2. SMBus Configuration
Figure 22.2 shows a typical SMBus configuration. The SMBus specification allows any recessive voltage between 3.0 V and 5.0 V; different devices on the bus may operate at different voltage levels. The bi-directional SCL (serial clock) and SDA (serial data) lines must be connected to a positive power supply voltage through a pullup resistor or similar circuit. Every device connected to the bus must have an open-drain or open-collector output for both the SCL and SDA lines, so that both are pulled high (recessive state) when the bus is free. The maximum number of devices on the bus is limited only by the requirement that the rise and fall times on the bus not exceed 300 ns and 1000 ns, respectively.
VDD = 5 V
VDD = 3 V
VDD = 5 V
VDD = 3 V
Master Device
Slave Device 1
Slave Device 2
SDA SCL
Figure 22.2. Typical SMBus Configuration
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22.3. SMBus Operation
Two types of data transfers are possible: data transfers from a master transmitter to an addressed slave receiver (WRITE), and data transfers from an addressed slave transmitter to a master receiver (READ). The master device initiates both types of data transfers and provides the serial clock pulses on SCL. The SMBus interface may operate as a master or a slave, and multiple master devices on the same bus are supported. If two or more masters attempt to initiate a data transfer simultaneously, an arbitration scheme is employed with a single master always winning the arbitration. Note that it is not necessary to specify one device as the Master in a system; any device who transmits a START and a slave address becomes the master for the duration of that transfer. A typical SMBus transaction consists of a START condition followed by an address byte (Bits7-1: 7-bit slave address; Bit0: R/W direction bit), one or more bytes of data, and a STOP condition. Bytes that are received (by a master or slave) are acknowledged (ACK) with a low SDA during a high SCL (see Figure 22.3). If the receiving device does not ACK, the transmitting device will read a NACK (not acknowledge), which is a high SDA during a high SCL. The direction bit (R/W) occupies the least-significant bit position of the address byte. The direction bit is set to logic 1 to indicate a "READ" operation and cleared to logic 0 to indicate a "WRITE" operation. All transactions are initiated by a master, with one or more addressed slave devices as the target. The master generates the START condition and then transmits the slave address and direction bit. If the transaction is a WRITE operation from the master to the slave, the master transmits the data a byte at a time waiting for an ACK from the slave at the end of each byte. For READ operations, the slave transmits the data waiting for an ACK from the master at the end of each byte. At the end of the data transfer, the master generates a STOP condition to terminate the transaction and free the bus. Figure 22.3 illustrates a typical SMBus transaction.
SCL
SDA SLA6 SLA5-0 R/W D7 D6-0
START
Slave Address + R/W
ACK
Data Byte
NACK
STOP
Figure 22.3. SMBus Transaction 22.3.1. Transmitter Vs. Receiver
On the SMBus communications interface, a device is the "transmitter" when it is sending an address or data byte to another device on the bus. A device is a "receiver" when an address or data byte is being sent to it from another device on the bus. The transmitter controls the SDA line during the address or data byte. After each byte of address or data information is sent by the transmitter, the receiver sends an ACK or NACK bit during the ACK phase of the transfer, during which time the receiver controls the SDA line.
22.3.2. Arbitration
A master may start a transfer only if the bus is free. The bus is free after a STOP condition or after the SCL and SDA lines remain high for a specified time (see Section "22.3.5. SCL High (SMBus Free) Timeout" on page 228). In the event that two or more devices attempt to begin a transfer at the same time, an arbitration scheme is employed to force one master to give up the bus. The master devices continue transmitting until one attempts a HIGH while the other transmits a LOW. Since the bus is open-drain, the bus will be pulled LOW. The master attempting the HIGH will detect a LOW SDA and lose the arbitration. The winning
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master continues its transmission without interruption; the losing master becomes a slave and receives the rest of the transfer if addressed. This arbitration scheme is non-destructive: one device always wins, and no data is lost.
22.3.3. Clock Low Extension
SMBus provides a clock synchronization mechanism, similar to I2C, which allows devices with different speed capabilities to coexist on the bus. A clock-low extension is used during a transfer in order to allow slower slave devices to communicate with faster masters. The slave may temporarily hold the SCL line LOW to extend the clock low period, effectively decreasing the serial clock frequency.
22.3.4. SCL Low Timeout
If the SCL line is held low by a slave device on the bus, no further communication is possible. Furthermore, the master cannot force the SCL line high to correct the error condition. To solve this problem, the SMBus protocol specifies that devices participating in a transfer must detect any clock cycle held low longer than 25 ms as a "timeout" condition. Devices that have detected the timeout condition must reset the communication no later than 10 ms after detecting the timeout condition. When the SMBTOE bit in SMB0CF is set, Timer 3 is used to detect SCL low timeouts. Timer 3 is forced to reload when SCL is high, and allowed to count when SCL is low. With Timer 3 enabled and configured to overflow after 25 ms (and SMBTOE set), the Timer 3 interrupt service routine can be used to reset (disable and re-enable) the SMBus in the event of an SCL low timeout.
22.3.5. SCL High (SMBus Free) Timeout
The SMBus specification stipulates that if the SCL and SDA lines remain high for more that 50 s, the bus is designated as free. When the SMBFTE bit in SMB0CF is set, the bus will be considered free if SCL and SDA remain high for more than 10 SMBus clock source periods (as defined by the timer configured for the SMBus clock source). If the SMBus is waiting to generate a Master START, the START will be generated following this timeout. Note that a clock source is required for free timeout detection, even in a slave-only implementation.
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22.4. Using the SMBus
The SMBus can operate in both Master and Slave modes. The interface provides timing and shifting control for serial transfers; higher level protocol is determined by user software. The SMBus interface provides the following application-independent features:
* * * * * * * *
Byte-wise serial data transfers Clock signal generation on SCL (Master Mode only) and SDA data synchronization Timeout/bus error recognition, as defined by the SMB0CF configuration register START/STOP timing, detection, and generation Bus arbitration Interrupt generation Status information Optional hardware recognition of slave address and automatic acknowledgement of address/data
SMBus interrupts are generated for each data byte or slave address that is transferred. When hardware acknowledgement is disabled, the point at which the interrupt is generated depends on whether the hardware is acting as a data transmitter or receiver. When a transmitter (i.e. sending address/data, receiving an ACK), this interrupt is generated after the ACK cycle so that software may read the received ACK value; when receiving data (i.e. receiving address/data, sending an ACK), this interrupt is generated before the ACK cycle so that software may define the outgoing ACK value. If hardware acknowledgement is enabled, these interrupts are always generated after the ACK cycle. See Section 22.5 for more details on transmission sequences. Interrupts are also generated to indicate the beginning of a transfer when a master (START generated), or the end of a transfer when a slave (STOP detected). Software should read the SMB0CN (SMBus Control register) to find the cause of the SMBus interrupt. The SMB0CN register is described in Section 22.4.2; Table 22.5 provides a quick SMB0CN decoding reference.
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22.4.1. SMBus Configuration Register
The SMBus Configuration register (SMB0CF) is used to enable the SMBus Master and/or Slave modes, select the SMBus clock source, and select the SMBus timing and timeout options. When the ENSMB bit is set, the SMBus is enabled for all master and slave events. Slave events may be disabled by setting the INH bit. With slave events inhibited, the SMBus interface will still monitor the SCL and SDA pins; however, the interface will NACK all received addresses and will not generate any slave interrupts. When the INH bit is set, all slave events will be inhibited following the next START (interrupts will continue for the duration of the current transfer).
Table 22.1. SMBus Clock Source Selection
SMBCS1 0 0 1 1 SMBCS0 0 1 0 1 SMBus Clock Source Timer 0 Overflow Timer 1 Overflow Timer 2 High Byte Overflow Timer 2 Low Byte Overflow
The SMBCS1-0 bits select the SMBus clock source, which is used only when operating as a master or when the Free Timeout detection is enabled. When operating as a master, overflows from the selected source determine the absolute minimum SCL low and high times as defined in Equation 22.1. Note that the selected clock source may be shared by other peripherals so long as the timer is left running at all times. For example, Timer 1 overflows may generate the SMBus and UART baud rates simultaneously. Timer configuration is covered in Section "25. Timers" on page 270.
1 T HighMin = T LowMin = --------------------------------------------f ClockSourceOverflow
Equation 22.1. Minimum SCL High and Low Times
The selected clock source should be configured to establish the minimum SCL High and Low times as per Equation 22.1. When the interface is operating as a master (and SCL is not driven or extended by any other devices on the bus), the typical SMBus bit rate is approximated by Equation 22.2.
f ClockSourceOverflow BitRate = --------------------------------------------3
Equation 22.2. Typical SMBus Bit Rate
Figure 22.4 shows the typical SCL generation described by Equation 22.2. Notice that THIGH is typically twice as large as TLOW. The actual SCL output may vary due to other devices on the bus (SCL may be extended low by slower slave devices, or driven low by contending master devices). The bit rate when operating as a master will never exceed the limits defined by equation Equation 22.1.
Timer Source Overflows SCL
TLow
THigh
SCL High Timeout
Figure 22.4. Typical SMBus SCL Generation
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Setting the EXTHOLD bit extends the minimum setup and hold times for the SDA line. The minimum SDA setup time defines the absolute minimum time that SDA is stable before SCL transitions from low-to-high. The minimum SDA hold time defines the absolute minimum time that the current SDA value remains stable after SCL transitions from high-to-low. EXTHOLD should be set so that the minimum setup and hold times meet the SMBus Specification requirements of 250 ns and 300 ns, respectively. Table 22.2 shows the minimum setup and hold times for the two EXTHOLD settings. Setup and hold time extensions are typically necessary when SYSCLK is above 10 MHz.
Table 22.2. Minimum SDA Setup and Hold Times
EXTHOLD 0 1 Minimum SDA Setup Time Tlow - 4 system clocks or 1 system clock + s/w delay* 11 system clocks Minimum SDA Hold Time 3 system clocks 12 system clocks
*Note: Setup Time for ACK bit transmissions and the MSB of all data transfers. When using software acknowledgement, the s/w delay occurs between the time SMB0DAT or ACK is written and when SI is cleared. Note that if SI is cleared in the same write that defines the outgoing ACK value, s/w delay is zero.
With the SMBTOE bit set, Timer 3 should be configured to overflow after 25 ms in order to detect SCL low timeouts (see Section "22.3.4. SCL Low Timeout" on page 228). The SMBus interface will force Timer 3 to reload while SCL is high, and allow Timer 3 to count when SCL is low. The Timer 3 interrupt service routine should be used to reset SMBus communication by disabling and re-enabling the SMBus. SMBus Free Timeout detection can be enabled by setting the SMBFTE bit. When this bit is set, the bus will be considered free if SDA and SCL remain high for more than 10 SMBus clock source periods (see Figure 22.4).
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SFR Definition 22.1. SMB0CF: SMBus Clock/Configuration
Bit Name Type Reset 7 ENSMB R/W 0 6 INH R/W 0 5 BUSY R 0 4 3 2 SMBFTE R/W 0 0 1 0
EXTHOLD SMBTOE R/W 0 R/W 0
SMBCS[1:0] R/W 0
SFR Page = 0x0; SFR Address = 0xC1 Bit Name 7 ENSMB SMBus Enable.
Function
This bit enables the SMBus interface when set to 1. When enabled, the interface constantly monitors the SDA and SCL pins. 6 INH SMBus Slave Inhibit. When this bit is set to logic 1, the SMBus does not generate an interrupt when slave events occur. This effectively removes the SMBus slave from the bus. Master Mode interrupts are not affected. 5 BUSY SMBus Busy Indicator. This bit is set to logic 1 by hardware when a transfer is in progress. It is cleared to logic 0 when a STOP or free-timeout is sensed. 4 EXTHOLD SMBus Setup and Hold Time Extension Enable. This bit controls the SDA setup and hold times according to Table 22.2. 0: SDA Extended Setup and Hold Times disabled. 1: SDA Extended Setup and Hold Times enabled. 3 SMBTOE SMBus SCL Timeout Detection Enable. This bit enables SCL low timeout detection. If set to logic 1, the SMBus forces Timer 3 to reload while SCL is high and allows Timer 3 to count when SCL goes low. If Timer 3 is configured to Split Mode, only the High Byte of the timer is held in reload while SCL is high. Timer 3 should be programmed to generate interrupts at 25 ms, and the Timer 3 interrupt service routine should reset SMBus communication. 2 SMBFTE SMBus Free Timeout Detection Enable. When this bit is set to logic 1, the bus will be considered free if SCL and SDA remain high for more than 10 SMBus clock source periods. 1:0 SMBCS[1:0] SMBus Clock Source Selection. These two bits select the SMBus clock source, which is used to generate the SMBus bit rate. The selected device should be configured according to Equation 22.1. 00: Timer 0 Overflow 01: Timer 1 Overflow 10:Timer 2 High Byte Overflow 11: Timer 2 Low Byte Overflow
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22.4.2. SMB0CN Control Register
SMB0CN is used to control the interface and to provide status information (see SFR Definition 22.2). The higher four bits of SMB0CN (MASTER, TXMODE, STA, and STO) form a status vector that can be used to jump to service routines. MASTER indicates whether a device is the master or slave during the current transfer. TXMODE indicates whether the device is transmitting or receiving data for the current byte. STA and STO indicate that a START and/or STOP has been detected or generated since the last SMBus interrupt. STA and STO are also used to generate START and STOP conditions when operating as a master. Writing a 1 to STA will cause the SMBus interface to enter Master Mode and generate a START when the bus becomes free (STA is not cleared by hardware after the START is generated). Writing a 1 to STO while in Master Mode will cause the interface to generate a STOP and end the current transfer after the next ACK cycle. If STO and STA are both set (while in Master Mode), a STOP followed by a START will be generated. The ARBLOST bit indicates that the interface has lost an arbitration. This may occur anytime the interface is transmitting (master or slave). A lost arbitration while operating as a slave indicates a bus error condition. ARBLOST is cleared by hardware each time SI is cleared. The SI bit (SMBus Interrupt Flag) is set at the beginning and end of each transfer, after each byte frame, or when an arbitration is lost; see Table 22.3 for more details. Important Note About the SI Bit: The SMBus interface is stalled while SI is set; thus SCL is held low, and the bus is stalled until software clears SI. 22.4.2.1.Software ACK Generation When the EHACK bit in register SMB0ADM is cleared to 0, the firmware on the device must detect incoming slave addresses and ACK or NACK the slave address and incoming data bytes. As a receiver, writing the ACK bit defines the outgoing ACK value; as a transmitter, reading the ACK bit indicates the value received during the last ACK cycle. ACKRQ is set each time a byte is received, indicating that an outgoing ACK value is needed. When ACKRQ is set, software should write the desired outgoing value to the ACK bit before clearing SI. A NACK will be generated if software does not write the ACK bit before clearing SI. SDA will reflect the defined ACK value immediately following a write to the ACK bit; however SCL will remain low until SI is cleared. If a received slave address is not acknowledged, further slave events will be ignored until the next START is detected. 22.4.2.2.Hardware ACK Generation When the EHACK bit in register SMB0ADM is set to 1, automatic slave address recognition and ACK generation is enabled. More detail about automatic slave address recognition can be found in Section 22.4.3. As a receiver, the value currently specified by the ACK bit will be automatically sent on the bus during the ACK cycle of an incoming data byte. As a transmitter, reading the ACK bit indicates the value received on the last ACK cycle. The ACKRQ bit is not used when hardware ACK generation is enabled. If a received slave address is NACKed by hardware, further slave events will be ignored until the next START is detected, and no interrupt will be generated. Table 22.3 lists all sources for hardware changes to the SMB0CN bits. Refer to Table 22.5 for SMBus status decoding using the SMB0CN register.
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SFR Definition 22.2. SMB0CN: SMBus Control
Bit Name Type Reset 7 MASTER R 0 6 TXMODE R 0 5 STA R/W 0 4 STO R/W 0 3 ACKRQ R 0 2 ARBLOST R 0 1 ACK R/W 0 0 SI R/W 0
SFR Page = 0x0; SFR Address = 0xC0; Bit-Addressable Bit Name Description 7 MASTER SMBus Master/Slave Indicator. This read-only bit indicates when the SMBus is operating as a master. TXMODE SMBus Transmit Mode Indicator. This read-only bit indicates when the SMBus is operating as a transmitter. STA SMBus Start Flag.
Read N/A
Write
0: SMBus operating in slave mode. 1: SMBus operating in master mode. 0: SMBus in Receiver Mode. 1: SMBus in Transmitter Mode. 0: No Start or repeated Start detected. 1: Start or repeated Start detected. 0: No Stop condition detected. 1: Stop condition detected (if in Slave Mode) or pending (if in Master Mode).
6
N/A
5
0: No Start generated. 1: When Configured as a Master, initiates a START or repeated START. 0: No STOP condition is transmitted. 1: When configured as a Master, causes a STOP condition to be transmitted after the next ACK cycle. Cleared by Hardware. N/A N/A 0: Send NACK 1: Send ACK 0: Clear interrupt, and initiate next state machine event. 1: Force interrupt.
4
STO
SMBus Stop Flag.
3 2 1 0
ACKRQ
SMBus Acknowledge Request.
0: No Ack requested 1: ACK requested 0: No arbitration error. 1: Arbitration Lost 0: NACK received. 1: ACK received. 0: No interrupt pending
ARBLOST SMBus Arbitration Lost Indicator. ACK SI SMBus Acknowledge. SMBus Interrupt Flag.
This bit is set by hardware 1: Interrupt Pending under the conditions listed in Table 15.3. SI must be cleared by software. While SI is set, SCL is held low and the SMBus is stalled.
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Table 22.3. Sources for Hardware Changes to SMB0CN
Bit MASTER Set by Hardware When: * A START is generated. * START is generated. * SMB0DAT is written before the start of an SMBus frame. * A START followed by an address byte is received. * A STOP is detected while addressed as a slave. * Arbitration is lost due to a detected STOP. * A byte has been received and an ACK response value is needed (only when hardware ACK is not enabled). * A repeated START is detected as a MASTER when STA is low (unwanted repeated START). * SCL is sensed low while attempting to generate a STOP or repeated START condition. * SDA is sensed low while transmitting a 1 (excluding ACK bits). * The incoming ACK value is low (ACKNOWLEDGE). * A START has been generated. * Lost arbitration. * A byte has been transmitted and an ACK/NACK received. * A byte has been received. * A START or repeated START followed by a slave address + R/W has been received. * A STOP has been received. Cleared by Hardware When: * A STOP is generated. * Arbitration is lost. * A START is detected. * Arbitration is lost. * SMB0DAT is not written before the start of an SMBus frame. * Must be cleared by software. * A pending STOP is generated.
TXMODE
STA STO
ACKRQ
* After each ACK cycle.
ARBLOST
* Each time SI is cleared.
ACK
* The incoming ACK value is high (NOT ACKNOWLEDGE).
SI
* Must be cleared by software.
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22.4.3. Hardware Slave Address Recognition
The SMBus hardware has the capability to automatically recognize incoming slave addresses and send an ACK without software intervention. Automatic slave address recognition is enabled by setting the EHACK bit in register SMB0ADM to 1. This will enable both automatic slave address recognition and automatic hardware ACK generation for received bytes (as a master or slave). More detail on automatic hardware ACK generation can be found in Section 22.4.2.2. The registers used to define which address(es) are recognized by the hardware are the SMBus Slave Address register (SFR Definition 22.3) and the SMBus Slave Address Mask register (SFR Definition 22.4). A single address or range of addresses (including the General Call Address 0x00) can be specified using these two registers. The most-significant seven bits of the two registers are used to define which addresses will be ACKed. A 1 in bit positions of the slave address mask SLVM[6:0] enable a comparison between the received slave address and the hardware's slave address SLV[6:0] for those bits. A 0 in a bit of the slave address mask means that bit will be treated as a "don't care" for comparison purposes. In this case, either a 1 or a 0 value are acceptable on the incoming slave address. Additionally, if the GC bit in register SMB0ADR is set to 1, hardware will recognize the General Call Address (0x00). Table 22.4 shows some example parameter settings and the slave addresses that will be recognized by hardware under those conditions.
Table 22.4. Hardware Address Recognition Examples (EHACK = 1)
Hardware Slave Address SLV[6:0] 0x34 0x34 0x34 0x34 0x70 Slave Address Mask SLVM[6:0] 0x7F 0x7F 0x7E 0x7E 0x73 GC bit 0 1 0 1 0 Slave Addresses Recognized by Hardware 0x34 0x34, 0x00 (General Call) 0x34, 0x35 0x34, 0x35, 0x00 (General Call) 0x70, 0x74, 0x78, 0x7C
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SFR Definition 22.3. SMB0ADR: SMBus Slave Address
Bit Name Type Reset 0 0 0 7 6 5 4 SLV[6:0] R/W 0 0 0 0 3 2 1 0 GC R/W 0
SFR Page = 0x0; SFR Address = 0xF4 Bit Name 7:1 SLV[6:0] SMBus Hardware Slave Address.
Function
Defines the SMBus Slave Address(es) for automatic hardware acknowledgement. Only address bits which have a 1 in the corresponding bit position in SLVM[6:0] are checked against the incoming address. This allows multiple addresses to be recognized. 0 GC General Call Address Enable. When hardware address recognition is enabled (EHACK = 1), this bit will determine whether the General Call Address (0x00) is also recognized by hardware. 0: General Call Address is ignored. 1: General Call Address is recognized.
SFR Definition 22.4. SMB0ADM: SMBus Slave Address Mask
Bit Name Type Reset 1 1 1 7 6 5 4 SLVM[6:0] R/W 1 1 1 1 3 2 1 0 EHACK R/W 0
SFR Page = 0x0; SFR Address = 0xF5 Bit Name 7:1 SLVM[6:0] SMBus Slave Address Mask.
Function
Defines which bits of register SMB0ADR are compared with an incoming address byte, and which bits are ignored. Any bit set to 1 in SLVM[6:0] enables comparisons with the corresponding bit in SLV[6:0]. Bits set to 0 are ignored (can be either 0 or 1 in the incoming address). 0 EHACK Hardware Acknowledge Enable. Enables hardware acknowledgement of slave address and received data bytes. 0: Firmware must manually acknowledge all incoming address and data bytes. 1: Automatic Slave Address Recognition and Hardware Acknowledge is Enabled.
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22.4.4. Data Register
The SMBus Data register SMB0DAT holds a byte of serial data to be transmitted or one that has just been received. Software may safely read or write to the data register when the SI flag is set. Software should not attempt to access the SMB0DAT register when the SMBus is enabled and the SI flag is cleared to logic 0, as the interface may be in the process of shifting a byte of data into or out of the register. Data in SMB0DAT is always shifted out MSB first. After a byte has been received, the first bit of received data is located at the MSB of SMB0DAT. While data is being shifted out, data on the bus is simultaneously being shifted in. SMB0DAT always contains the last data byte present on the bus. In the event of lost arbitration, the transition from master transmitter to slave receiver is made with the correct data or address in SMB0DAT.
SFR Definition 22.5. SMB0DAT: SMBus Data
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
SMB0DAT[7:0] R/W 0 0 0 0
SFR Page = 0x0; SFR Address = 0xC2 Bit Name 7:0 SMB0DAT[7:0] SMBus Data.
Function
The SMB0DAT register contains a byte of data to be transmitted on the SMBus serial interface or a byte that has just been received on the SMBus serial interface. The CPU can read from or write to this register whenever the SI serial interrupt flag (SMB0CN.0) is set to logic 1. The serial data in the register remains stable as long as the SI flag is set. When the SI flag is not set, the system may be in the process of shifting data in/out and the CPU should not attempt to access this register.
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22.5. SMBus Transfer Modes
The SMBus interface may be configured to operate as master and/or slave. At any particular time, it will be operating in one of the following four modes: Master Transmitter, Master Receiver, Slave Transmitter, or Slave Receiver. The SMBus interface enters Master Mode any time a START is generated, and remains in Master Mode until it loses an arbitration or generates a STOP. An SMBus interrupt is generated at the end of all SMBus byte frames. Note that the position of the ACK interrupt when operating as a receiver depends on whether hardware ACK generation is enabled. As a receiver, the interrupt for an ACK occurs before the ACK with hardware ACK generation disabled, and after the ACK when hardware ACK generation is enabled. As a transmitter, interrupts occur after the ACK, regardless of whether hardware ACK generation is enabled or not.
22.5.1. Write Sequence (Master)
During a write sequence, an SMBus master writes data to a slave device. The master in this transfer will be a transmitter during the address byte, and a transmitter during all data bytes. The SMBus interface generates the START condition and transmits the first byte containing the address of the target slave and the data direction bit. In this case the data direction bit (R/W) will be logic 0 (WRITE). The master then transmits one or more bytes of serial data. After each byte is transmitted, an acknowledge bit is generated by the slave. The transfer is ended when the STO bit is set and a STOP is generated. Note that the interface will switch to Master Receiver Mode if SMB0DAT is not written following a Master Transmitter interrupt. Figure 22.5 shows a typical master write sequence. Two transmit data bytes are shown, though any number of bytes may be transmitted. Notice that all of the `data byte transferred' interrupts occur after the ACK cycle in this mode, regardless of whether hardware ACK generation is enabled.
Interrupts with Hardware ACK Enabled (EHACK = 1)
S
SLA
W
A
Data Byte
A
Data Byte
A
P
Interrupts with Hardware ACK Disabled (EHACK = 0) Received by SMBus Interface Transmitted by SMBus Interface S = START P = STOP A = ACK W = WRITE SLA = Slave Address
Figure 22.5. Typical Master Write Sequence
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22.5.2. Read Sequence (Master)
During a read sequence, an SMBus master reads data from a slave device. The master in this transfer will be a transmitter during the address byte, and a receiver during all data bytes. The SMBus interface generates the START condition and transmits the first byte containing the address of the target slave and the data direction bit. In this case the data direction bit (R/W) will be logic 1 (READ). Serial data is then received from the slave on SDA while the SMBus outputs the serial clock. The slave transmits one or more bytes of serial data. If hardware ACK generation is disabled, the ACKRQ is set to 1 and an interrupt is generated after each received byte. Software must write the ACK bit at that time to ACK or NACK the received byte. With hardware ACK generation enabled, the SMBus hardware will automatically generate the ACK/NACK, and then post the interrupt. It is important to note that the appropriate ACK or NACK value should be set up by the software prior to receiving the byte when hardware ACK generation is enabled. Writing a 1 to the ACK bit generates an ACK; writing a 0 generates a NACK. Software should write a 0 to the ACK bit for the last data transfer, to transmit a NACK. The interface exits Master Receiver Mode after the STO bit is set and a STOP is generated. The interface will switch to Master Transmitter Mode if SMB0DAT is written while an active Master Receiver. Figure 22.6 shows a typical master read sequence. Two received data bytes are shown, though any number of bytes may be received. Notice that the `data byte transferred' interrupts occur at different places in the sequence, depending on whether hardware ACK generation is enabled. The interrupt occurs before the ACK with hardware ACK generation disabled, and after the ACK when hardware ACK generation is enabled.
Interrupts with Hardware ACK Enabled (EHACK = 1)
S
SLA
R
A
Data Byte
A
Data Byte
N
P
Interrupts with Hardware ACK Disabled (EHACK = 0) Received by SMBus Interface Transmitted by SMBus Interface S = START P = STOP A = ACK N = NACK R = READ SLA = Slave Address
Figure 22.6. Typical Master Read Sequence
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22.5.3. Write Sequence (Slave)
During a write sequence, an SMBus master writes data to a slave device. The slave in this transfer will be a receiver during the address byte, and a receiver during all data bytes. When slave events are enabled (INH = 0), the interface enters Slave Receiver Mode when a START followed by a slave address and direction bit (WRITE in this case) is received. If hardware ACK generation is disabled, upon entering Slave Receiver Mode, an interrupt is generated and the ACKRQ bit is set. The software must respond to the received slave address with an ACK, or ignore the received slave address with a NACK. If hardware ACK generation is enabled, the hardware will apply the ACK for a slave address which matches the criteria set up by SMB0ADR and SMB0ADM. The interrupt will occur after the ACK cycle. If the received slave address is ignored (by software or hardware), slave interrupts will be inhibited until the next START is detected. If the received slave address is acknowledged, zero or more data bytes are received. If hardware ACK generation is disabled, the ACKRQ is set to 1 and an interrupt is generated after each received byte. Software must write the ACK bit at that time to ACK or NACK the received byte. With hardware ACK generation enabled, the SMBus hardware will automatically generate the ACK/NACK, and then post the interrupt. It is important to note that the appropriate ACK or NACK value should be set up by the software prior to receiving the byte when hardware ACK generation is enabled. The interface exits Slave Receiver Mode after receiving a STOP. Note that the interface will switch to Slave Transmitter Mode if SMB0DAT is written while an active Slave Receiver. Figure 22.7 shows a typical slave write sequence. Two received data bytes are shown, though any number of bytes may be received. Notice that the `data byte transferred' interrupts occur at different places in the sequence, depending on whether hardware ACK generation is enabled. The interrupt occurs before the ACK with hardware ACK generation disabled, and after the ACK when hardware ACK generation is enabled.
Interrupts with Hardware ACK Enabled (EHACK = 1)
S
SLA
W
A
Data Byte
A
Data Byte
A
P
Interrupts with Hardware ACK Disabled (EHACK = 0) Received by SMBus Interface Transmitted by SMBus Interface S = START P = STOP A = ACK W = WRITE SLA = Slave Address
Figure 22.7. Typical Slave Write Sequence
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22.5.4. Read Sequence (Slave)
During a read sequence, an SMBus master reads data from a slave device. The slave in this transfer will be a receiver during the address byte, and a transmitter during all data bytes. When slave events are enabled (INH = 0), the interface enters Slave Receiver Mode (to receive the slave address) when a START followed by a slave address and direction bit (READ in this case) is received. If hardware ACK generation is disabled, upon entering Slave Receiver Mode, an interrupt is generated and the ACKRQ bit is set. The software must respond to the received slave address with an ACK, or ignore the received slave address with a NACK. If hardware ACK generation is enabled, the hardware will apply the ACK for a slave address which matches the criteria set up by SMB0ADR and SMB0ADM. The interrupt will occur after the ACK cycle. If the received slave address is ignored (by software or hardware), slave interrupts will be inhibited until the next START is detected. If the received slave address is acknowledged, zero or more data bytes are transmitted. If the received slave address is acknowledged, data should be written to SMB0DAT to be transmitted. The interface enters Slave Transmitter Mode, and transmits one or more bytes of data. After each byte is transmitted, the master sends an acknowledge bit; if the acknowledge bit is an ACK, SMB0DAT should be written with the next data byte. If the acknowledge bit is a NACK, SMB0DAT should not be written to before SI is cleared (Note: an error condition may be generated if SMB0DAT is written following a received NACK while in Slave Transmitter Mode). The interface exits Slave Transmitter Mode after receiving a STOP. Note that the interface will switch to Slave Receiver Mode if SMB0DAT is not written following a Slave Transmitter interrupt. Figure 22.8 shows a typical slave read sequence. Two transmitted data bytes are shown, though any number of bytes may be transmitted. Notice that all of the `data byte transferred' interrupts occur after the ACK cycle in this mode, regardless of whether hardware ACK generation is enabled.
Interrupts with Hardware ACK Enabled (EHACK = 1)
S
SLA
R
A
Data Byte
A
Data Byte
N
P
Interrupts with Hardware ACK Disabled (EHACK = 0) Received by SMBus Interface Transmitted by SMBus Interface S = START P = STOP N = NACK R = READ SLA = Slave Address
Figure 22.8. Typical Slave Read Sequence
22.6. SMBus Status Decoding
The current SMBus status can be easily decoded using the SMB0CN register. The appropriate actions to take in response to an SMBus event depend on whether hardware slave address recognition and ACK generation is enabled or disabled. Table 22.5 describes the typical actions when hardware slave address recognition and ACK generation is disabled. Table 22.6 describes the typical actions when hardware slave address recognition and ACK generation is enabled. In the tables, STATUS VECTOR refers to the four upper bits of SMB0CN: MASTER, TXMODE, STA, and STO. The shown response options are only the typical responses; application-specific procedures are allowed as long as they conform to the SMBus specification. Highlighted responses are allowed by hardware but do not conform to the SMBus specification.
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Table 22.5. SMBus Status Decoding With Hardware ACK Generation Disabled (EHACK = 0)
Values to Write ACK 1 0 0 1 0 1 0 Current SMbus State Typical Response Options STO STA Next Status Vector Expected 1100 1110 1100 1110 1000 1000 1110 1110 1110 1100 1100
243
Values Read Mode ARBLOST ACKRQ Status Vector
ACK
1110
0 0
0X 0
A master START was generated.
Load slave address + R/W into SMB0DAT.
0 1 0 0 0
0X 0X 1X 0X 1X 1X 0X 0X 0 1 1 0 0 0
Master Transmitter
A master data or address byte Set STA to restart transfer. 0 was transmitted; NACK Abort transfer. received. Load next data byte into SMB0DAT.
1100 0 0
End transfer with STOP.
A master data or address byte End transfer with STOP and start 1 1 was transmitted; ACK another transfer. received. Send repeated START. 1 Switch to Master Receiver Mode (clear SI without writing new data 0 to SMB0DAT). Acknowledge received byte; Read SMB0DAT. 0
Send NACK to indicate last byte, 0 and send STOP. Send NACK to indicate last byte, and send STOP followed by 1 START. 1000 1 0X A master data byte was received; ACK requested. Send ACK followed by repeated START. 1
Master Receiver
Send NACK to indicate last byte, 1 and send repeated START. Send ACK and switch to Master Transmitter Mode (write to SMB0DAT before clearing SI). Send NACK and switch to Master Transmitter Mode (write to SMB0DAT before clearing SI). 0
0
0
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Table 22.5. SMBus Status Decoding With Hardware ACK Generation Disabled (EHACK = 0) (Continued)
Values Read Mode ARBLOST ACKRQ Status Vector Current SMbus State Typical Response Options STO STA Values to Write ACK 1 1 0 1 1 0 0 0 1 0 0 0 Next Status Vector Expected 0001 0100 0001 0000 0100 0000 0100 1110 0000 1110 1110 1110
ACK
0 Slave Transmitter 0100 0 0 0101
0 0
0 1
A slave byte was transmitted; No action required (expecting NACK received. STOP condition). A slave byte was transmitted; Load SMB0DAT with next data ACK received. byte to transmit. A Slave byte was transmitted; No action required (expecting error detected. Master to end transfer).
0 0 0 0 0
0X 0X 0X 0X 0 0 0 0 0 0 0
1X
An illegal STOP or bus error Clear STO. 0 X X was detected while a Slave Transmission was in progress. If Write, Acknowledge received address 1 0X A slave address + R/W was received; ACK requested.
If Read, Load SMB0DAT with 0 data byte; ACK received address NACK received address. 0 0 If Write, Acknowledge received address
0010 Slave Receiver
1
If Read, Load SMB0DAT with Lost arbitration as master; 0 1 X slave address + R/W received; data byte; ACK received address ACK requested. NACK received address. 0 Reschedule failed transfer; NACK received address. 1 0 0 0 0 0 1 0 1 0 1
0 0001 1
A STOP was detected while 0 X addressed as a Slave Transmitter or Slave Receiver. 1X
Clear STO.
0X 0 0 0
Lost arbitration while attempt- No action required (transfer complete/aborted). ing a STOP. Acknowledge received byte; Read SMB0DAT. NACK received byte.
0000 Bus Error Condition
1
A slave byte was received; 0X ACK requested. 1X 1X 1X
0010 0001 0000
0 0 1
Lost arbitration while attempt- Abort failed transfer. ing a repeated START. Reschedule failed transfer. Lost arbitration due to a detected STOP. Abort failed transfer. Reschedule failed transfer.
0X 0X 0X 0X 0 0
Lost arbitration while transmit- Abort failed transfer. ting a data byte as master. Reschedule failed transfer.
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Table 22.6. SMBus Status Decoding With Hardware ACK Generation Enabled (EHACK = 1)
Values to Write ACK 1 1 0 0 0 0 0 Current SMbus State Typical Response Options STO STA Next Status Vector Expected 1100 1110 1100 1110 1000 1000 1000 1110 1100 1110 1110 1100
245
Values Read Mode ARBLOST ACKRQ Status Vector
ACK
1110
0 0
0X 0
A master START was generated.
Load slave address + R/W into SMB0DAT.
0 1 0 0 0
0X 0X 1X 0X 1X 1X 0X 0
Master Transmitter
A master data or address byte Set STA to restart transfer. 0 was transmitted; NACK Abort transfer. received. Load next data byte into SMB0DAT. End transfer with STOP.
1100 0 0
End transfer with STOP and start A master data or address byte 1 another transfer. 1 was transmitted; ACK Send repeated START. 1 received. Switch to Master Receiver Mode (clear SI without writing new data 0 to SMB0DAT). Set ACK for initial data byte. Set ACK for next data byte; Read SMB0DAT. Set NACK to indicate next data byte as the last data byte; Read SMB0DAT. Initiate repeated START. 0 0 1
0 0 0
0 Master Receiver
0
A master data byte was 1 received; ACK sent.
1000
Switch to Master Transmitter Mode (write to SMB0DAT before 0 clearing SI). Read SMB0DAT; send STOP. A master data byte was 0 received; NACK sent (last byte). Read SMB0DAT; Send STOP followed by START. Initiate repeated START. 0 1 1
0X 1 1 0
0
0
Switch to Master Transmitter Mode (write to SMB0DAT before 0 clearing SI).
0X
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Table 22.6. SMBus Status Decoding With Hardware ACK Generation Enabled (EHACK = 1) (Continued)
Values Read Mode ARBLOST ACKRQ Status Vector Current SMbus State Typical Response Options STO STA Values to Write ACK 1 1 0 1 0 Next Status Vector Expected 0001 0100 0001 0000 0100 0000 0100 1110 0000 0000 1110 1110 1110
ACK
0 Slave Transmitter 0100 0 0 0101
0 0
0 1
A slave byte was transmitted; No action required (expecting NACK received. STOP condition). A slave byte was transmitted; Load SMB0DAT with next data ACK received. byte to transmit. A Slave byte was transmitted; No action required (expecting error detected. Master to end transfer).
0 0 0 0 0 0 0 0 1 0 0 0 0 0 1 0 1 0 1
0X 0X 0X 0X 0
1X
An illegal STOP or bus error Clear STO. 0 X X was detected while a Slave Transmission was in progress. A slave address + R/W was received; ACK sent. If Write, Set ACK for first data byte. If Read, Load SMB0DAT with data byte If Write, Set ACK for first data byte.
0
0X
0X 0
0010 Slave Receiver 0
Lost arbitration as master; 1 X slave address + R/W received; If Read, Load SMB0DAT with ACK sent. data byte Reschedule failed transfer A STOP was detected while 0 X addressed as a Slave Transmitter or Slave Receiver. 1X
0X 0X 0X 0 0 0
0 0001 0
Clear STO.
Lost arbitration while attempt- No action required (transfer complete/aborted). ing a STOP. Set ACK for next data byte; Read SMB0DAT. Set NACK for next data byte; Read SMB0DAT.
0000
0
0 X A slave byte was received.
Bus Error Condition
0010 0001 0000
0 0 0
1X 1X 1X
Lost arbitration while attempt- Abort failed transfer. ing a repeated START. Reschedule failed transfer. Lost arbitration due to a detected STOP. Abort failed transfer. Reschedule failed transfer.
0X 0X 0X 0X 0X 0X
Lost arbitration while transmit- Abort failed transfer. ting a data byte as master. Reschedule failed transfer.
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23. UART0
UART0 is an asynchronous, full duplex serial port offering modes 1 and 3 of the standard 8051 UART. Enhanced baud rate support allows a wide range of clock sources to generate standard baud rates (details in Section "23.1. Enhanced Baud Rate Generation" on page 248). Received data buffering allows UART0 to start reception of a second incoming data byte before software has finished reading the previous data byte. UART0 has two associated SFRs: Serial Control Register 0 (SCON0) and Serial Data Buffer 0 (SBUF0). The single SBUF0 location provides access to both transmit and receive registers. Writes to SBUF0 always access the Transmit register. Reads of SBUF0 always access the buffered Receive register; it is not possible to read data from the Transmit register. With UART0 interrupts enabled, an interrupt is generated each time a transmit is completed (TI0 is set in SCON0), or a data byte has been received (RI0 is set in SCON0). The UART0 interrupt flags are not cleared by hardware when the CPU vectors to the interrupt service routine. They must be cleared manually by software, allowing software to determine the cause of the UART0 interrupt (transmit complete or receive complete).
SFR Bus
Write to SBUF TB8
SET D CLR Q
SBUF (TX Shift)
TX
Crossbar
Zero Detector
Stop Bit Start Tx Clock
Shift
Data
Tx Control
Tx IRQ Send
SCON SMODE MCE REN TB8 RB8 TI RI UART Baud Rate Generator
TI Serial Port Interrupt RI
Port I/O
Rx IRQ Rx Clock
Rx Control
Start Shift 0x1FF RB8 Load SBUF
Input Shift Register (9 bits)
Load SBUF
SBUF (RX Latch)
Read SBUF
SFR Bus
RX
Crossbar
Figure 23.1. UART0 Block Diagram
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23.1. Enhanced Baud Rate Generation
The UART0 baud rate is generated by Timer 1 in 8-bit auto-reload mode. The TX clock is generated by TL1; the RX clock is generated by a copy of TL1 (shown as RX Timer in Figure 23.2), which is not useraccessible. Both TX and RX Timer overflows are divided by two to generate the TX and RX baud rates. The RX Timer runs when Timer 1 is enabled, and uses the same reload value (TH1). However, an RX Timer reload is forced when a START condition is detected on the RX pin. This allows a receive to begin any time a START is detected, independent of the TX Timer state.
Timer 1 TL1
Overflow
UART
2
TX Clock
TH1
Start Detected
RX Timer
Overflow
2
RX Clock
Figure 23.2. UART0 Baud Rate Logic
Timer 1 should be configured for Mode 2, 8-bit auto-reload (see Section "25.1.3. Mode 2: 8-bit Counter/Timer with Auto-Reload" on page 274). The Timer 1 reload value should be set so that overflows will occur at two times the desired UART baud rate frequency. Note that Timer 1 may be clocked by one of six sources: SYSCLK, SYSCLK / 4, SYSCLK / 12, SYSCLK / 48, the external oscillator clock / 8, or an external input T1. For any given Timer 1 clock source, the UART0 baud rate is determined by Equation 23.1-A and Equation 23.1-B. A)
1 UartBaudRate = -- T1_Overflow_Rate 2 T1 CLK T1_Overflow_Rate = ------------------------256 - TH1
Equation 23.1. UART0 Baud Rate
B)
Where T1CLK is the frequency of the clock supplied to Timer 1, and T1H is the high byte of Timer 1 (reload value). Timer 1 clock frequency is selected as described in Section "25.1. Timer 0 and Timer 1" on page 272. A quick reference for typical baud rates and system clock frequencies is given in Table 23.1 through Table 23.2. Note that the internal oscillator may still generate the system clock when the external oscillator is driving Timer 1.
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23.2. Operational Modes
UART0 provides standard asynchronous, full duplex communication. The UART mode (8-bit or 9-bit) is selected by the S0MODE bit (SCON0.7). Typical UART connection options are shown below.
RS-232
RS-232 LEVEL XLTR
TX RX
C8051Fxxx
OR
TX TX
MCU
RX RX
C8051Fxxx
Figure 23.3. UART Interconnect Diagram 23.2.1. 8-Bit UART
8-Bit UART mode uses a total of 10 bits per data byte: one start bit, eight data bits (LSB first), and one stop bit. Data are transmitted LSB first from the TX0 pin and received at the RX0 pin. On receive, the eight data bits are stored in SBUF0 and the stop bit goes into RB80 (SCON0.2). Data transmission begins when software writes a data byte to the SBUF0 register. The TI0 Transmit Interrupt Flag (SCON0.1) is set at the end of the transmission (the beginning of the stop-bit time). Data reception can begin any time after the REN0 Receive Enable bit (SCON0.4) is set to logic 1. After the stop bit is received, the data byte will be loaded into the SBUF0 receive register if the following conditions are met: RI0 must be logic 0, and if MCE0 is logic 1, the stop bit must be logic 1. In the event of a receive data overrun, the first received 8 bits are latched into the SBUF0 receive register and the following overrun data bits are lost. If these conditions are met, the eight bits of data is stored in SBUF0, the stop bit is stored in RB80 and the RI0 flag is set. If these conditions are not met, SBUF0 and RB80 will not be loaded and the RI0 flag will not be set. An interrupt will occur if enabled when either TI0 or RI0 is set.
MARK SPACE BIT TIMES
START BIT
D0
D1
D2
D3
D4
D5
D6
D7
STOP BIT
BIT SAMPLING
Figure 23.4. 8-Bit UART Timing Diagram
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23.2.2. 9-Bit UART
9-bit UART mode uses a total of eleven bits per data byte: a start bit, 8 data bits (LSB first), a programmable ninth data bit, and a stop bit. The state of the ninth transmit data bit is determined by the value in TB80 (SCON0.3), which is assigned by user software. It can be assigned the value of the parity flag (bit P in register PSW) for error detection, or used in multiprocessor communications. On receive, the ninth data bit goes into RB80 (SCON0.2) and the stop bit is ignored. Data transmission begins when an instruction writes a data byte to the SBUF0 register. The TI0 Transmit Interrupt Flag (SCON0.1) is set at the end of the transmission (the beginning of the stop-bit time). Data reception can begin any time after the REN0 Receive Enable bit (SCON0.4) is set to 1. After the stop bit is received, the data byte will be loaded into the SBUF0 receive register if the following conditions are met: (1) RI0 must be logic 0, and (2) if MCE0 is logic 1, the 9th bit must be logic 1 (when MCE0 is logic 0, the state of the ninth data bit is unimportant). If these conditions are met, the eight bits of data are stored in SBUF0, the ninth bit is stored in RB80, and the RI0 flag is set to 1. If the above conditions are not met, SBUF0 and RB80 will not be loaded and the RI0 flag will not be set to 1. A UART0 interrupt will occur if enabled when either TI0 or RI0 is set to 1.
MARK SPACE BIT TIMES START BIT
D0
D1
D2
D3
D4
D5
D6
D7
D8
STOP BIT
BIT SAMPLING
Figure 23.5. 9-Bit UART Timing Diagram
23.3. Multiprocessor Communications
9-Bit UART mode supports multiprocessor communication between a master processor and one or more slave processors by special use of the ninth data bit. When a master processor wants to transmit to one or more slaves, it first sends an address byte to select the target(s). An address byte differs from a data byte in that its ninth bit is logic 1; in a data byte, the ninth bit is always set to logic 0. Setting the MCE0 bit (SCON0.5) of a slave processor configures its UART such that when a stop bit is received, the UART will generate an interrupt only if the ninth bit is logic 1 (RB80 = 1) signifying an address byte has been received. In the UART interrupt handler, software will compare the received address with the slave's own assigned 8-bit address. If the addresses match, the slave will clear its MCE0 bit to enable interrupts on the reception of the following data byte(s). Slaves that weren't addressed leave their MCE0 bits set and do not generate interrupts on the reception of the following data bytes, thereby ignoring the data. Once the entire message is received, the addressed slave resets its MCE0 bit to ignore all transmissions until it receives the next address byte. Multiple addresses can be assigned to a single slave and/or a single address can be assigned to multiple slaves, thereby enabling "broadcast" transmissions to more than one slave simultaneously. The master processor can be configured to receive all transmissions or a protocol can be implemented such that the master/slave role is temporarily reversed to enable half-duplex transmission between the original master and slave(s).
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Master Device
RX TX
Slave Device
RX TX
Slave Device
RX TX
Slave Device
V+ RX TX
Figure 23.6. UART Multi-Processor Mode Interconnect Diagram
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SFR Definition 23.1. SCON0: Serial Port 0 Control
Bit Name Type Reset 7 S0MODE R/W 0 R 1 6 5 MCE0 R/W 0 4 REN0 R/W 0 3 TB80 R/W 0 2 RB80 R/W 0 1 TI0 R/W 0 0 RI0 R/W 0
SFR Page = 0x0; SFR Address = 0x98; Bit-Addressable Bit 7 Name Function
S0MODE Serial Port 0 Operation Mode. Selects the UART0 Operation Mode. 0: 8-bit UART with Variable Baud Rate. 1: 9-bit UART with Variable Baud Rate. Unused MCE0 Unused. Read = 1b. Write = Don't Care. Multiprocessor Communication Enable. For Mode 0 (8-bit UART): Checks for valid stop bit. 0: Logic level of stop bit is ignored. 1: RI0 will only be activated if stop bit is logic level 1. For Mode 1 (9-bit UART): Multiprocessor Communications Enable. 0: Logic level of ninth bit is ignored. 1: RI0 is set and an interrupt is generated only when the ninth bit is logic 1.
6 5
4
REN0
Receive Enable. 0: UART0 reception disabled. 1: UART0 reception enabled.
3
TB80
Ninth Transmission Bit. The logic level of this bit will be sent as the ninth transmission bit in 9-bit UART Mode (Mode 1). Unused in 8-bit mode (Mode 0).
2
RB80
Ninth Receive Bit. RB80 is assigned the value of the STOP bit in Mode 0; it is assigned the value of the 9th data bit in Mode 1.
1
TI0
Transmit Interrupt Flag. Set by hardware when a byte of data has been transmitted by UART0 (after the 8th bit in 8-bit UART Mode, or at the beginning of the STOP bit in 9-bit UART Mode). When the UART0 interrupt is enabled, setting this bit causes the CPU to vector to the UART0 interrupt service routine. This bit must be cleared manually by software.
0
RI0
Receive Interrupt Flag. Set to 1 by hardware when a byte of data has been received by UART0 (set at the STOP bit sampling time). When the UART0 interrupt is enabled, setting this bit to 1 causes the CPU to vector to the UART0 interrupt service routine. This bit must be cleared manually by software.
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SFR Definition 23.2. SBUF0: Serial (UART0) Port Data Buffer
Bit Name Type Reset R/W 0 R/W 0 R/W 0 7 6 5 4 3 2 1 0
SBUF0[7:0] R/W 0 R/W 0 R/W 0 R/W 0 R/W 0
SFR Page = 0x0; SFR Address = 0x99 Bit 7:0 Name SBUF0 Function Serial Data Buffer Bits 7:0 (MSB-LSB). This SFR accesses two registers; a transmit shift register and a receive latch register. When data is written to SBUF0, it goes to the transmit shift register and is held for serial transmission. Writing a byte to SBUF0 initiates the transmission. A read of SBUF0 returns the contents of the receive latch.
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Table 23.1. Timer Settings for Standard Baud Rates Using The Internal 24.5 MHz Oscillator
Target Baud Rate (bps) 230400 115200 57600 28800 14400 9600 2400 1200 Baud Rate % Error -0.32% -0.32% 0.15% -0.32% 0.15% -0.32% -0.32% 0.15% Frequency: 24.5 MHz Oscilla- Timer Clock SCA1-SCA0 tor Divide Source (pre-scale Factor select)1 106 SYSCLK XX2 212 SYSCLK XX 426 SYSCLK XX 848 SYSCLK/4 01 1704 SYSCLK/12 00 2544 SYSCLK/12 00 10176 SYSCLK/48 10 20448 SYSCLK/48 10 T1M1 Timer 1 Reload Value (hex) 0xCB 0x96 0x2B 0x96 0xB9 0x96 0x96 0x2B
1 1 1 0 0 0 0 0
Notes: 1. SCA1-SCA0 and T1M bit definitions can be found in Section 25.1. 2. X = Don't care.
SYSCLK from Internal Osc.
Table 23.2. Timer Settings for Standard Baud Rates Using an External 22.1184 MHz Oscillator
Target Baud Rate (bps) 230400 115200 57600 28800 14400 9600 2400 1200 230400 115200 57600 28800 14400 9600 Baud Rate % Error 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Frequency: 22.1184 MHz Oscilla- Timer Clock SCA1-SCA0 tor Divide Source (pre-scale Factor select)1 96 SYSCLK XX2 192 SYSCLK XX 384 SYSCLK XX 768 SYSCLK / 12 00 1536 SYSCLK / 12 00 2304 SYSCLK / 12 00 9216 SYSCLK / 48 10 18432 SYSCLK / 48 10 96 EXTCLK / 8 11 192 EXTCLK / 8 11 384 EXTCLK / 8 11 768 EXTCLK / 8 11 1536 EXTCLK / 8 11 2304 EXTCLK / 8 11 T1M1 Timer 1 Reload Value (hex) 0xD0 0xA0 0x40 0xE0 0xC0 0xA0 0xA0 0x40 0xFA 0xF4 0xE8 0xD0 0xA0 0x70
1 1 1 0 0 0 0 0 0 0 0 0 0 0
Notes: 1. SCA1-SCA0 and T1M bit definitions can be found in Section 25.1. 2. X = Don't care.
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SYSCLK from Internal Osc.
SYSCLK from External Osc.
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24. Enhanced Serial Peripheral Interface (SPI0 and SPI1)
The enhanced serial peripheral interfaces (SPI0 and SPI1) provide access to two identical, flexible, fullduplex synchronous serial busses. Both SPI0 and SPI1 will be referred to collectively as SPIn. SPIn can operate as a master or slave device in both 3-wire or 4-wire modes, and supports multiple masters and slaves on a single SPI bus. The slave-select (NSS) signal can be configured as an input to select SPIn in slave mode, or to disable Master Mode operation in a multi-master environment, avoiding contention on the SPI bus when more than one master attempts simultaneous data transfers. NSS can also be configured as a chip-select output in master mode, or disabled for 3-wire operation. Additional general purpose port I/O pins can be used to select multiple slave devices in master mode.
SFR Bus
SPInCKR
SCR7 SCR6 SCR5 SCR4 SCR3 SCR2 SCR1 SCR0
SPInCFG
SPIBSY MSTEN CKPHA CKPOL SLVSEL NSSIN SRMT RXBMT
SPInCN
SPIFn WCOLn MODFn RXOVRNn NSSnMD1 NSSnMD0 TXBMTn SPInEN
SYSCLK
Clock Divide Logic
SPI CONTROL LOGIC
Data Path Control Pin Interface Control
SPIn IRQ
Tx Data
MOSI
SPInDAT Transmit Data Buffer Pin Control Logic
SCK
Shift Register
76543210
Rx Data
MISO
C R O S S B A R
Port I/O
Receive Data Buffer
NSS
Write SPI0DAT
Read SPI0DAT
SFR Bus
Figure 24.1. SPI Block Diagram
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24.1. Signal Descriptions
The four signals used by each SPIn (MOSI, MISO, SCK, NSS) are described below.
24.1.1. Master Out, Slave In (MOSI)
The master-out, slave-in (MOSI) signal is an output from a master device and an input to slave devices. It is used to serially transfer data from the master to the slave. This signal is an output when SPIn is operating as a master anSPInd an input when SPIn is operating as a slave. Data is transferred most-significant bit first. When configured as a master, MOSI is driven by the MSB of the shift register in both 3- and 4-wire mode.
24.1.2. Master In, Slave Out (MISO)
The master-in, slave-out (MISO) signal is an output from a slave device and an input to the master device. It is used to serially transfer data from the slave to the master. This signal is an input when SPIn is operating as a master and an output when SPIn is operating as a slave. Data is transferred most-significant bit first. The MISO pin is placed in a high-impedance state when the SPI module is disabled and when the SPI operates in 4-wire mode as a slave that is not selected. When acting as a slave in 3-wire mode, MISO is always driven by the MSB of the shift register.
24.1.3. Serial Clock (SCK)
The serial clock (SCK) signal is an output from the master device and an input to slave devices. It is used to synchronize the transfer of data between the master and slave on the MOSI and MISO lines. SPIn generates this signal when operating as a master. The SCK signal is ignored by a SPI slave when the slave is not selected (NSS = 1) in 4-wire slave mode.
24.1.4. Slave Select (NSS)
The function of the slave-select (NSS) signal is dependent on the setting of the NSSnMD1 and NSSnMD0 bits in the SPInCN register. There are three possible modes that can be selected with these bits: 1. NSSMD[1:0] = 00: 3-Wire Master or 3-Wire Slave Mode: SPIn operates in 3-wire mode, and NSS is disabled. When operating as a slave device, SPIn is always selected in 3-wire mode. Since no select signal is present, SPIn must be the only slave on the bus in 3-wire mode. This is intended for point-to-point communication between a master and one slave. 2. NSSMD[1:0] = 01: 4-Wire Slave or Multi-Master Mode: SPIn operates in 4-wire mode, and NSS is enabled as an input. When operating as a slave, NSS selects the SPIn device. When operating as a master, a 1-to-0 transition of the NSS signal disables the master function of SPIn so that multiple master devices can be used on the same SPI bus. 3. NSSMD[1:0] = 1x: 4-Wire Master Mode: SPIn operates in 4-wire mode, and NSS is enabled as an output. The setting of NSSMD0 determines what logic level the NSS pin will output. This configuration should only be used when operating SPIn as a master device. See Figure 24.2, Figure 24.3, and Figure 24.4 for typical connection diagrams of the various operational modes. The setting of NSSMD bits affects the pinout of the device. When in 3-wire master or 3-wire slave mode, the NSS pin will not be mapped by the crossbar. In all other modes, the NSS signal will be mapped to a pin on the device. See Section "21. Port Input/Output" on page 205 for general purpose port I/ O and crossbar information.
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24.2. SPI Master Mode Operation
A SPI master device initiates all data transfers on a SPI bus. SPIn is placed in master mode by setting the Master Enable flag (MSTENn, SPInCN.6). Writing a byte of data to the SPIn data register (SPInDAT) when in master mode writes to the transmit buffer. If the SPI shift register is empty, the byte in the transmit buffer is moved to the shift register, and a data transfer begins. The SPIn master immediately shifts out the data serially on the MOSI line while providing the serial clock on SCK. The SPIFn (SPInCN.7) flag is set to logic 1 at the end of the transfer. If interrupts are enabled, an interrupt request is generated when the SPIF flag is set. While the SPIn master transfers data to a slave on the MOSI line, the addressed SPI slave device simultaneously transfers the contents of its shift register to the SPI master on the MISO line in a full-duplex operation. Therefore, the SPIF flag serves as both a transmit-complete and receive-data-ready flag. The data byte received from the slave is transferred MSB-first into the master's shift register. When a byte is fully shifted into the register, it is moved to the receive buffer where it can be read by the processor by reading SPInDAT. When configured as a master, SPIn can operate in one of three different modes: multi-master mode, 3-wire single-master mode, and 4-wire single-master mode. The default, multi-master mode is active when NSSnMD1 (SPInCN.3) = 0 and NSSnMD0 (SPInCN.2) = 1. In this mode, NSS is an input to the device, and is used to disable the master SPIn when another master is accessing the bus. When NSS is pulled low in this mode, MSTENn (SPInCN.6) and SPIENn (SPInCN.0) are set to 0 to disable the SPI master device, and a Mode Fault is generated (MODFn, SPInCN.5 = 1). Mode Fault will generate an interrupt if enabled. SPIn must be manually re-enabled in software under these circumstances. In multi-master systems, devices will typically default to being slave devices while they are not acting as the system master device. In multi-master mode, slave devices can be addressed individually (if needed) using general-purpose I/O pins. Figure 24.2 shows a connection diagram between two master devices in multiple-master mode. 3-wire single-master mode is active when NSSnMD1 (SPInCN.3) = 0 and NSSnMD0 (SPInCN.2) = 0. In this mode, NSS is not used, and is not mapped to an external port pin through the crossbar. Any slave devices that must be addressed in this mode should be selected using general-purpose I/O pins. Figure 24.3 shows a connection diagram between a master device in 3-wire master mode and a slave device. 4-wire single-master mode is active when NSSnMD1 (SPInCN.3) = 1. In this mode, NSS is configured as an output pin, and can be used as a slave-select signal for a single SPI device. In this mode, the output value of NSS is controlled (in software) with the bit NSSnMD0 (SPInCN.2). Additional slave devices can be addressed using general-purpose I/O pins. Figure 24.4 shows a connection diagram for a master device in 4-wire master mode and two slave devices.
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NSS
GPIO MISO MOSI SCK NSS
Master Device 1
MISO MOSI SCK GPIO
Master Device 2
Figure 24.2. Multiple-Master Mode Connection Diagram
Master Device
MISO MOSI SCK
MISO MOSI SCK
Slave Device
Figure 24.3. 3-Wire Single Master and 3-Wire Single Slave Mode Connection Diagram
Master Device
GPIO
MISO MOSI SCK NSS
MISO MOSI SCK NSS
Slave Device
MISO MOSI SCK NSS
Slave Device
Figure 24.4. 4-Wire Single Master Mode and 4-Wire Slave Mode Connection Diagram
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24.3. SPI Slave Mode Operation
When SPIn is enabled and not configured as a master, it will operate as a SPI slave. As a slave, bytes are shifted in through the MOSI pin and out through the MISO pin by a master device controlling the SCK signal. A bit counter in the SPIn logic counts SCK edges. When 8 bits have been shifted through the shift register, the SPIF flag is set to logic 1, and the byte is copied into the receive buffer. Data is read from the receive buffer by reading SPInDAT. A slave device cannot initiate transfers. Data to be transferred to the master device is pre-loaded into the shift register by writing to SPInDAT. Writes to SPInDAT are doublebuffered, and are placed in the transmit buffer first. If the shift register is empty, the contents of the transmit buffer will immediately be transferred into the shift register. When the shift register already contains data, the SPI will load the shift register with the transmit buffer's contents after the last SCK edge of the next (or current) SPI transfer. When configured as a slave, SPIn can be configured for 4-wire or 3-wire operation. The default, 4-wire slave mode, is active when NSSnMD1 (SPInCN.3) = 0 and NSSnMD0 (SPInCN.2) = 1. In 4-wire mode, the NSS signal is routed to a port pin and configured as a digital input. SPIn is enabled when NSS is logic 0, and disabled when NSS is logic 1. The bit counter is reset on a falling edge of NSS. Note that the NSS signal must be driven low at least 2 system clocks before the first active edge of SCK for each byte transfer. Figure 24.4 shows a connection diagram between two slave devices in 4-wire slave mode and a master device. 3-wire slave mode is active when NSSnMD1 (SPInCN.3) = 0 and NSSnMD0 (SPInCN.2) = 0. NSS is not used in this mode, and is not mapped to an external port pin through the crossbar. Since there is no way of uniquely addressing the device in 3-wire slave mode, SPIn must be the only slave device present on the bus. It is important to note that in 3-wire slave mode there is no external means of resetting the bit counter that determines when a full byte has been received. The bit counter can only be reset by disabling and reenabling SPIn with the SPIEN bit. Figure 24.3 shows a connection diagram between a slave device in 3wire slave mode and a master device.
24.4. SPI Interrupt Sources
When SPIn interrupts are enabled, the following four flags will generate an interrupt when they are set to logic 1: All of the following bits must be cleared by software. 1. The SPI Interrupt Flag, SPIFn (SPInCN.7) is set to logic 1 at the end of each byte transfer. This flag can occur in all SPIn modes. 2. The Write Collision Flag, WCOLn (SPInCN.6) is set to logic 1 if a write to SPInDAT is attempted when the transmit buffer has not been emptied to the SPI shift register. When this occurs, the write to SPInDAT will be ignored, and the transmit buffer will not be written.This flag can occur in all SPIn modes. 3. The Mode Fault Flag MODFn (SPInCN.5) is set to logic 1 when SPIn is configured as a master, and for multi-master mode and the NSS pin is pulled low. When a Mode Fault occurs, the MSTENn and SPIENn bits in SPI0CN are set to logic 0 to disable SPIn and allow another master device to access the bus. 4. The Receive Overrun Flag RXOVRNn (SPInCN.4) is set to logic 1 when configured as a slave, and a transfer is completed and the receive buffer still holds an unread byte from a previous transfer. The new byte is not transferred to the receive buffer, allowing the previously received data byte to be read. The data byte which caused the overrun is lost.
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24.5. Serial Clock Phase and Polarity
Four combinations of serial clock phase and polarity can be selected using the clock control bits in the SPI Configuration Register (SPInCFG). The CKPHA bit (SPInCFG.5) selects one of two clock phases (edge used to latch the data). The CKPOL bit (SPInCFG.4) selects between an active-high or active-low clock. Both master and slave devices must be configured to use the same clock phase and polarity. SPI0 should be disabled (by clearing the SPIENn bit, SPInCN.0) when changing the clock phase or polarity. The clock and data line relationships for master mode are shown in Figure 24.5. For slave mode, the clock and data relationships are shown in Figure 24.6 and Figure 24.7. Note that CKPHA must be set to 0 on both the master and slave SPI when communicating between two of the following devices: C8051F04x, C8051F06x, C8051F12x, C8051F31x, C8051F32x, and C8051F33x. The SPIn Clock Rate Register (SPInCKR) as shown in SFR Definition 24.3 controls the master mode serial clock frequency. This register is ignored when operating in slave mode. When the SPI is configured as a master, the maximum data transfer rate (bits/sec) is one-half the system clock frequency or 12.5 MHz, whichever is slower. When the SPI is configured as a slave, the maximum data transfer rate (bits/sec) for full-duplex operation is 1/10 the system clock frequency, provided that the master issues SCK, NSS (in 4wire slave mode), and the serial input data synchronously with the slave's system clock. If the master issues SCK, NSS, and the serial input data asynchronously, the maximum data transfer rate (bits/sec) must be less than 1/10 the system clock frequency. In the special case where the master only wants to transmit data to the slave and does not need to receive data from the slave (i.e. half-duplex operation), the SPI slave can receive data at a maximum data transfer rate (bits/sec) of 1/4 the system clock frequency. This is provided that the master issues SCK, NSS, and the serial input data synchronously with the slave's system clock.
SCK (CKPOL=0, CKPHA=0)
SCK (CKPOL=0, CKPHA=1)
SCK (CKPOL=1, CKPHA=0)
SCK (CKPOL=1, CKPHA=1)
MISO/MOSI
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
NSS (Must Remain High in Multi-Master Mode)
Figure 24.5. Master Mode Data/Clock Timing
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SCK (CKPOL=0, CKPHA=0)
SCK (CKPOL=1, CKPHA=0)
MOSI
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
MISO
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
NSS (4-Wire Mode)
Figure 24.6. Slave Mode Data/Clock Timing (CKPHA = 0)
SCK (CKPOL=0, CKPHA=1)
SCK (CKPOL=1, CKPHA=1)
MOSI
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
MISO
MSB
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
NSS (4-Wire Mode)
Figure 24.7. Slave Mode Data/Clock Timing (CKPHA = 1)
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24.6. SPI Special Function Registers
SPI0 and SPI1 are accessed and controlled through four special function registers (8 registers total) in the system controller: SPInCN Control Register, SPInDAT Data Register, SPInCFG Configuration Register, and SPInCKR Clock Rate Register. The special function registers related to the operation of the SPI0 and SPI1 Bus are described in the following figures.
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SFR Definition 24.1. SPInCFG: SPI Configuration
Bit Name Type Reset 7 SPIBSY R 0 6 MSTEN R/W 0 5 CKPHA R/W 0 4 CKPOL R/W 0 3 SLVSEL R 0 2 NSSIN R 1 1 SRMT R 1 0 RXBMT R 1
SFR Addresses: SPI0CFG = 0xA1, SPI1CFG = 0x84 SFR Pages: SPI0CFG = 0x0, SPI1CFG = 0x0 Bit Name 7 6 SPIBSY MSTEN SPI Busy.
Function
This bit is set to logic 1 when a SPI transfer is in progress (master or slave mode). Master Mode Enable. 0: Disable master mode. Operate in slave mode. 1: Enable master mode. Operate as a master. 5 CKPHA SPI Clock Phase. 0: Data centered on first edge of SCK period.* 1: Data centered on second edge of SCK period.* 4 CKPOL SPI Clock Polarity. 0: SCK line low in idle state. 1: SCK line high in idle state. 3 SLVSEL Slave Selected Flag. Set to logic 1 whenever the NSS pin is low indicating SPI0 is the selected slave. It is cleared to logic 0 when NSS is high (slave not selected). This bit does not indicate the instantaneous value at the NSS pin, but rather a de-glitched version of the pin input. 2 NSSIN NSS Instantaneous Pin Input. This bit mimics the instantaneous value that is present on the NSS port pin at the time that the register is read. This input is not de-glitched. 1 SRMT Shift Register Empty (valid in slave mode only). Set to logic 1 when data has been transferred in/out of the shift register, and there is no data is available to read from the transmit buffer or write to the receive buffer. Set to logic 0 when a data byte is transferred to the shift register from the transmit buffer or by a transition on SCK. Note: SRMT = 1 in Master Mode. 0 RXBMT Receive Buffer Empty (valid in slave mode only). Set to logic 1 when the receive buffer has been read and contains no new information. If there is new information available in the receive buffer that has not been read, this bit will return to logic 0. Note: RXBMT = 1 in Master Mode.
*Note: In slave mode, data on MOSI is sampled in the center of each data bit. In master mode, data on MISO is sampled one SYSCLK before the end of each data bit, to provide maximum settling time for the slave device. See Table 24.1 for timing parameters.
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SFR Definition 24.2. SPInCN: SPI Control
Bit Name Type Reset 7 SPIFn R/W 0 6 5 4 RXOVRNn R/W 0 3 NSSnMD1 R/W 0 2 NSSnMD0 R/W 1 1 TXBMTn R 1 0 SPInEN R/W 0
WCOLn MODFn R/W 0 R/W 0
SFR Addresses: SPI0CN = 0xF8, Bit-Addressable; SPI1CN = 0xB0, Bit-Addressable SFR Pages: SPI0CN = 0x0, SPI1CN = 0x0 Bit Name Function 7 SPIFn SPIn Interrupt Flag. This bit is set to logic 1 by hardware at the end of a data transfer. If interrupts are enabled, setting this bit causes the CPU to vector to the SPIn interrupt service routine. This bit is not automatically cleared by hardware. It must be cleared by software. 6 WCOLn Write Collision Flag. This bit is set to logic 1 by hardware (and generates a SPI0 interrupt) to indicate a write to the SPI0 data register was attempted while a data transfer was in progress. It must be cleared by software. 5 MODFn Mode Fault Flag. This bit is set to logic 1 by hardware (and generates a SPI0 interrupt) when a master mode collision is detected (NSS is low, MSTEN = 1, and NSSMD[1:0] = 01). This bit is not automatically cleared by hardware. It must be cleared by software. 4 RXOVRNn Receive Overrun Flag (valid in slave mode only). This bit is set to logic 1 by hardware (and generates a SPIn interrupt) when the receive buffer still holds unread data from a previous transfer and the last bit of the current transfer is shifted into the SPI shift register. This bit is not automatically cleared by hardware. It must be cleared by software. 3:2 NSSnMD[1:0] Slave Select Mode. Selects between the following NSS operation modes: (See Section 24.2 and Section 24.3). 00: 3-Wire Slave or 3-Wire Master Mode. NSS signal is not routed to a port pin. 01: 4-Wire Slave or Multi-Master Mode (Default). NSS is an input to the device. 1x: 4-Wire Single-Master Mode. NSS signal is mapped as an output from the device and will assume the value of NSSMD0. 1 TXBMTn Transmit Buffer Empty. This bit will be set to logic 0 when new data has been written to the transmit buffer. When data in the transmit buffer is transferred to the SPI shift register, this bit will be set to logic 1, indicating that it is safe to write a new byte to the transmit buffer. 0 SPInEN SPIn Enable. 0: SPIn disabled. 1: SPIn enabled.
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SFR Definition 24.3. SPInCKR: SPI Clock Rate
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 SCRn[7:0] R/W 0 0 0 0 2 1 0
SFR Addresses: SPI0CKR = 0xA2, SPI1CKR = 0x85 SFR Pages: SPI0CKR = 0x0, SPI1CKR = 0x0 Bit Name 7:0 SCRn SPI Clock Rate.
Function
These bits determine the frequency of the SCK output when the SPI module is configured for master mode operation. The SCK clock frequency is a divided version of the system clock, and is given in the following equation, where SYSCLK is the system clock frequency and SPInCKR is the 8-bit value held in the SPInCKR register.
SYSCLK f SCK = ---------------------------------------------------------2 SPInCKR[7:0] + 1
for 0 <= SPI0CKR <= 255 Example: If SYSCLK = 2 MHz and SPInCKR = 0x04,
2000000 f SCK = ------------------------2 4 + 1 f SCK = 200kHz
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SFR Definition 24.4. SPInDAT: SPI Data
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
SPInDAT[7:0] R/W 0 0 0 0
SFR Addresses: SPI0DAT = 0xA3, SPI1DAT = 0x86 SFR Pages: SPI0DAT = 0x0, SPI1DAT = 0x0 Bit Name 7:0 SPInDAT SPIn Transmit and Receive Data.
Function
The SPInDAT register is used to transmit and receive SPIn data. Writing data to SPInDAT places the data into the transmit buffer and initiates a transfer when in Master Mode. A read of SPInDAT returns the contents of the receive buffer.
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SCK* T T
MCKH
MCKL
T
MIS
T
MIH
MISO
MOSI
* SCK is shown for CKPOL = 0. SCK is the opposite polarity for CKPOL = 1.
Figure 24.8. SPI Master Timing (CKPHA = 0)
SCK* T T
MCKH
MCKL
T
MIS
T
MIH
MISO
MOSI
* SCK is shown for CKPOL = 0. SCK is the opposite polarity for CKPOL = 1.
Figure 24.9. SPI Master Timing (CKPHA = 1)
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NSS T T T
SE
CKL
SD
SCK* T
CKH
T
SIS
T
SIH
MOSI
T
SEZ
T
SOH
T
SDZ
MISO
* SCK is shown for CKPOL = 0. SCK is the opposite polarity for CKPOL = 1.
Figure 24.10. SPI Slave Timing (CKPHA = 0)
NSS T T T
SE
CKL
SD
SCK* T
CKH
T
SIS
T
SIH
MOSI
T
T
SEZ
SOH
T
SLH
T
SDZ
MISO
* SCK is shown for CKPOL = 0. SCK is the opposite polarity for CKPOL = 1.
Figure 24.11. SPI Slave Timing (CKPHA = 1)
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Table 24.1. SPI Slave Timing Parameters
Parameter Description Min Max Units Master Mode Timing* (See Figure 24.8 and Figure 24.9) TMCKH TMCKL TMIS TMIH SCK High Time SCK Low Time MISO Valid to SCK Shift Edge SCK Shift Edge to MISO Change 1 x TSYSCLK 1 x TSYSCLK 1 x TSYSCLK + 20 0 -- -- -- -- ns ns ns ns
Slave Mode Timing* (See Figure 24.10 and Figure 24.11) TSE TSD TSEZ TSDZ TCKH TCKL TSIS TSIH TSOH TSLH NSS Falling to First SCK Edge Last SCK Edge to NSS Rising NSS Falling to MISO Valid NSS Rising to MISO High-Z SCK High Time SCK Low Time MOSI Valid to SCK Sample Edge SCK Sample Edge to MOSI Change SCK Shift Edge to MISO Change Last SCK Edge to MISO Change (CKPHA = 1 ONLY) 2 x TSYSCLK 2 x TSYSCLK -- -- 5 x TSYSCLK 5 x TSYSCLK 2 x TSYSCLK 2 x TSYSCLK -- 6 x TSYSCLK -- -- 4 x TSYSCLK 4 x TSYSCLK -- -- -- -- 4 x TSYSCLK 8 x TSYSCLK ns ns ns ns ns ns ns ns ns ns
*Note: TSYSCLK is equal to one period of the device system clock (SYSCLK).
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25. Timers
Each MCU includes four counter/timers: two are 16-bit counter/timers compatible with those found in the standard 8051, and two are 16-bit auto-reload timer for use with the ADC, SMBus, or for general purpose use. These timers can be used to measure time intervals, count external events and generate periodic interrupt requests. Timer 0 and Timer 1 are nearly identical and have four primary modes of operation. Timer 2 and Timer 3 offer 16-bit and split 8-bit timer functionality with auto-reload. Additionally, Timer 2 and Timer 3 have a Capture Mode that can be used to measure the SmaRTClock or a Comparator period with respect to another oscillator. This is particularly useful when using Capacitive Touch Switches. See Application Note AN338 for details on Capacitive Touch Switch sensing. Timer 0 and Timer 1 Modes: 13-bit counter/timer 16-bit counter/timer 8-bit counter/timer with autoreload Two 8-bit counter/timers (Timer 0 only) Timer 2 Modes: 16-bit timer with auto-reload Timer 3 Modes: 16-bit timer with auto-reload
Two 8-bit timers with auto-reload
Two 8-bit timers with auto-reload
Timers 0 and 1 may be clocked by one of five sources, determined by the Timer Mode Select bits (T1M- T0M) and the Clock Scale bits (SCA1-SCA0). The Clock Scale bits define a pre-scaled clock from which Timer 0 and/or Timer 1 may be clocked (See SFR Definition 25.1 for pre-scaled clock selection). Timer 0/1 may then be configured to use this pre-scaled clock signal or the system clock. Timer 2 and Timer 3 may be clocked by the system clock, the system clock divided by 12. Timer 2 may additionally be clocked by the SmaRTClock divided by 8 or the Comparator0 output. Timer 3 may additionally be clocked by the external oscillator clock source divided by 8 or the Comparator1 output. Timer 0 and Timer 1 may also be operated as counters. When functioning as a counter, a counter/timer register is incremented on each high-to-low transition at the selected input pin (T0 or T1). Events with a frequency of up to one-fourth the system clock frequency can be counted. The input signal need not be periodic, but it should be held at a given level for at least two full system clock cycles to ensure the level is properly sampled.
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SFR Definition 25.1. CKCON: Clock Control
Bit Name Type Reset 7 T3MH R/W 0 6 T3ML R/W 0 5 T2MH R/W 0 4 T2ML R/W 0 3 T1M R/W 0 2 T0M R/W 0 0 1 SCA[1:0] R/W 0 0
SFR Page = 0x0; SFR Address = 0x8E Bit Name 7 T3MH Timer 3 High Byte Clock Select.
Function
Selects the clock supplied to the Timer 3 high byte (split 8-bit timer mode only). 0: Timer 3 high byte uses the clock defined by the T3XCLK bit in TMR3CN. 1: Timer 3 high byte uses the system clock. 6 T3ML Timer 3 Low Byte Clock Select. Selects the clock supplied to Timer 3. Selects the clock supplied to the lower 8-bit timer in split 8-bit timer mode. 0: Timer 3 low byte uses the clock defined by the T3XCLK bit in TMR3CN. 1: Timer 3 low byte uses the system clock. 5 T2MH Timer 2 High Byte Clock Select. Selects the clock supplied to the Timer 2 high byte (split 8-bit timer mode only). 0: Timer 2 high byte uses the clock defined by the T2XCLK bit in TMR2CN. 1: Timer 2 high byte uses the system clock. 4 T2ML Timer 2 Low Byte Clock Select. Selects the clock supplied to Timer 2. If Timer 2 is configured in split 8-bit timer mode, this bit selects the clock supplied to the lower 8-bit timer. 0: Timer 2 low byte uses the clock defined by the T2XCLK bit in TMR2CN. 1: Timer 2 low byte uses the system clock. 3 T1M Timer 1 Clock Select. Selects the clock source supplied to Timer 1. Ignored when C/T1 is set to 1. 0: Timer 1 uses the clock defined by the prescale bits SCA[1:0]. 1: Timer 1 uses the system clock. 2 T0M Timer 0 Clock Select. Selects the clock source supplied to Timer 0. Ignored when C/T0 is set to 1. 0: Counter/Timer 0 uses the clock defined by the prescale bits SCA[1:0]. 1: Counter/Timer 0 uses the system clock. 1:0 SCA[1:0] Timer 0/1 Prescale Bits. These bits control the Timer 0/1 Clock Prescaler: 00: System clock divided by 12 01: System clock divided by 4 10: System clock divided by 48 11: External clock divided by 8 (synchronized with the system clock)
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25.1. Timer 0 and Timer 1
Each timer is implemented as a 16-bit register accessed as two separate bytes: a low byte (TL0 or TL1) and a high byte (TH0 or TH1). The Counter/Timer Control register (TCON) is used to enable Timer 0 and Timer 1 as well as indicate status. Timer 0 interrupts can be enabled by setting the ET0 bit in the IE register (Section "12.5. Interrupt Register Descriptions" on page 123); Timer 1 interrupts can be enabled by setting the ET1 bit in the IE register (Section "12.5. Interrupt Register Descriptions" on page 123). Both counter/timers operate in one of four primary modes selected by setting the Mode Select bits T1M1-T0M0 in the Counter/Timer Mode register (TMOD). Each timer can be configured independently. Each operating mode is described below.
25.1.1. Mode 0: 13-bit Counter/Timer
Timer 0 and Timer 1 operate as 13-bit counter/timers in Mode 0. The following describes the configuration and operation of Timer 0. However, both timers operate identically, and Timer 1 is configured in the same manner as described for Timer 0. The TH0 register holds the eight MSBs of the 13-bit counter/timer. TL0 holds the five LSBs in bit positions TL0.4-TL0.0. The three upper bits of TL0 (TL0.7-TL0.5) are indeterminate and should be masked out or ignored when reading. As the 13-bit timer register increments and overflows from 0x1FFF (all ones) to 0x0000, the timer overflow flag TF0 (TCON.5) is set and an interrupt will occur if Timer 0 interrupts are enabled. The C/T0 bit (TMOD.2) selects the counter/timer's clock source. When C/T0 is set to logic 1, high-to-low transitions at the selected Timer 0 input pin (T0) increment the timer register (Refer to Section "21.3. Priority Crossbar Decoder" on page 209 for information on selecting and configuring external I/O pins). Clearing C/T selects the clock defined by the T0M bit (CKCON.3). When T0M is set, Timer 0 is clocked by the system clock. When T0M is cleared, Timer 0 is clocked by the source selected by the Clock Scale bits in CKCON (see SFR Definition 25.1). Setting the TR0 bit (TCON.4) enables the timer when either GATE0 (TMOD.3) is logic 0 or the input signal INT0 is active as defined by bit IN0PL in register IT01CF (see SFR Definition 12.7). Setting GATE0 to 1 allows the timer to be controlled by the external input signal INT0 (see Section "12.5. Interrupt Register Descriptions" on page 123), facilitating pulse width measurements
Table 25.1. Timer 0 Running Modes
TR0 0 1 1 1
Note: X = Don't Care
GATE0 X 0 1 1
INT0 X X 0 1
Counter/Timer Disabled Enabled Disabled Enabled
Setting TR0 does not force the timer to reset. The timer registers should be loaded with the desired initial value before the timer is enabled. TL1 and TH1 form the 13-bit register for Timer 1 in the same manner as described above for TL0 and TH0. Timer 1 is configured and controlled using the relevant TCON and TMOD bits just as with Timer 0. The input signal INT1 is used with Timer 1; the INT1 polarity is defined by bit IN1PL in register IT01CF (see SFR Definition 12.7).
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CKCON
T 3 M H T 3 M L T 2 M H TTTSS 2 1 0CC MMMA A 10 L
G A T E 1 C / T 1
TM OD
T 1 M 1 T 1 M 0 G A T E 0 C / T 0 T 0 M 1 T 0 M 0 I N 1 P L I N 1 S L 2
IT 0 1 C F
I N 1 S L 1 I N 1 S L 0 I N 0 P L I N 0 S L 2 I N 0 S L 1 I N 0 S L 0
P re -s ca le d C lo c k
0 0
SYSCLK
1 1
T0 TR0 G ATE0 C ro ss b a r
TCLK
IN T 0
IN 0 P L
XOR
Figure 25.1. T0 Mode 0 Block Diagram 25.1.2. Mode 1: 16-bit Counter/Timer
Mode 1 operation is the same as Mode 0, except that the counter/timer registers use all 16 bits. The counter/timers are enabled and configured in Mode 1 in the same manner as for Mode 0.
Rev. 1.0
TCON
TL0 (5 b its )
TH0 (8 b its)
TF1 TR1 TF0 TR0 IE 1 IT 1 IE 0 IT 0
Inte rru pt
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25.1.3. Mode 2: 8-bit Counter/Timer with Auto-Reload
Mode 2 configures Timer 0 and Timer 1 to operate as 8-bit counter/timers with automatic reload of the start value. TL0 holds the count and TH0 holds the reload value. When the counter in TL0 overflows from all ones to 0x00, the timer overflow flag TF0 (TCON.5) is set and the counter in TL0 is reloaded from TH0. If Timer 0 interrupts are enabled, an interrupt will occur when the TF0 flag is set. The reload value in TH0 is not changed. TL0 must be initialized to the desired value before enabling the timer for the first count to be correct. When in Mode 2, Timer 1 operates identically to Timer 0. Both counter/timers are enabled and configured in Mode 2 in the same manner as Mode 0. Setting the TR0 bit (TCON.4) enables the timer when either GATE0 (TMOD.3) is logic 0 or when the input signal INT0 is active as defined by bit IN0PL in register IT01CF (see Section "12.6. External Interrupts INT0 and INT1" on page 130 for details on the external input signals INT0 and INT1).
CKCON
TTTTTTS 332210C MMMMMMA HLHL 1 S C A 0
G A T E 1 C / T 1
TMOD
T 1 M 1 T 1 M 0 G A T E 0 C / T 0 T 0 M 1 T 0 M 0 I N 1 P L I N 1 S L 2
IT01CF
I N 1 S L 1 I N 1 S L 0 I N 0 P L I N 0 S L 2 I N 0 S L 1 I N 0 S L 0
Pre-scaled Clock
0 0
SYSCLK
1 1
T0
TCLK
TL0 (8 bits) TCON
TR0 Crossbar GATE0 TH0 (8 bits) INT0 IN0PL
XOR
TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0
Interrupt
Reload
Figure 25.2. T0 Mode 2 Block Diagram
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25.1.4. Mode 3: Two 8-bit Counter/Timers (Timer 0 Only)
In Mode 3, Timer 0 is configured as two separate 8-bit counter/timers held in TL0 and TH0. The counter/timer in TL0 is controlled using the Timer 0 control/status bits in TCON and TMOD: TR0, C/T0, GATE0 and TF0. TL0 can use either the system clock or an external input signal as its timebase. The TH0 register is restricted to a timer function sourced by the system clock or prescaled clock. TH0 is enabled using the Timer 1 run control bit TR1. TH0 sets the Timer 1 overflow flag TF1 on overflow and thus controls the Timer 1 interrupt. Timer 1 is inactive in Mode 3. When Timer 0 is operating in Mode 3, Timer 1 can be operated in Modes 0, 1 or 2, but cannot be clocked by external signals nor set the TF1 flag and generate an interrupt. However, the Timer 1 overflow can be used to generate baud rates for the SMBus and/or UART, and/or initiate ADC conversions. While Timer 0 is operating in Mode 3, Timer 1 run control is handled through its mode settings. To run Timer 1 while Timer 0 is in Mode 3, set the Timer 1 Mode as 0, 1, or 2. To disable Timer 1, configure it for Mode 3.
CKCON
TTTTTTSS 3 3 2 2 1 0 CC MMMMMM A A HLHL 10
G A T E 1 C / T 1
TMOD
TTG 11A MM T 10E 0 C / T 0 TT 00 MM 10
Pre-scaled Clock
0 TR1 TH0 (8 bits) TCON
TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0
Interrupt Interrupt
SYSCLK
1 0
1 T0 TL0 (8 bits) TR0 Crossbar GATE0
INT0
IN0PL
XOR
Figure 25.3. T0 Mode 3 Block Diagram
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SFR Definition 25.2. TCON: Timer Control
Bit Name Type Reset 7 TF1 R/W 0 6 TR1 R/W 0 5 TF0 R/W 0 4 TR0 R/W 0 3 IE1 R/W 0 2 IT1 R/W 0 1 IE0 R/W 0 0 IT0 R/W 0
SFR Page = 0x0; SFR Address = 0x88; Bit-Addressable Bit Name Function 7 TF1 Timer 1 Overflow Flag. Set to 1 by hardware when Timer 1 overflows. This flag can be cleared by software but is automatically cleared when the CPU vectors to the Timer 1 interrupt service routine. 6 5 TR1 TF0 Timer 1 Run Control. Timer 1 is enabled by setting this bit to 1. Timer 0 Overflow Flag. Set to 1 by hardware when Timer 0 overflows. This flag can be cleared by software but is automatically cleared when the CPU vectors to the Timer 0 interrupt service routine. 4 3 TR0 IE1 Timer 0 Run Control. Timer 0 is enabled by setting this bit to 1. External Interrupt 1. This flag is set by hardware when an edge/level of type defined by IT1 is detected. It can be cleared by software but is automatically cleared when the CPU vectors to the External Interrupt 1 service routine in edge-triggered mode. 2 IT1 Interrupt 1 Type Select. This bit selects whether the configured INT1 interrupt will be edge or level sensitive. INT1 is configured active low or high by the IN1PL bit in the IT01CF register (see SFR Definition 12.7). 0: INT1 is level triggered. 1: INT1 is edge triggered. 1 IE0 External Interrupt 0. This flag is set by hardware when an edge/level of type defined by IT1 is detected. It can be cleared by software but is automatically cleared when the CPU vectors to the External Interrupt 0 service routine in edge-triggered mode. 0 IT0 Interrupt 0 Type Select. This bit selects whether the configured INT0 interrupt will be edge or level sensitive. INT0 is configured active low or high by the IN0PL bit in register IT01CF (see SFR Definition 12.7). 0: INT0 is level triggered. 1: INT0 is edge triggered.
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SFR Definition 25.3. TMOD: Timer Mode
Bit Name Type Reset 7 GATE1 R/W 0 6 C/T1 R/W 0 0 5 T1M[1:0] R/W 0 4 3 GATE0 R/W 0 2 C/T0 R/W 0 0 1 T0M[1:0] R/W 0 0
SFR Page = 0x0; SFR Address = 0x89 Bit Name 7 GATE1 Timer 1 Gate Control.
Function
0: Timer 1 enabled when TR1 = 1 irrespective of INT1 logic level. 1: Timer 1 enabled only when TR1 = 1 AND INT1 is active as defined by bit IN1PL in register IT01CF (see SFR Definition 12.7). 6 C/T1 Counter/Timer 1 Select. 0: Timer: Timer 1 incremented by clock defined by T1M bit in register CKCON. 1: Counter: Timer 1 incremented by high-to-low transitions on external pin (T1). 5:4 T1M[1:0] Timer 1 Mode Select. These bits select the Timer 1 operation mode. 00: Mode 0, 13-bit Counter/Timer 01: Mode 1, 16-bit Counter/Timer 10: Mode 2, 8-bit Counter/Timer with Auto-Reload 11: Mode 3, Timer 1 Inactive 3 GATE0 Timer 0 Gate Control. 0: Timer 0 enabled when TR0 = 1 irrespective of INT0 logic level. 1: Timer 0 enabled only when TR0 = 1 AND INT0 is active as defined by bit IN0PL in register IT01CF (see SFR Definition 12.7). 2 C/T0 Counter/Timer 0 Select. 0: Timer: Timer 0 incremented by clock defined by T0M bit in register CKCON. 1: Counter: Timer 0 incremented by high-to-low transitions on external pin (T0). 1:0 T0M[1:0] Timer 0 Mode Select. These bits select the Timer 0 operation mode. 00: Mode 0, 13-bit Counter/Timer 01: Mode 1, 16-bit Counter/Timer 10: Mode 2, 8-bit Counter/Timer with Auto-Reload 11: Mode 3, Two 8-bit Counter/Timers
Rev. 1.0
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C8051F91x-C8051F90x
SFR Definition 25.4. TL0: Timer 0 Low Byte
Bit Name Type Reset 0 0 0 0 7 6 5 4 TL0[7:0] R/W 0 0 0 0 3 2 1 0
SFR Page = 0x0; SFR Address = 0x8A Bit Name 7:0 TL0[7:0] Timer 0 Low Byte.
Function
The TL0 register is the low byte of the 16-bit Timer 0.
SFR Definition 25.5. TL1: Timer 1 Low Byte
Bit Name Type Reset 0 0 0 0 7 6 5 4 TL1[7:0] R/W 0 0 0 0 3 2 1 0
SFR Page = 0x0; SFR Address = 0x8B Bit Name 7:0 TL1[7:0] Timer 1 Low Byte.
Function
The TL1 register is the low byte of the 16-bit Timer 1.
278
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SFR Definition 25.6. TH0: Timer 0 High Byte
Bit Name Type Reset 0 0 0 0 7 6 5 4 TH0[7:0] R/W 0 0 0 0 3 2 1 0
SFR Page = 0x0; SFR Address = 0x8C Bit Name 7:0 TH0[7:0] Timer 0 High Byte.
Function
The TH0 register is the high byte of the 16-bit Timer 0.
SFR Definition 25.7. TH1: Timer 1 High Byte
Bit Name Type Reset 0 0 0 0 7 6 5 4 TH1[7:0] R/W 0 0 0 0 3 2 1 0
SFR Page = 0x0; SFR Address = 0x8D Bit Name 7:0 TH1[7:0] Timer 1 High Byte.
Function
The TH1 register is the high byte of the 16-bit Timer 1.
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C8051F91x-C8051F90x
25.2. Timer 2
Timer 2 is a 16-bit timer formed by two 8-bit SFRs: TMR2L (low byte) and TMR2H (high byte). Timer 2 may operate in 16-bit auto-reload mode or (split) 8-bit auto-reload mode. The T2SPLIT bit (TMR2CN.3) defines the Timer 2 operation mode. Timer 2 can also be used in Capture Mode to measure the SmaRTClock or the Comparator 0 period with respect to another oscillator. The ability to measure the Comparator 0 period with respect to the system clock is makes using Touch Sense Switches very easy. Timer 2 may be clocked by the system clock, the system clock divided by 12, SmaRTClock divided by 8, or Comparator 0 output. Note that the SmaRTClock divided by 8 and Comparator 0 output is synchronized with the system clock.
25.2.1. 16-bit Timer with Auto-Reload
When T2SPLIT (TMR2CN.3) is zero, Timer 2 operates as a 16-bit timer with auto-reload. Timer 2 can be clocked by SYSCLK, SYSCLK divided by 12, SmaRTClock divided by 8, or Comparator 0 output. As the 16-bit timer register increments and overflows from 0xFFFF to 0x0000, the 16-bit value in the Timer 2 reload registers (TMR2RLH and TMR2RLL) is loaded into the Timer 2 register as shown in Figure 25.4, and the Timer 2 High Byte Overflow Flag (TMR2CN.7) is set. If Timer 2 interrupts are enabled (if IE.5 is set), an interrupt will be generated on each Timer 2 overflow. Additionally, if Timer 2 interrupts are enabled and the TF2LEN bit is set (TMR2CN.5), an interrupt will be generated each time the lower 8 bits (TMR2L) overflow from 0xFF to 0x00.
CKCON T2XCLK[1:0]
TTTTTTSS 3 3 2 2 1 0 CC MMMMMM A A HLHL 10
To SMBus To ADC, SMBus
SYSCLK / 12
00
TL2 Overflow TR2 TCLK
SmaRTClock / 8 Comparator 0
01 11
0
TMR2L
TMR2H TMR2CN
1 SYSCLK TMR2RLL TMR2RLH
Reload
TF2H TF2L TF2LEN TF2CEN T2SPLIT TR2 T2XCLK
Interrupt
Figure 25.4. Timer 2 16-Bit Mode Block Diagram
280
Rev. 1.0
C8051F91x-C8051F90x
25.2.2. 8-bit Timers with Auto-Reload
When T2SPLIT is set, Timer 2 operates as two 8-bit timers (TMR2H and TMR2L). Both 8-bit timers operate in auto-reload mode as shown in Figure 25.5. TMR2RLL holds the reload value for TMR2L; TMR2RLH holds the reload value for TMR2H. The TR2 bit in TMR2CN handles the run control for TMR2H. TMR2L is always running when configured for 8-bit Mode. Each 8-bit timer may be configured to use SYSCLK, SYSCLK divided by 12, SmaRTClock divided by 8 or Comparator 0 output. The Timer 2 Clock Select bits (T2MH and T2ML in CKCON) select either SYSCLK or the clock defined by the Timer 2 External Clock Select bits (T2XCLK[1:0] in TMR2CN), as follows: T2MH 0 0 0 0 1 T2XCLK[1:0] 00 01 10 11 X TMR2H Clock Source SYSCLK / 12 SmaRTClock / 8 Reserved Comparator 0 SYSCLK T2ML 0 0 0 0 1 T2XCLK[1:0] 00 01 10 11 X TMR2L Clock Source SYSCLK / 12 SmaRTClock / 8 Reserved Comparator 0 SYSCLK
The TF2H bit is set when TMR2H overflows from 0xFF to 0x00; the TF2L bit is set when TMR2L overflows from 0xFF to 0x00. When Timer 2 interrupts are enabled (IE.5), an interrupt is generated each time TMR2H overflows. If Timer 2 interrupts are enabled and TF2LEN (TMR2CN.5) is set, an interrupt is generated each time either TMR2L or TMR2H overflows. When TF2LEN is enabled, software must check the TF2H and TF2L flags to determine the source of the Timer 2 interrupt. The TF2H and TF2L interrupt flags are not cleared by hardware and must be manually cleared by software.
CKCON T2XCLK[1:0]
TTTTTTSS 3 3 2 2 1 0 CC MMMMMM A A HLHL 10
TMR2RLH
Reload
To SMBus
SYSCLK / 12
00 0
SmaRTClock / 8 Comparator 0
01 TR2 11 1
TCLK
TMR2H TMR2CN
TMR2RLL SYSCLK
Reload
TF2H TF2L TF2LEN TF2CEN T2SPLIT TR2 T2XCLK
Interrupt
1 TCLK 0 TMR2L To ADC, SMBus
Figure 25.5. Timer 2 8-Bit Mode Block Diagram
Rev. 1.0
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C8051F91x-C8051F90x
25.2.3. Comparator 0/SmaRTClock Capture Mode
The Capture Mode in Timer 2 allows either Comparator 0 or the SmaRTClock period to be measured against the system clock or the system clock divided by 12. Comparator 0 and the SmaRTClock period can also be compared against each other. Timer 2 Capture Mode is enabled by setting TF2CEN to 1. Timer 2 should be in 16-bit auto-reload mode when using Capture Mode. When Capture Mode is enabled, a capture event will be generated either every Comparator 0 rising edge or every 8 SmaRTClock clock cycles, depending on the T2XCLK1 setting. When the capture event occurs, the contents of Timer 2 (TMR2H:TMR2L) are loaded into the Timer 2 reload registers (TMR2RLH:TMR2RLL) and the TF2H flag is set (triggering an interrupt if Timer 2 interrupts are enabled). By recording the difference between two successive timer capture values, the Comparator 0 or SmaRTClock period can be determined with respect to the Timer 2 clock. The Timer 2 clock should be much faster than the capture clock to achieve an accurate reading. For example, if T2ML = 1b, T2XCLK1 = 0b, and TF2CEN = 1b, Timer 2 will clock every SYSCLK and capture every SmaRTClock clock divided by 8. If the SYSCLK is 24.5 MHz and the difference between two successive captures is 5984, then the SmaRTClock clock is as follows: 24.5 MHz/(5984/8) = 0.032754 MHz or 32.754 kHz. This mode allows software to determine the exact SmaRTClock frequency in self-oscillate mode and the time between consecutive Comparator 0 rising edges, which is useful for detecting changes in the capacitance of a Touch Sense Switch.
T2XCLK[1:0] CKCON
TTTTTTSS 3 3 2 2 1 0CC MMMMMM A A HLHL 10
SYSCLK / 12
X0
Comparator 0 SmaRTClock / 8
01 11 0
TR2 TCLK
TMR2L
TMR2H
SYSCLK
1
Capture
T2XCLK1
TF2CEN
TMR2RLL TMR2RLH TMR2CN
SmaRTClock / 8
0
TF2H TF2L TF2LEN TF2CEN T2SPLIT TR2 T2XCLK1 T2XCLK0
Interrupt
Comparator 0
1
Figure 25.6. Timer 2 Capture Mode Block Diagram
282
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SFR Definition 25.8. TMR2CN: Timer 2 Control
Bit Name Type Reset 7 TF2H R/W 0 6 TF2L R/W 0 5 TF2LEN R/W 0 4 TF2CEN R/W 0 3 T2SPLIT R/W 0 2 TR2 R/W 0 0 1 0
T2XCLK[1:0] R/W 0
SFR Page = 0x0; SFR Address = 0xC8; Bit-Addressable Bit Name 7 TF2H Timer 2 High Byte Overflow Flag.
Function
Set by hardware when the Timer 2 high byte overflows from 0xFF to 0x00. In 16 bit mode, this will occur when Timer 2 overflows from 0xFFFF to 0x0000. When the Timer 2 interrupt is enabled, setting this bit causes the CPU to vector to the Timer 2 interrupt service routine. This bit is not automatically cleared by hardware. 6 TF2L Timer 2 Low Byte Overflow Flag. Set by hardware when the Timer 2 low byte overflows from 0xFF to 0x00. TF2L will be set when the low byte overflows regardless of the Timer 2 mode. This bit is not automatically cleared by hardware. 5 TF2LEN Timer 2 Low Byte Interrupt Enable. When set to 1, this bit enables Timer 2 Low Byte interrupts. If Timer 2 interrupts are also enabled, an interrupt will be generated when the low byte of Timer 2 overflows. 4 3 TF2CEN T2SPLIT Timer 2 Capture Enable. When set to 1, this bit enables Timer 2 Capture Mode. Timer 2 Split Mode Enable. When set to 1, Timer 2 operates as two 8-bit timers with auto-reload. Otherwise, Timer 2 operates in 16-bit auto-reload mode. 2 TR2 Timer 2 Run Control. Timer 2 is enabled by setting this bit to 1. In 8-bit mode, this bit enables/disables TMR2H only; TMR2L is always enabled in split mode. 1:0 T2XCLK[1:0] Timer 2 External Clock Select. This bit selects the "external" and "capture trigger" clock sources for Timer 2. If Timer 2 is in 8-bit mode, this bit selects the "external" clock source for both timer bytes. Timer 2 Clock Select bits (T2MH and T2ML in register CKCON) may still be used to select between the "external" clock and the system clock for either timer. Note: External clock sources are synchronized with the system clock. 00: External Clock is SYSCLK/12. Capture trigger is SmaRTClock/8. 01: External Clock is Comparator 0. Capture trigger is SmaRTClock/8. 10: External Clock is SYSCLK/12. Capture trigger is Comparator 0. 11: External Clock is SmaRTClock/8. Capture trigger is Comparator 0.
Rev. 1.0
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C8051F91x-C8051F90x
SFR Definition 25.9. TMR2RLL: Timer 2 Reload Register Low Byte
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
TMR2RLL[7:0] R/W 0 0 0 0
SFR Page = 0x0; SFR Address = 0xCA Bit Name 7:0
Function
TMR2RLL[7:0] Timer 2 Reload Register Low Byte. TMR2RLL holds the low byte of the reload value for Timer 2.
SFR Definition 25.10. TMR2RLH: Timer 2 Reload Register High Byte
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
TMR2RLH[7:0] R/W 0 0 0 0
SFR Page = 0x0; SFR Address = 0xCB Bit Name
Function
7:0 TMR2RLH[7:0] Timer 2 Reload Register High Byte. TMR2RLH holds the high byte of the reload value for Timer 2.
284
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SFR Definition 25.11. TMR2L: Timer 2 Low Byte
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
TMR2L[7:0] R/W 0 0 0 0
SFR Page = 0x0; SFR Address = 0xCC Bit Name 7:0 TMR2L[7:0] Timer 2 Low Byte.
Function
In 16-bit mode, the TMR2L register contains the low byte of the 16-bit Timer 2. In 8bit mode, TMR2L contains the 8-bit low byte timer value.
SFR Definition 25.12. TMR2H Timer 2 High Byte
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
TMR2H[7:0] R/W 0 0 0 0
SFR Page = 0x0; SFR Address = 0xCD Bit Name 7:0 TMR2H[7:0] Timer 2 Low Byte.
Function
In 16-bit mode, the TMR2H register contains the high byte of the 16-bit Timer 2. In 8bit mode, TMR2H contains the 8-bit high byte timer value.
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C8051F91x-C8051F90x
25.3. Timer 3
Timer 3 is a 16-bit timer formed by two 8-bit SFRs: TMR3L (low byte) and TMR3H (high byte). Timer 3 may operate in 16-bit auto-reload mode or (split) 8-bit auto-reload mode. The T3SPLIT bit (TMR2CN.3) defines the Timer 3 operation mode. Timer 3 can also be used in Capture Mode to measure the external oscillator source or the Comparator 1 period with respect to another oscillator. The ability to measure the Comparator 1 period with respect to the system clock is makes using Touch Sense Switches very easy. Timer 3 may be clocked by the system clock, the system clock divided by 12, external oscillator source divided by 8, or Comparator 1 output. The external oscillator source divided by 8 and Comparator 1 output is synchronized with the system clock.
25.3.1. 16-bit Timer with Auto-Reload
When T3SPLIT (TMR3CN.3) is zero, Timer 3 operates as a 16-bit timer with auto-reload. Timer 3 can be clocked by SYSCLK, SYSCLK divided by 12, external oscillator clock source divided by 8, or Comparator 1 output. As the 16-bit timer register increments and overflows from 0xFFFF to 0x0000, the 16-bit value in the Timer 3 reload registers (TMR3RLH and TMR3RLL) is loaded into the Timer 3 register as shown in Figure 25.7, and the Timer 3 High Byte Overflow Flag (TMR3CN.7) is set. If Timer 3 interrupts are enabled (if EIE1.7 is set), an interrupt will be generated on each Timer 3 overflow. Additionally, if Timer 3 interrupts are enabled and the TF3LEN bit is set (TMR3CN.5), an interrupt will be generated each time the lower 8 bits (TMR3L) overflow from 0xFF to 0x00.
CKCON T3XCLK[1:0]
TTTTTTSS 3 3 2 2 1 0 CC MMMMMM A A HLHL 10
SYSCLK / 12 External Clock / 8 Comparator 1
00
To ADC
01 11
0
TR3 TCLK
TMR3L
TMR3H TMR3CN
1 SYSCLK TMR3RLL TMR3RLH
Reload
TF3H TF3L TF3LEN TF3CEN T3SPLIT TR3 T3XCLK1 T3XCLK0
Interrupt
Figure 25.7. Timer 3 16-Bit Mode Block Diagram
286
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C8051F91x-C8051F90x
25.3.2. 8-bit Timers with Auto-Reload
When T3SPLIT is set, Timer 3 operates as two 8-bit timers (TMR3H and TMR3L). Both 8-bit timers operate in auto-reload mode as shown in Figure 25.8. TMR3RLL holds the reload value for TMR3L; TMR3RLH holds the reload value for TMR3H. The TR3 bit in TMR3CN handles the run control for TMR3H. TMR3L is always running when configured for 8-bit Mode. Each 8-bit timer may be configured to use SYSCLK, SYSCLK divided by 12, the external oscillator clock source divided by 8, or Comparator 1. The Timer 3 Clock Select bits (T3MH and T3ML in CKCON) select either SYSCLK or the clock defined by the Timer 3 External Clock Select bits (T3XCLK[1:0] in TMR3CN), as follows: T3MH 0 0 0 0 1 T3XCLK[1:0] 00 01 10 11 X TMR3H Clock Source SYSCLK / 12 Comparator 1 Reserved External Clock / 8 SYSCLK T3ML 0 0 0 0 1 T3XCLK[1:0] 00 01 10 11 X TMR3L Clock Source SYSCLK / 12 Comparator 1 Reserved External Clock / 8 SYSCLK
The TF3H bit is set when TMR3H overflows from 0xFF to 0x00; the TF3L bit is set when TMR3L overflows from 0xFF to 0x00. When Timer 3 interrupts are enabled, an interrupt is generated each time TMR3H overflows. If Timer 3 interrupts are enabled and TF3LEN (TMR3CN.5) is set, an interrupt is generated each time either TMR3L or TMR3H overflows. When TF3LEN is enabled, software must check the TF3H and TF3L flags to determine the source of the Timer 3 interrupt. The TF3H and TF3L interrupt flags are not cleared by hardware and must be manually cleared by software.
CKCON T3XCLK[1:0]
TTTTTTSS 3 3 2 2 1 0CC MMMMMM A A HLHL 10
TMR3RLH
Reload
SYSCLK / 12 Comparator 1 External Clock / 8
00 0 01 TR3 11 1 Reload TMR3CN TCLK TMR3H
TF3H TF3L TF3LEN TF3CEN T3SPLIT TR3 T3XCLK1 T3XCLK0
Interrupt
TMR3RLL SYSCLK
1 TCLK 0 TMR3L To ADC
Figure 25.8. Timer 3 8-Bit Mode Block Diagram.
Rev. 1.0
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C8051F91x-C8051F90x
25.3.3. Comparator 1/External Oscillator Capture Mode
The Capture Mode in Timer 3 allows either Comparator 1 or the external oscillator period to be measured against the system clock or the system clock divided by 12. Comparator 1 and the external oscillator period can also be compared against each other. Setting TF3CEN to 1 enables the Comparator 1/External Oscillator Capture Mode for Timer 3. In this mode, T3SPLIT should be set to 0, as the full 16-bit timer is used. When Capture Mode is enabled, a capture event will be generated either every Comparator 1 rising edge or every 8 external clock cycles, depending on the T3XCLK1 setting. When the capture event occurs, the contents of Timer 3 (TMR3H:TMR3L) are loaded into the Timer 3 reload registers (TMR3RLH:TMR3RLL) and the TF3H flag is set (triggering an interrupt if Timer 3 interrupts are enabled). By recording the difference between two successive timer capture values, the Comparator 1 or external clock period can be determined with respect to the Timer 3 clock. The Timer 3 clock should be much faster than the capture clock to achieve an accurate reading. For example, if T3ML = 1b, T3XCLK1 = 0b, and TF3CEN = 1b, Timer 3 will clock every SYSCLK and capture every Comparator 1 rising edge. If SYSCLK is 24.5 MHz and the difference between two successive captures is 350 counts, then the Comparator 1 period is: 350 x (1 / 24.5 MHz) = 14.2 s. This mode allows software to determine the exact frequency of the external oscillator in C and RC mode or the time between consecutive Comparator 0 rising edges, which is useful for detecting changes in the capacitance of a Touch Sense Switch.
T 3X C LK [1:0] CKCON
T 3 M H T 3 M L T 2 M H TTTSS 2 1 0CC MMMA A 10 L
S Y S C LK / 1 2
X0
E xternal C lock / 8 C om parato r 1
01 11 0
TR3 T C LK
TM R3L
T M R 3H
S Y S C LK
1
C apture
T 3X C LK 1
TF3CEN
T M R 3R L L
T M R 3 R LH TMR3CN
C om p arator 1
0
T F 3H T F 3L TF3LEN T F 3C E N T 3S P LIT TR3 T3XCLK1 T3XCLK0
Inte rrupt
E xtern al C lock / 8
1
Figure 25.9. Timer 3 Capture Mode Block Diagram
288
Rev. 1.0
C8051F91x-C8051F90x
SFR Definition 25.13. TMR3CN: Timer 3 Control
Bit Name Type Reset 7 TF3H R/W 0 6 TF3L R/W 0 5 TF3LEN R/W 0 4 TF3CEN R/W 0 3 T3SPLIT R/W 0 2 TR3 R/W 0 0 1 0
T3XCLK[1:0] R/W 0
SFR Page = 0x0; SFR Address = 0x91 Bit Name 7 TF3H Timer 3 High Byte Overflow Flag.
Function
Set by hardware when the Timer 3 high byte overflows from 0xFF to 0x00. In 16 bit mode, this will occur when Timer 3 overflows from 0xFFFF to 0x0000. When the Timer 3 interrupt is enabled, setting this bit causes the CPU to vector to the Timer 3 interrupt service routine. This bit is not automatically cleared by hardware. 6 TF3L Timer 3 Low Byte Overflow Flag. Set by hardware when the Timer 3 low byte overflows from 0xFF to 0x00. TF3L will be set when the low byte overflows regardless of the Timer 3 mode. This bit is not automatically cleared by hardware. 5 TF3LEN Timer 3 Low Byte Interrupt Enable. When set to 1, this bit enables Timer 3 Low Byte interrupts. If Timer 3 interrupts are also enabled, an interrupt will be generated when the low byte of Timer 3 overflows. 4 3 TF3CEN T3SPLIT Timer 3 Comparator 1/External Oscillator Capture Enable. When set to 1, this bit enables Timer 3 Capture Mode. Timer 3 Split Mode Enable. When this bit is set, Timer 3 operates as two 8-bit timers with auto-reload. 0: Timer 3 operates in 16-bit auto-reload mode. 1: Timer 3 operates as two 8-bit auto-reload timers. 2 TR3 Timer 3 Run Control. Timer 3 is enabled by setting this bit to 1. In 8-bit mode, this bit enables/disables TMR3H only; TMR3L is always enabled in split mode. 1:0 T3XCLK[1:0] Timer 3 External Clock Select. This bit selects the "external" and "capture trigger" clock sources for Timer 3. If Timer 3 is in 8-bit mode, this bit selects the "external" clock source for both timer bytes. Timer 3 Clock Select bits (T3MH and T3ML in register CKCON) may still be used to select between the "external" clock and the system clock for either timer. Note: External clock sources are synchronized with the system clock. 00: External Clock is SYSCLK /12. Capture trigger is Comparator 1. 01: External Clock is External Oscillator/8. Capture trigger is Comparator 1. 10: External Clock is SYSCLK/12. Capture trigger is External Oscillator/8. 11: External Clock is Comparator 1. Capture trigger is External Oscillator/8.
Rev. 1.0
289
C8051F91x-C8051F90x
SFR Definition 25.14. TMR3RLL: Timer 3 Reload Register Low Byte
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
TMR3RLL[7:0] R/W 0 0 0 0
SFR Page = 0x0; SFR Address = 0x92 Bit Name 7:0
Function
TMR3RLL[7:0] Timer 3 Reload Register Low Byte. TMR3RLL holds the low byte of the reload value for Timer 3.
SFR Definition 25.15. TMR3RLH: Timer 3 Reload Register High Byte
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
TMR3RLH[7:0] R/W 0 0 0 0
SFR Page = 0x0; SFR Address = 0x93 Bit Name
Function
7:0 TMR3RLH[7:0] Timer 3 Reload Register High Byte. TMR3RLH holds the high byte of the reload value for Timer 3.
290
Rev. 1.0
C8051F91x-C8051F90x
SFR Definition 25.16. TMR3L: Timer 3 Low Byte
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
TMR3L[7:0] R/W 0 0 0 0
SFR Page = 0x0; SFR Address = 0x94 Bit Name 7:0 TMR3L[7:0] Timer 3 Low Byte.
Function
In 16-bit mode, the TMR3L register contains the low byte of the 16-bit Timer 3. In 8-bit mode, TMR3L contains the 8-bit low byte timer value.
SFR Definition 25.17. TMR3H Timer 3 High Byte
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
TMR3H[7:0] R/W 0 0 0 0
SFR Page = 0x0; SFR Address = 0x95 Bit Name 7:0 TMR3H[7:0] Timer 3 High Byte.
Function
In 16-bit mode, the TMR3H register contains the high byte of the 16-bit Timer 3. In 8-bit mode, TMR3H contains the 8-bit high byte timer value.
Rev. 1.0
291
C8051F91x-C8051F90x
26. Programmable Counter Array
The Programmable Counter Array (PCA0) provides enhanced timer functionality while requiring less CPU intervention than the standard 8051 counter/timers. The PCA consists of a dedicated 16-bit counter/timer and six 16-bit capture/compare modules. Each capture/compare module has its own associated I/O line (CEXn) which is routed through the Crossbar to Port I/O when enabled. The counter/timer is driven by a programmable timebase that can select between seven sources: system clock, system clock divided by four, system clock divided by twelve, the external oscillator clock source divided by 8, SmaRTClock divided by 8 ('F912 and 'F902 devices only), Timer 0 overflows, or an external clock signal on the ECI input pin. Each capture/compare module may be configured to operate independently in one of six modes: EdgeTriggered Capture, Software Timer, High-Speed Output, Frequency Output, 8 to 11-Bit PWM, or 16-Bit PWM (each mode is described in Section "26.3. Capture/Compare Modules" on page 296). The external oscillator clock option is ideal for real-time clock (RTC) functionality, allowing the PCA to be clocked by a precision external oscillator while the internal oscillator drives the system clock. The PCA is configured and controlled through the system controller's Special Function Registers. The PCA block diagram is shown in Figure 26.1. Important Note: The PCA Module 5 may be used as a watchdog timer (WDT), and is enabled in this mode following a system reset. Access to certain PCA registers is restricted while WDT mode is enabled. See Section 26.4 for details.
SYSCLK/12 SYSCLK/4 Timer 0 Overflow ECI SYSCLK External Clock/8 SmaRTClock/8* *Only available on `F912 and `F902 devices. PCA CLOCK MUX 16-Bit Counter/Timer
Capture/Compare Module 0
Capture/Compare Module 1
Capture/Compare Module 2
Capture/Compare Module 3
Capture/Compare Module 4
Capture/Compare Module 5 / WDT
CEX0
CEX1
CEX2
CEX3
CEX4
CEX5
ECI
Crossbar
Port I/O
Figure 26.1. PCA Block Diagram
292
Rev. 1.0
C8051F91x-C8051F90x
26.1. PCA Counter/Timer
The 16-bit PCA counter/timer consists of two 8-bit SFRs: PCA0L and PCA0H. PCA0H is the high byte (MSB) of the 16-bit counter/timer and PCA0L is the low byte (LSB). Reading PCA0L automatically latches the value of PCA0H into a "snapshot" register; the following PCA0H read accesses this "snapshot" register. Reading the PCA0L Register first guarantees an accurate reading of the entire 16-bit PCA0 counter. Reading PCA0H or PCA0L does not disturb the counter operation. The CPS2-CPS0 bits in the PCA0MD register select the timebase for the counter/timer as shown in Table 26.1. When the counter/timer overflows from 0xFFFF to 0x0000, the Counter Overflow Flag (CF) in PCA0MD is set to logic 1 and an interrupt request is generated if CF interrupts are enabled. Setting the ECF bit in PCA0MD to logic 1 enables the CF flag to generate an interrupt request. The CF bit is not automatically cleared by hardware when the CPU vectors to the interrupt service routine, and must be cleared by software. Clearing the CIDL bit in the PCA0MD register allows the PCA to continue normal operation while the CPU is in Idle mode.
Table 26.1. PCA Timebase Input Options
CPS2 0 0 0 0 1 1 1 1 CPS1 0 0 1 1 0 0 1 1 CPS0 0 1 0 1 0 1 0 1 Timebase System clock divided by 12 System clock divided by 4 Timer 0 overflow High-to-low transitions on ECI (max rate = system clock divided by 4) System clock External oscillator source divided by 81 SmaRTClock oscillator source divided by 82 Reserved
Notes: 1. External oscillator source divided by 8 is synchronized with the system clock. 2. SmaRTClock oscillator source divided by 8 is synchronized with the system clock and is only available on 'F912 and 'F902 devices. This setting is reserved on all other devices.
Rev. 1.0
293
C8051F91x-C8051F90x
IDLE
PCA0MD
CWW I DD DT L LEC K CCCE PPPC SSSF 210
PCA0CN
CCCCCCCC FRCCCCCC FFFFFF 543210
PCA0L read
To SFR Bus
Snapshot Register
SYSCLK/12 SYSCLK/4 Timer 0 Overflow ECI SYSCLK External Clock/8 SmaRTClock/8* 000 001 010 011 100 101 110 To PCA Modules 0 1
PCA0H
PCA0L
Overflow CF
To PCA Interrupt System
*Only available on `F912 and `F902 devices.
Figure 26.2. PCA Counter/Timer Block Diagram
26.2. PCA0 Interrupt Sources
Figure 26.3 shows a diagram of the PCA interrupt tree. There are eight independent event flags that can be used to generate a PCA0 interrupt. They are: the main PCA counter overflow flag (CF), which is set upon a 16-bit overflow of the PCA0 counter, an intermediate overflow flag (COVF), which can be set on an overflow from the 8th, 9th, 10th, or 11th bit of the PCA0 counter, and the individual flags for each PCA channel (CCF0, CCF1, CCF2, CCF3, CCF4, and CCF5), which are set according to the operation mode of that module. These event flags are always set when the trigger condition occurs. Each of these flags can be individually selected to generate a PCA0 interrupt, using the corresponding interrupt enable flag (ECF for CF, ECOV for COVF, and ECCFn for each CCFn). PCA0 interrupts must be globally enabled before any individual interrupt sources are recognized by the processor. PCA0 interrupts are globally enabled by setting the EA bit and the EPCA0 bit to logic 1.
294
Rev. 1.0
C8051F91x-C8051F90x
(for n = 0 to 5)
PCA0CPMn
P ECCMT P E WC A A AOWC MOPP TGMC 1 MP N n n n F 6nnn n n PCA Counter/Timer 8, 9, 10 or 11-bit Overflow PCA Counter/Timer 16bit Overflow
PCA0CN
CCCCCCCC FRCCCCCC FFFFFF 543210
PCA0MD
C WW I DD DTL LEC K CCCE PPPC SSSF 210
PCA0PWM
ACE ROC S VO EFV L C L S E L 1 C L S E L 0 Set 8, 9, 10, or 11 bit Operation
0 1 0 1
ECCF0
EPCA0
0 1
EA
0 1
PCA Module 0 (CCF0)
ECCF1
0 1
Interrupt Priority Decoder
PCA Module 1 (CCF1)
ECCF2
0 1
PCA Module 2 (CCF2)
ECCF3
0 1
PCA Module 3 (CCF3)
ECCF4
0 1
PCA Module 4 (CCF4)
ECCF5
0 1
PCA Module 5 (CCF5)
0 1
Figure 26.3. PCA Interrupt Block Diagram
Rev. 1.0
295
C8051F91x-C8051F90x
26.3. Capture/Compare Modules
Each module can be configured to operate independently in one of six operation modes: edge-triggered capture, software timer, high speed output, frequency output, 8 to 11-bit pulse width modulator, or 16-bit pulse width modulator. Each module has special function registers (SFRs) associated with it in the CIP-51 system controller. These registers are used to exchange data with a module and configure the module's mode of operation. Table 26.2 summarizes the bit settings in the PCA0CPMn and PCA0PWM registers used to select the PCA capture/compare module's operating mode. Note that all modules set to use 8, 9, 10, or 11-bit PWM mode must use the same cycle length (8-11 bits). Setting the ECCFn bit in a PCA0CPMn register enables the module's CCFn interrupt.
Table 26.2. PCA0CPM and PCA0PWM Bit Settings for PCA Capture/Compare Modules
Operational Mode Bit Number Capture triggered by positive edge on CEXn Capture triggered by negative edge on CEXn Capture triggered by any transition on CEXn Software Timer High-Speed Output Frequency Output 8-Bit Pulse Width Modulator (Note 7) 9-Bit Pulse Width Modulator (Note 7) 10-Bit Pulse Width Modulator (Note 7) 11-Bit Pulse Width Modulator (Note 7) 16-Bit Pulse Width Modulator 7 X X X X X X 0 0 0 0 1 6 X X X C C C C C C C C PCA0CPMn 5432 1000 0100 1100 0010 0011 0001 00E0 00E0 00E0 00E0 00E0 1 0 0 0 0 0 1 1 1 1 1 1 0 A A A A A A A A A A A 7 0 0 0 0 0 0 0 D D D 0 PCA0PWM 6 5 4-2 1-0 X B XXX XX X B XXX XX X B XXX XX X B XXX XX X B XXX XX X B XXX XX X B XXX 00 X B XXX 01 X B XXX 10 X B XXX 11 X B XXX XX
Notes: 1. X = Don't Care (no functional difference for individual module if 1 or 0). 2. A = Enable interrupts for this module (PCA interrupt triggered on CCFn set to 1). 3. B = Enable 8th, 9th, 10th or 11th bit overflow interrupt (Depends on setting of CLSEL[1:0]). 4. C = When set to 0, the digital comparator is off. For high speed and frequency output modes, the associated pin will not toggle. In any of the PWM modes, this generates a 0% duty cycle (output = 0). 5. D = Selects whether the Capture/Compare register (0) or the Auto-Reload register (1) for the associated channel is accessed via addresses PCA0CPHn and PCA0CPLn. 6. E = When set, a match event will cause the CCFn flag for the associated channel to be set. 7. All modules set to 8, 9, 10 or 11-bit PWM mode use the same cycle length setting.
296
Rev. 1.0
C8051F91x-C8051F90x
26.3.1. Edge-triggered Capture Mode
In this mode, a valid transition on the CEXn pin causes the PCA to capture the value of the PCA counter/timer and load it into the corresponding module's 16-bit capture/compare register (PCA0CPLn and PCA0CPHn). The CAPPn and CAPNn bits in the PCA0CPMn register are used to select the type of transition that triggers the capture: low-to-high transition (positive edge), high-to-low transition (negative edge), or either transition (positive or negative edge). When a capture occurs, the Capture/Compare Flag (CCFn) in PCA0CN is set to logic 1. An interrupt request is generated if the CCFn interrupt for that module is enabled. The CCFn bit is not automatically cleared by hardware when the CPU vectors to the interrupt service routine, and must be cleared by software. If both CAPPn and CAPNn bits are set to logic 1, then the state of the Port pin associated with CEXn can be read directly to determine whether a rising-edge or falling-edge caused the capture.
PCA Interrupt
PCA0CPMn
P ECCMT P E WC A A AOWC MOPP TGMC 1 MP N n n n F 6nnn n n
xx 000x
PCA0CN
CC FR CCC CCC FFF 210
(to CCFn)
PCA0CPLn
PCA0CPHn
0
Port I/O
Crossbar
CEXn
1 0 1 PCA Timebase
Capture
PCA0L
PCA0H
Figure 26.4. PCA Capture Mode Diagram
Note: The CEXn input signal must remain high or low for at least 2 system clock cycles to be recognized by the hardware.
Rev. 1.0
297
C8051F91x-C8051F90x
26.3.2. Software Timer (Compare) Mode
In Software Timer mode, the PCA counter/timer value is compared to the module's 16-bit capture/compare register (PCA0CPHn and PCA0CPLn). When a match occurs, the Capture/Compare Flag (CCFn) in PCA0CN is set to logic 1. An interrupt request is generated if the CCFn interrupt for that module is enabled. The CCFn bit is not automatically cleared by hardware when the CPU vectors to the interrupt service routine, and must be cleared by software. Setting the ECOMn and MATn bits in the PCA0CPMn register enables Software Timer mode. Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/Compare registers, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit to 0; writing to PCA0CPHn sets ECOMn to 1.
Write to PCA0CPLn Reset Write to PCA0CPHn 0
ENB
ENB
PCA Interrupt
1
PCA0CPMn
P ECCMT P E WC A A AOWC MOPP TGMC 1 MP N n n n F 6nnn n n
x 00 00x Enable Match 0 1
PCA0CN PCA0CPLn PCA0CPHn
CC FR CCC CCC FFF 210
16-bit Comparator
PCA Timebase
PCA0L
PCA0H
Figure 26.5. PCA Software Timer Mode Diagram
298
Rev. 1.0
C8051F91x-C8051F90x
26.3.3. High-Speed Output Mode
In High-speed output mode, a module's associated CEXn pin is toggled each time a match occurs between the PCA Counter and the module's 16-bit capture/compare register (PCA0CPHn and PCA0CPLn). When a match occurs, the Capture/Compare Flag (CCFn) in PCA0CN is set to logic 1. An interrupt request is generated if the CCFn interrupt for that module is enabled. The CCFn bit is not automatically cleared by hardware when the CPU vectors to the interrupt service routine, and must be cleared by software. Setting the TOGn, MATn, and ECOMn bits in the PCA0CPMn register enables the High-Speed Output mode. If ECOMn is cleared, the associated pin will retain its state, and not toggle on the next match event. Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/Compare registers, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit to 0; writing to PCA0CPHn sets ECOMn to 1.
Write to PCA0CPLn Reset Write to PCA0CPHn 0
ENB
PCA0CPMn
ENB
1
P ECCMT P E WC A A AOWC MOPP TGMC 1 MPN n n n F 6nnn n n
x 00 0x PCA Interrupt
PCA0CN PCA0CPLn PCA0CPHn
CC FR CCC CCC FFF 210
Enable
16-bit Comparator
Match
0 1
TOGn
Toggle
0 CEXn 1
Crossbar
Port I/O
PCA Timebase
PCA0L
PCA0H
Figure 26.6. PCA High-Speed Output Mode Diagram
Rev. 1.0
299
C8051F91x-C8051F90x
26.3.4. Frequency Output Mode
Frequency Output Mode produces a programmable-frequency square wave on the module's associated CEXn pin. The capture/compare module high byte holds the number of PCA clocks to count before the output is toggled. The frequency of the square wave is then defined by Equation 26.1.
F PCA F CEXn = ---------------------------------------2 PCA0CPHn
Note: A value of 0x00 in the PCA0CPHn register is equal to 256 for this equation.
Equation 26.1. Square Wave Frequency Output
Where FPCA is the frequency of the clock selected by the CPS2-0 bits in the PCA mode register, PCA0MD. The lower byte of the capture/compare module is compared to the PCA counter low byte; on a match, CEXn is toggled and the offset held in the high byte is added to the matched value in PCA0CPLn. Frequency Output Mode is enabled by setting the ECOMn, TOGn, and PWMn bits in the PCA0CPMn register. Note that the MATn bit should normally be set to 0 in this mode. If the MATn bit is set to 1, the CCFn flag for the channel will be set when the 16-bit PCA0 counter and the 16-bit capture/compare register for the channel are equal.
Write to PCA0CPLn Reset Write to PCA0CPHn 0
ENB
PCA0CPMn
ENB
1
P ECCMT P E WC A A AOWC MOPP TGMC 1 MP N n n n F 6nnn n n
x 000 x Enable
PCA0CPLn
8-bit Adder
Adder Enable
PCA0CPHn
TOGn
Toggle 8-bit Comparator
match
0 CEXn 1
Crossbar
Port I/O
PCA Timebase
PCA0L
Figure 26.7. PCA Frequency Output Mode
300
Rev. 1.0
C8051F91x-C8051F90x
26.3.5. 8-Bit, 9-Bit, 10-Bit and 11-Bit Pulse Width Modulator Modes
Each module can be used independently to generate a pulse width modulated (PWM) output on its associated CEXn pin. The frequency of the output is dependent on the timebase for the PCA counter/timer, and the setting of the PWM cycle length (8, 9, 10 or 11-bits). For backwards-compatibility with the 8-bit PWM mode available on other devices, the 8-bit PWM mode operates slightly different than 9, 10 and 11bit PWM modes. It is important to note that all channels configured for 8/9/10/11-bit PWM mode will use the same cycle length. It is not possible to configure one channel for 8-bit PWM mode and another for 11-bit mode (for example). However, other PCA channels can be configured to Pin Capture, HighSpeed Output, Software Timer, Frequency Output, or 16-bit PWM mode independently. 26.3.5.1. 8-Bit Pulse Width Modulator Mode The duty cycle of the PWM output signal in 8-bit PWM mode is varied using the module's PCA0CPLn capture/compare register. When the value in the low byte of the PCA counter/timer (PCA0L) is equal to the value in PCA0CPLn, the output on the CEXn pin will be set. When the count value in PCA0L overflows, the CEXn output will be reset (see Figure 26.8). Also, when the counter/timer low byte (PCA0L) overflows from 0xFF to 0x00, PCA0CPLn is reloaded automatically with the value stored in the module's capture/compare high byte (PCA0CPHn) without software intervention. Setting the ECOMn and PWMn bits in the PCA0CPMn register, and setting the CLSEL bits in register PCA0PWM to 00b enables 8-Bit Pulse Width Modulator mode. If the MATn bit is set to 1, the CCFn flag for the module will be set each time an 8-bit comparator match (rising edge) occurs. The COVF flag in PCA0PWM can be used to detect the overflow (falling edge), which will occur every 256 PCA clock cycles. The duty cycle for 8-Bit PWM Mode is given in Equation 26.2. Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/Compare registers, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit to 0; writing to PCA0CPHn sets ECOMn to 1.
Duty Cycle = 256 - PCA0CPHn -------------------------------------------------256
Equation 26.2. 8-Bit PWM Duty Cycle
Using Equation 26.2, the largest duty cycle is 100% (PCA0CPHn = 0), and the smallest duty cycle is 0.39% (PCA0CPHn = 0xFF). A 0% duty cycle may be generated by clearing the ECOMn bit to 0.
Write to PCA0CPLn Reset Write to PCA0CPHn 0
ENB
PCA0CPHn
ENB
1
COVF
PCA0PWM
A R S E L EC CO OV VF C L S E L 1 C L S E L 0
PCA0CPMn
P ECCMT P E WC A A AOWC MOPP TGMC 1 MP N n n n F 6nnn n n
0 00x0 x Enable
PCA0CPLn
0x
00
8-bit Comparator
match
S
SET
Q
CEXn
Crossbar
Port I/O
R
PCA Timebase
CLR
Q
PCA0L
Overflow
Figure 26.8. PCA 8-Bit PWM Mode Diagram
Rev. 1.0
301
C8051F91x-C8051F90x
26.3.5.2. 9/10/11-bit Pulse Width Modulator Mode The duty cycle of the PWM output signal in 9/10/11-bit PWM mode should be varied by writing to an "AutoReload" Register, which is dual-mapped into the PCA0CPHn and PCA0CPLn register locations. The data written to define the duty cycle should be right-justified in the registers. The auto-reload registers are accessed (read or written) when the bit ARSEL in PCA0PWM is set to 1. The capture/compare registers are accessed when ARSEL is set to 0. When the least-significant N bits of the PCA0 counter match the value in the associated module's capture/compare register (PCA0CPn), the output on CEXn is asserted high. When the counter overflows from the Nth bit, CEXn is asserted low (see Figure 26.9). Upon an overflow from the Nth bit, the COVF flag is set, and the value stored in the module's auto-reload register is loaded into the capture/compare register. The value of N is determined by the CLSEL bits in register PCA0PWM. The 9, 10 or 11-bit PWM mode is selected by setting the ECOMn and PWMn bits in the PCA0CPMn register, and setting the CLSEL bits in register PCA0PWM to the desired cycle length (other than 8-bits). If the MATn bit is set to 1, the CCFn flag for the module will be set each time a comparator match (rising edge) occurs. The COVF flag in PCA0PWM can be used to detect the overflow (falling edge), which will occur every 512 (9-bit), 1024 (10-bit) or 2048 (11-bit) PCA clock cycles. The duty cycle for 9/10/11-Bit PWM Mode is given in Equation 26.2, where N is the number of bits in the PWM cycle. Important Note About PCA0CPHn and PCA0CPLn Registers: When writing a 16-bit value to the PCA0CPn registers, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit to 0; writing to PCA0CPHn sets ECOMn to 1.
N Duty Cycle = 2 - PCA0CPn ------------------------------------------2N
Equation 26.3. 9, 10, and 11-Bit PWM Duty Cycle
A 0% duty cycle may be generated by clearing the ECOMn bit to 0.
Write to PCA0CPLn Reset Write to PCA0CPHn 0
ENB
R/W when ARSEL = 1
(Auto-Reload)
PCA0CPH:Ln
(right-justified)
PCA0PWM
A R S E L EC CO OV VF C L S E L 1 C L S E L 0
Set "N" bits: 01 = 9 bits 10 = 10 bits 11 = 11 bits
ENB
1
PCA0CPMn
P ECCMT P E WC A A AOWC MOPP TGMC 1 MP N n n n F 6nnn n n
0 00x0 x Enable R/W when ARSEL = 0 x (Capture/Compare)
PCA0CPH:Ln
(right-justified)
N-bit Comparator
match
S
SET
Q
CEXn
Crossbar
Port I/O
R
PCA Timebase
CLR
Q
PCA0H:L
Overflow of Nth Bit
Figure 26.9. PCA 9, 10 and 11-Bit PWM Mode Diagram
302
Rev. 1.0
C8051F91x-C8051F90x
26.3.6. 16-Bit Pulse Width Modulator Mode
A PCA module may also be operated in 16-Bit PWM mode. 16-bit PWM mode is independent of the other (8/9/10/11-bit) PWM modes. In this mode, the 16-bit capture/compare module defines the number of PCA clocks for the low time of the PWM signal. When the PCA counter matches the module contents, the output on CEXn is asserted high; when the 16-bit counter overflows, CEXn is asserted low. To output a varying duty cycle, new value writes should be synchronized with PCA CCFn match interrupts. 16-Bit PWM Mode is enabled by setting the ECOMn, PWMn, and PWM16n bits in the PCA0CPMn register. For a varying duty cycle, match interrupts should be enabled (ECCFn = 1 AND MATn = 1) to help synchronize the capture/compare register writes. If the MATn bit is set to 1, the CCFn flag for the module will be set each time a 16-bit comparator match (rising edge) occurs. The CF flag in PCA0CN can be used to detect the overflow (falling edge). The duty cycle for 16-Bit PWM Mode is given by Equation 26.4. Important Note About Capture/Compare Registers: When writing a 16-bit value to the PCA0 Capture/Compare registers, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit to 0; writing to PCA0CPHn sets ECOMn to 1.
Duty Cycle = 65536 - PCA0CPn ---------------------------------------------------65536
Equation 26.4. 16-Bit PWM Duty Cycle
Using Equation 26.4, the largest duty cycle is 100% (PCA0CPn = 0), and the smallest duty cycle is 0.0015% (PCA0CPn = 0xFFFF). A 0% duty cycle may be generated by clearing the ECOMn bit to 0.
Write to PCA0CPLn Reset Write to PCA0CPHn
0
ENB
ENB
1
PCA0CPMn
PEC WCA MOP 1 MP 6nn n
1
C A P N n
MT P AOW TGM nnn
E C C F n
x Enable
PCA0CPHn
PCA0CPLn
00x0
16-bit Comparator
match
S
SET
Q
CEXn
Crossbar
Port I/O
R
PCA Timebase
CLR
Q
PCA0H
PCA0L
Overflow
Figure 26.10. PCA 16-Bit PWM Mode
Rev. 1.0
303
C8051F91x-C8051F90x
26.4. Watchdog Timer Mode
A programmable watchdog timer (WDT) function is available through the PCA Module 5. The WDT is used to generate a reset if the time between writes to the WDT update register (PCA0CPH2) exceed a specified limit. The WDT can be configured and enabled/disabled as needed by software. With the WDTE bit set in the PCA0MD register, Module 5 operates as a watchdog timer (WDT). The Module 5 high byte is compared to the PCA counter high byte; the Module 5 low byte holds the offset to be used when WDT updates are performed. The Watchdog Timer is enabled on reset. Writes to some PCA registers are restricted while the Watchdog Timer is enabled. The WDT will generate a reset shortly after code begins execution. To avoid this reset, the WDT should be explicitly disabled (and optionally re-configured and re-enabled if it is used in the system).
26.4.1. Watchdog Timer Operation
While the WDT is enabled: * * * * * * PCA counter is forced on. Writes to PCA0L and PCA0H are not allowed. PCA clock source bits (CPS2-CPS0) are frozen. PCA Idle control bit (CIDL) is frozen. Module 5 is forced into software timer mode. Writes to the Module 5 mode register (PCA0CPM5) are disabled.
While the WDT is enabled, writes to the CR bit will not change the PCA counter state; the counter will run until the WDT is disabled. The PCA counter run control bit (CR) will read zero if the WDT is enabled but user software has not enabled the PCA counter. If a match occurs between PCA0CPH5 and PCA0H while the WDT is enabled, a reset will be generated. To prevent a WDT reset, the WDT may be updated with a write of any value to PCA0CPH5. Upon a PCA0CPH5 write, PCA0H plus the offset held in PCA0CPL5 is loaded into PCA0CPH5 (See Figure 26.11).
PC A0M D
C I D L W D T E W D L C K C P S 2 C P S 1 CE PC SF 0
PC A0C PH 5
Enable
8-bit C om parator
M atch
R eset
PCA0CPL5
8-bit Adder
Adder Enable
PC A 0H
PCA0L O verflow
W rite to PCA 0C PH 2
Figure 26.11. PCA Module 5 with Watchdog Timer Enabled
304
Rev. 1.0
C8051F91x-C8051F90x
The 8-bit offset held in PCA0CPH5 is compared to the upper byte of the 16-bit PCA counter. This offset value is the number of PCA0L overflows before a reset. Up to 256 PCA clocks may pass before the first PCA0L overflow occurs, depending on the value of the PCA0L when the update is performed. The total offset is then given (in PCA clocks) by Equation 26.5, where PCA0L is the value of the PCA0L register at the time of the update.
Offset = 256 PCA0CPL5 + 256 - PCA0L
Equation 26.5. Watchdog Timer Offset in PCA Clocks
The WDT reset is generated when PCA0L overflows while there is a match between PCA0CPH5 and PCA0H. Software may force a WDT reset by writing a 1 to the CCF5 flag (PCA0CN.5) while the WDT is enabled.
26.4.2. Watchdog Timer Usage
To configure the WDT, perform the following tasks: * * * * * * Disable the WDT by writing a 0 to the WDTE bit. Select the desired PCA clock source (with the CPS2-CPS0 bits). Load PCA0CPL5 with the desired WDT update offset value. Configure the PCA Idle mode (set CIDL if the WDT should be suspended while the CPU is in Idle mode). Enable the WDT by setting the WDTE bit to 1. Reset the WDT timer by writing to PCA0CPH5.
The PCA clock source and Idle mode select cannot be changed while the WDT is enabled. The watchdog timer is enabled by setting the WDTE or WDLCK bits in the PCA0MD register. When WDLCK is set, the WDT cannot be disabled until the next system reset. If WDLCK is not set, the WDT is disabled by clearing the WDTE bit. The WDT is enabled following any reset. The PCA0 counter clock defaults to the system clock divided by 12, PCA0L defaults to 0x00, and PCA0CPL5 defaults to 0x00. Using Equation 26.5, this results in a WDT timeout interval of 256 PCA clock cycles, or 3072 system clock cycles. Table 26.3 lists some example timeout intervals for typical system clocks.
Table 26.3. Watchdog Timer Timeout Intervals
System Clock (Hz) 24,500,000 24,500,000 24,500,000 3,062,500* 3,062,500* 3,062,500 32,000 32,000 32,000
*
PCA0CPL5 255 128 32 255 128 32 255 128 32
Timeout Interval (ms) 32.1 16.2 4.1 257 129.5 33.1 24576 12384 3168
*Note: Internal SYSCLK reset frequency = Internal Oscillator divided by 8.
Rev. 1.0
305
C8051F91x-C8051F90x
26.5. Register Descriptions for PCA0
Following are detailed descriptions of the special function registers related to the operation of the PCA.
SFR Definition 26.1. PCA0CN: PCA Control
Bit Name Type Reset 7 CF R/W 0 6 CR R/W 0 5 CCF5 R/W 0 4 CCF4 R/W 0 3 CCF3 R/W 0 2 CCF2 R/W 0 1 CCF1 R/W 0 0 CCF0 R/W 0
SFR Page = 0x0; SFR Address = 0xD8; Bit-Addressable Bit Name Function 7 CF PCA Counter/Timer Overflow Flag. Set by hardware when the PCA Counter/Timer overflows from 0xFFFF to 0x0000. When the Counter/Timer Overflow (CF) interrupt is enabled, setting this bit causes the CPU to vector to the PCA interrupt service routine. This bit is not automatically cleared by hardware and must be cleared by software. 6 CR PCA Counter/Timer Run Control. This bit enables/disables the PCA Counter/Timer. 0: PCA Counter/Timer disabled. 1: PCA Counter/Timer enabled. 5:0 CCF[5:0] PCA Module n Capture/Compare Flag. These bits are set by hardware when a match or capture occurs in the associated PCA Module n. When the CCFn interrupt is enabled, setting this bit causes the CPU to vector to the PCA interrupt service routine. This bit is not automatically cleared by hardware and must be cleared by software.
306
Rev. 1.0
C8051F91x-C8051F90x
SFR Definition 26.2. PCA0MD: PCA Mode
Bit Name Type Reset 7 CIDL R/W 0 6 WDTE R/W 1 5 WDLCK R/W 0 R 0 4 3 CPS2 R/W 0 2 CPS1 R/W 0 1 CPS0 R/W 0 0 ECF R/W 0
SFR Page = 0x0; SFR Address = 0xD9 Bit Name 7 CIDL PCA Counter/Timer Idle Control.
Function
Specifies PCA behavior when CPU is in Idle Mode. 0: PCA continues to function normally while the system controller is in Idle Mode. 1: PCA operation is suspended while the system controller is in Idle Mode. 6 WDTE Watchdog Timer Enable. If this bit is set, PCA Module 2 is used as the watchdog timer. 0: Watchdog Timer disabled. 1: PCA Module 2 enabled as Watchdog Timer. 5 WDLCK Watchdog Timer Lock. This bit locks/unlocks the Watchdog Timer Enable. When WDLCK is set, the Watchdog Timer may not be disabled until the next system reset. 0: Watchdog Timer Enable unlocked. 1: Watchdog Timer Enable locked. 4 3:1 Unused Read = 0b, Write = don't care. These bits select the timebase source for the PCA counter 000: System clock divided by 12 001: System clock divided by 4 010: Timer 0 overflow 011: High-to-low transitions on ECI (max rate = system clock divided by 4) 100: System clock 101: External clock divided by 8 (synchronized with the system clock) 110: SmaRTClock divided by 8 (synchronized with the system clock and only available on `F912 and `F902 devices -- this setting is reserved on all other devices) 111: Reserved 0 ECF PCA Counter/Timer Overflow Interrupt Enable. This bit sets the masking of the PCA Counter/Timer Overflow (CF) interrupt. 0: Disable the CF interrupt. 1: Enable a PCA Counter/Timer Overflow interrupt request when CF (PCA0CN.7) is set.
Note: When the WDTE bit is set to 1, the other bits in the PCA0MD register cannot be modified. To change the contents of the PCA0MD register, the Watchdog Timer must first be disabled.
CPS[2:0] PCA Counter/Timer Pulse Select.
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SFR Definition 26.3. PCA0PWM: PCA PWM Configuration
Bit Name Type Reset 7 ARSEL R/W 0 6 ECOV R/W 0 5 COVF R/W 0 R 0 R 0 R 0 0 4 3 2 1 0
CLSEL[1:0] R/W 0
SFR Page = 0x0; SFR Address = 0xDF Bit Name 7 ARSEL Auto-Reload Register Select.
Function
This bit selects whether to read and write the normal PCA capture/compare registers (PCA0CPn), or the Auto-Reload registers at the same SFR addresses. This function is used to define the reload value for 9, 10, and 11-bit PWM modes. In all other modes, the Auto-Reload registers have no function. 0: Read/Write Capture/Compare Registers at PCA0CPHn and PCA0CPLn. 1: Read/Write Auto-Reload Registers at PCA0CPHn and PCA0CPLn. 6 ECOV Cycle Overflow Interrupt Enable. This bit sets the masking of the Cycle Overflow Flag (COVF) interrupt. 0: COVF will not generate PCA interrupts. 1: A PCA interrupt will be generated when COVF is set. Cycle Overflow Flag. This bit indicates an overflow of the 8th, 9th, 10th, or 11th bit of the main PCA counter (PCA0). The specific bit used for this flag depends on the setting of the Cycle Length Select bits. The bit can be set by hardware or software, but must be cleared by software. 0: No overflow has occurred since the last time this bit was cleared. 1: An overflow has occurred since the last time this bit was cleared. 4:2 Unused Unused. Read = 000b; Write = don't care. 1:0 CLSEL[1:0] Cycle Length Select. When 16-bit PWM mode is not selected, these bits select the length of the PWM cycle, between 8, 9, 10, or 11 bits. This affects all channels configured for PWM which are not using 16-bit PWM mode. These bits are ignored for individual channels configured to16-bit PWM mode. 00: 8 bits. 01: 9 bits. 10: 10 bits. 11: 11 bits.
5
COVF
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SFR Definition 26.4. PCA0CPMn: PCA Capture/Compare Mode
Bit Name Type Reset 7 PWM16n R/W 0 6 ECOMn R/W 0 5 CAPPn R/W 0 4 CAPNn R/W 0 3 MATn R/W 0 2 TOGn R/W 0 1 PWMn R/W 0 0 ECCFn R/W 0
SFR Address, Page: PCA0CPM0 = 0xDA, 0x0; PCA0CPM1 = 0xDB, 0x0; PCA0CPM2 = 0xDC, 0x0 PCA0CPM3 = 0xDD, 0x0; PCA0CPM4 = 0xDE, 0x0; PCA0CPM5 = 0xCE, 0x0 Bit Name Function 7 PWM16n 16-bit Pulse Width Modulation Enable. This bit enables 16-bit mode when Pulse Width Modulation mode is enabled. 0: 8 to 11-bit PWM selected. 1: 16-bit PWM selected. 6 5 4 3 ECOMn CAPPn CAPNn MATn Comparator Function Enable. This bit enables the comparator function for PCA module n when set to 1. Capture Positive Function Enable. This bit enables the positive edge capture for PCA module n when set to 1. Capture Negative Function Enable. This bit enables the negative edge capture for PCA module n when set to 1. Match Function Enable. This bit enables the match function for PCA module n when set to 1. When enabled, matches of the PCA counter with a module's capture/compare register cause the CCFn bit in PCA0MD register to be set to logic 1. 2 TOGn Toggle Function Enable. This bit enables the toggle function for PCA module n when set to 1. When enabled, matches of the PCA counter with a module's capture/compare register cause the logic level on the CEXn pin to toggle. If the PWMn bit is also set to logic 1, the module operates in Frequency Output Mode. 1 PWMn Pulse Width Modulation Mode Enable. This bit enables the PWM function for PCA module n when set to 1. When enabled, a pulse width modulated signal is output on the CEXn pin. 8 to 11-bit PWM is used if PWM16n is cleared; 16-bit mode is used if PWM16n is set to logic 1. If the TOGn bit is also set, the module operates in Frequency Output Mode. 0 ECCFn Capture/Compare Flag Interrupt Enable. This bit sets the masking of the Capture/Compare Flag (CCFn) interrupt. 0: Disable CCFn interrupts. 1: Enable a Capture/Compare Flag interrupt request when CCFn is set.
Note: When the WDTE bit is set to 1, the PCA0CPM5 register cannot be modified, and module 5 acts as the watchdog timer. To change the contents of the PCA0CPM5 register or the function of module 5, the Watchdog Timer must be disabled.
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SFR Definition 26.5. PCA0L: PCA Counter/Timer Low Byte
Bit Name Type Reset R/W 0 R/W 0 R/W 0 7 6 5 4 PCA0[7:0] R/W 0 R/W 0 R/W 0 R/W 0 R/W 0 3 2 1 0
SFR Page = 0x0; SFR Address = 0xF9 Bit Name 7:0 PCA0[7:0] PCA Counter/Timer Low Byte.
Function
The PCA0L register holds the low byte (LSB) of the 16-bit PCA Counter/Timer.
Note: When the WDTE bit is set to 1, the PCA0L register cannot be modified by software. To change the contents of the PCA0L register, the Watchdog Timer must first be disabled.
SFR Definition 26.6. PCA0H: PCA Counter/Timer High Byte
Bit Name Type Reset R/W 0 R/W 0 R/W 0 7 6 5 4 3 2 1 0
PCA0[15:8] R/W 0 R/W 0 R/W 0 R/W 0 R/W 0
SFR Page = 0x0; SFR Address = 0xFA Bit Name 7:0 PCA0[15:8] PCA Counter/Timer High Byte.
Function
The PCA0H register holds the high byte (MSB) of the 16-bit PCA Counter/Timer. Reads of this register will read the contents of a "snapshot" register, whose contents are updated only when the contents of PCA0L are read (see Section 26.1).
Note: When the WDTE bit is set to 1, the PCA0H register cannot be modified by software. To change the contents of the PCA0H register, the Watchdog Timer must first be disabled.
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SFR Definition 26.7. PCA0CPLn: PCA Capture Module Low Byte
Bit Name Type Reset R/W 0 R/W 0 R/W 0 7 6 5 4 3 2 1 0
PCA0CPn[7:0] R/W 0 R/W 0 R/W 0 R/W 0 R/W 0
SFR Addresses: PCA0CPL0 = 0xFB, PCA0CPL1 = 0xE9, PCA0CPL2 = 0xEB, PCA0CPL3 = 0xED, PCA0CPL4 = 0xFD, PCA0CPL5 = 0xD2 SFR Pages: Bit 7:0 PCA0CPL0 = 0x0, PCA0CPL1 = 0x0, PCA0CPL2 = 0x0, PCA0CPL3 = 0x0, PCA0CPL4 = 0x0, PCA0CPL5 = 0x0 Name Function The PCA0CPLn register holds the low byte (LSB) of the 16-bit capture module n. This register address also allows access to the low byte of the corresponding PCA channel's auto-reload value for 9, 10, or 11-bit PWM mode. The ARSEL bit in register PCA0PWM controls which register is accessed.
Note: A write to this register will clear the module's ECOMn bit to a 0.
PCA0CPn[7:0] PCA Capture Module Low Byte.
SFR Definition 26.8. PCA0CPHn: PCA Capture Module High Byte
Bit Name Type Reset R/W 0 R/W 0 R/W 0 7 6 5 4 3 2 1 0
PCA0CPn[15:8] R/W 0 R/W 0 R/W 0 R/W 0 R/W 0
SFR Addresses: PCA0CPH0 = 0xFC, PCA0CPH1 = 0xEA, PCA0CPH2 = 0xEC, PCA0CPH3 = 0xEE, PCA0CPH4 = 0xFE, PCA0CPH5 = 0xD3 SFR Pages: Bit PCA0CPH0 = 0x0, PCA0CPH1 = 0x0, PCA0CPH2 = 0x0, PCA0CPH3 = 0x0, PCA0CPH4 = 0x0, PCA0CPH5 = 0x0 Name Function The PCA0CPHn register holds the high byte (MSB) of the 16-bit capture module n. This register address also allows access to the high byte of the corresponding PCA channel's auto-reload value for 9, 10, or 11-bit PWM mode. The ARSEL bit in register PCA0PWM controls which register is accessed.
Note: A write to this register will set the module's ECOMn bit to a 1.
7:0 PCA0CPn[15:8] PCA Capture Module High Byte.
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27. C2 Interface
C8051F91x-C8051F90x devices include an on-chip Silicon Labs 2-Wire (C2) debug interface to allow Flash programming and in-system debugging with the production part installed in the end application. The C2 interface uses a clock signal (C2CK) and a bi-directional C2 data signal (C2D) to transfer information between the device and a host system. See the C2 Interface Specification for details on the C2 protocol.
27.1. C2 Interface Registers
The following describes the C2 registers necessary to perform Flash programming through the C2 interface. All C2 registers are accessed through the C2 interface as described in the C2 Interface Specification.
C2 Register Definition 27.1. C2ADD: C2 Address
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
C2ADD[7:0] R/W 0 0 0 0
Bit
Name
Function The C2ADD register is accessed via the C2 interface to select the target Data register for C2 Data Read and Data Write commands. Address 0x00 0x01 0x02 0xB4 Description Selects the Device ID register for Data Read instructions Selects the Revision ID register for Data Read instructions Selects the C2 Flash Programming Control register for Data Read/Write instructions Selects the C2 Flash Programming Data register for Data Read/Write instructions
7:0 C2ADD[7:0] C2 Address.
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C2 Register Definition 27.2. DEVICEID: C2 Device ID
Bit Name Type Reset 0 0 0 1 7 6 5 4 3 2 1 0
DEVICEID[7:0] R/W 0 1 0 0
C2 Address: 0x00 Bit Name 7:0 DEVICEID[7:0] Device ID.
Function This read-only register returns the 8-bit device ID: 0x1F.
C2 Register Definition 27.3. REVID: C2 Revision ID
Bit Name Type Reset Varies Varies Varies Varies 7 6 5 4 3 2 1 0
REVID[7:0] R/W Varies Varies Varies Varies
C2 Address: 0x01 Bit Name 7:0 REVID[7:0] Revision ID.
Function This read-only register returns the 8-bit revision ID. For example: 0x00 = Revision A.
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C2 Register Definition 27.4. FPCTL: C2 Flash Programming Control
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
FPCTL[7:0] R/W 0 0 0 0
C2 Address: 0x02 Bit Name 7:0
Function This register is used to enable Flash programming via the C2 interface. To enable C2 Flash programming, the following codes must be written in order: 0x02, 0x01. Note that once C2 Flash programming is enabled, a system reset must be issued to resume normal operation.
FPCTL[7:0] Flash Programming Control Register.
C2 Register Definition 27.5. FPDAT: C2 Flash Programming Data
Bit Name Type Reset 0 0 0 0 7 6 5 4 3 2 1 0
FPDAT[7:0] R/W 0 0 0 0
C2 Address: 0xB4 Bit Name 7:0
Function This register is used to pass Flash commands, addresses, and data during C2 Flash accesses. Valid commands are listed below. Code 0x06 0x07 0x08 0x03 Command Flash Block Read Flash Block Write Flash Page Erase Device Erase
FPDAT[7:0] C2 Flash Programming Data Register.
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27.2. C2 Pin Sharing
The C2 protocol allows the C2 pins to be shared with user functions so that in-system debugging and Flash programming may be performed. This is possible because C2 communication is typically performed when the device is in the halt state, where all on-chip peripherals and user software are stalled. In this halted state, the C2 interface can safely "borrow" the C2CK (RST) and C2D pins. In most applications, external resistors are required to isolate C2 interface traffic from the user application. A typical isolation configuration is shown in Figure 27.1.
C8051Fxxx
RST (a) Input (b) Output (c)
C2CK C2D
C2 Interface Master
Figure 27.1. Typical C2 Pin Sharing
The configuration in Figure 27.1 assumes the following: 1. The user input (b) cannot change state while the target device is halted. 2. The RST pin on the target device is used as an input only. Additional resistors may be necessary depending on the specific application.
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DOCUMENT CHANGE LIST
Revision 0.2 to Revision 1.0

Updated specification tables to remove TBDs. Updated power management section to indicate that the low power or precision oscillator must be selected when entering sleep or suspend mode. Updated Port I/O chapter with additional clarification on 5 V and 3.3 V tolerance. Updated QFN-42 landing diagram and stencil recommendations. Updated description of ADC0 12-bit mode.
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NOTES:
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CONTACT INFORMATION
Silicon Laboratories Inc.
400 West Cesar Chavez Austin, TX 78701 Please visit the Silicon Labs Technical Support web page: https://www.silabs.com/support/pages/contacttechnicalsupport.aspx and register to submit a technical support request.
The information in this document is believed to be accurate in all respects at the time of publication but is subject to change without notice. Silicon Laboratories assumes no responsibility for errors and omissions, and disclaims responsibility for any consequences resulting from the use of information included herein. Additionally, Silicon Laboratories assumes no responsibility for the functioning of undescribed features or parameters. Silicon Laboratories reserves the right to make changes without further notice. Silicon Laboratories makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does Silicon Laboratories assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation consequential or incidental damages. Silicon Laboratories products are not designed, intended, or authorized for use in applications intended to support or sustain life, or for any other application in which the failure of the Silicon Laboratories product could create a situation where personal injury or death may occur. Should Buyer purchase or use Silicon Laboratories products for any such unintended or unauthorized application, Buyer shall indemnify and hold Silicon Laboratories harmless against all claims and damages. Silicon Laboratories and Silicon Labs are trademarks of Silicon Laboratories Inc. Other products or brandnames mentioned herein are trademarks or registered trademarks of their respective holders.
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