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| HIGH-SPEED 3.3V 16K x 16 DUAL-PORT STATIC RAM Features True Dual-Ported memory cells which allow simultaneous reads of the same memory location High-speed access - Commercial: 25/35/55ns (max.) Low-power operation - IDT70V26S Active: 300mW (typ.) Standby: 3.3mW (typ.) - IDT70V26L Active: 300mW (typ.) Standby: 660W (typ.) Separate upper-byte and lower-byte control for multiplexed bus compatibility x IDT70V26S/L x x x x x x x x x x x IDT70V26 easily expands data bus width to 32 bits or more using the Master/Slave select when cascading more than one device M/S = VIH for BUSY output flag on Master M/S = VIL for BUSY input on Slave On-chip port arbitration logic Full on-chip hardware support of semaphore signaling between ports Fully asynchronous operation from either port TTL-compatible, single 3.3V (0.3V) power supply Available in 84-pin PGA and PLCC Industrial temperature range (-40C to +85C) is available for selected speeds Functional Block Diagram R/WL UBL R/WR UBR LBL CEL OEL LBR CER OER I/O8L-I/O15L I/O Control I/O0L-I/O7L BUSYL A13L A0L (1,2) I/O8R-I/O15R I/O Control I/O0R-I/O7R BUSYR Address Decoder 14 (1,2) MEMORY ARRAY 14 Address Decoder A13R A0R CEL ARBITRATION SEMAPHORE LOGIC CER SEML M/S NOTES: 1. (MASTER): BUSY is output; (SLAVE): BUSY is input. 2. BUSY outputs are non-tri-stated push-pull. SEMR 2945 drw 01 JUNE 2000 1 (c)2000 Integrated Device Technology, Inc. DSC 2945/13 IDT70V26S/L High-Speed 16K x 16 Dual-Port Static RAM Industrial and Commercial Temperature Ranges Description The IDT70V26 is a high-speed 16K x 16 Dual-Port Static RAM. The IDT70V26 is designed to be used as a stand-alone 256K-bit DualPort RAM or as a combination MASTER/SLAVE Dual-Port RAM for 32bit-or-more word systems. Using the IDT MASTER/SLAVE Dual-Port RAM approach in 32-bit or wider memory system applications results in full-speed, error-free operation without the need for additional discrete logic. This device provides two independent ports with separate control, address, and I/O pins that permit independent, asynchronous access for reads or writes to any location in memory. An automatic power down feature controlled by CE permits the on-chip circuitry of each port to enter a very low standby power mode. Fabricated using IDT's CMOS high-performance technology, these devices typically operate on only 300mW of power. The IDT70V26 is packaged in a ceramic 84-pin PGA and 84-Pin PLCC. Pin Configurations(1,2,3) OEL VCC R/WL I/O7L I/O6L I/O5L I/O4L I/O3L I/O2L GND I/O1L I/O0L SEML CEL A13L A12L A11L UBL INDEX 11 10 9 8 7 6 I/O8L I/O9L I/O10L I/O11L I/O12L I/O13L GND I/O14L I/O15L VCC GND I/O0R I/O1R I/O2R VCC I/O3R I/O4R I/O5R I/O6R I/O7R I/O8R 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 5 4 3 2 1 84 83 82 81 80 79 78 77 76 75 74 73 72 71 70 69 68 67 IDT70V26J J84-1(4) 84-Pin PLCC Top View(5) 66 65 64 63 62 61 60 59 58 57 56 55 LBL A10L A9L A8L A7L A6L A5L A4L A3L A2L A1L A0L BUSYL GND M/S BUSYR A0R A1R A2R A3R A4R A5R A6R A7R 2945 drw 02 54 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 GND I/O11R I/O12R I/O13R I/O14R I/O10R I/O15R OER R/WR GND SEMR CER UBR LBR A13R A12R A11R NOTES: 1. All VCC pins must be connected to power supply. 2. All GND pins must be connected to ground supply. 3. Package body is approximately 1.15 in x 1.15 in x .17 in. 4. This package code is used to reference the package diagram. 5. This text does not indicate orientation of the actual part-marking. I/O9R 6.42 2 A10R A9R A8R IDT70V26S/L High-Speed 16K x 16 Dual-Port Static RAM Industrial and Commercial Temperature Ranges Pin Configurations(1,2,3) (con't.) 63 61 60 58 55 54 51 48 46 45 42 11 I/O7L 66 I/O5L 64 I/O4L 62 I/O2L 59 I/O0L 56 OEL 49 SEML 50 LBL 47 A12L 44 A11L 43 A8L 40 10 I/O10L 67 I/O8L 65 I/O6L I/O3L I/O1L 57 UBL 53 CEL 52 A13L A10L A9L 41 39 A6L 09 I/O11L 69 I/O9L 68 GND VCC R/WL A7L 38 37 A5L 08 I/O13L 72 I/O12L 71 73 33 A4L 35 A3L 34 07 I/O15L 75 I/O14L 70 VCC 74 BUSYL IDT70V26G G84-3(4) 84-Pin PGA Top View(5) 32 A1L 31 A0L 36 06 I/O0R 76 GND 77 GND 78 GND 28 M/S 29 A2L 30 05 I/O1R 79 I/O2R 80 VCC A1R A0R 26 BUSYR 27 04 I/O3R 81 I/O4R 83 7 11 12 A3R 23 A2R 25 03 I/O5R 82 1 I/O7R 2 5 GND 8 GND 10 SEMR 14 17 20 A6R 22 A4R 24 02 I/O6R 84 3 I/O9R I/O10R 4 I/O13R 6 I/O15R 9 R/WR 15 UBR 13 A12R 16 A9R 18 A7R 19 A5R 21 01 I/O8R A I/O11R B I/O12R C I/O14R D OER E LBR F CER G A13R H A11R J A10R K A8R L 2945 drw 03 Index NOTES: 1. All VCC pins must be connected to power supply. 2. All GND pins must be connected to ground supply. 3. Package body is approximately 1.12 in x 1.12 in x .16 in. 4. This package code is used to reference the package diagram. 5. This text does not indicate orientation of the actual part-marking. Pin Names Left Port CEL R/WL OEL A0L - A13L I/O0L - I/O15L SEML UBL LBL BUSYL CER R/WR OER A0R - A13R I/O0R - I/O15R SEMR UBR LBR BUSYR M/S VCC GND Right Port Chip Enable Read/Write Enable Output Enable Address Data Input/Output Semaphore Enable Upper Byte Select Lower Byte Select Busy Flag Master or Slave Select Power Ground 2945 tbl 01 Names 6.42 3 IDT70V26S/L High-Speed 16K x 16 Dual-Port Static RAM Industrial and Commercial Temperature Ranges Truth Table I Non-Contention Read/Write Control Inputs(1) CE H X L L L L L L X R/W X X L L L H H H X OE X X X X X L L L H UB X H L H L L H L X LB X H H L L H L L X SEM H H H H H H H H X I/O8-15 High-Z High-Z DATAIN High-Z DATAIN DATAOUT High-Z DATAOUT High-Z Outputs I/O0-7 High-Z High-Z High-Z DATAIN DATAIN High-Z DATAOUT DATAOUT High-Z Mode Deselected: Power-Down Both Bytes Deselected: Power-Down Write to Upper Byte Only Write to Lower Byte Only Write to Both Bytes Read Upper Byte Only Read Lower Byte Only Read Both Bytes Outputs Disabled 2945 tbl 02 NOTE: 1. A0L -- A13L A0R -- A13R Truth Table II Semaphore Read/Write Control(1) Inputs(1) CE H X H X L L R/W H H X X OE L L X X X X UB X H X H L X LB X H X H X L SEM L L L L L L I/O8-15 DATAOUT DATAOUT DATAIN DATAIN ____ Outputs I/O0-7 DATAOUT DATAOUT DATAIN DATAIN ____ Mode Read Data in Semaphore Flag Read Data in Semaphore Flag Write I/O0 into Semaphore Flag Write I/O0 into Semaphore Flag Not Allowed Not Allowed 2945 tbl 03 ____ ____ NOTE: 1. There are eight semaphore flags written to via I/O0 and read from all I/O's (I/O0-I/O15). These eight semaphores are addressed by A0-A2. 6.42 4 IDT70V26S/L High-Speed 16K x 16 Dual-Port Static RAM Industrial and Commercial Temperature Ranges Absolute Maximum Ratings(1) Symbol VTERM(2) Rating Terminal Voltage with Respect to GND Temperature Under Bias Storage Temperature DC Output Current Commercial & Industrial -0.5 to +4.6 Unit V Maximum Operating Temperature and Supply Voltage(1,2) Grade Ambient Temperature Commercial 0OC to +70OC -40OC to +85OC 0V 0V 3.3V + 0.3 3.3V + 0.3 2945 tbl 05 GND Vcc TBIAS TSTG IOUT -55 to +125 -65 to +150 50 o C C Industrial o mA 2945 tbl 04 NOTES: 1. This is the parameter TA. This is the "instant on" case temperature. 2. Industrial temperature: for specific speeds, packages and powers contact your sales office. NOTES: 1. Stresses greater than those listed under ABSOLUTE MAXIMUM RATINGS may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability. 2. VTERM must not exceed Vcc + 0.3V for more than 25% of the cycle time or 10ns maximum, and is limited to < 20mA for the period of VTERM > Vcc + 0.3V. Recommended DC Operating Conditions(2) Symbol VCC GND VIH Parameter Supply Voltage Ground Input High Voltage Input Low Voltage Min. 3.0 0 2.0 -0.3 (1) Typ. 3.3 0 ____ ____ Max. 3.6 0 VCC + 0.3 0.8 (2) Unit V V V V 2945 tbl 06 Capacitance(1) (TA = +25C, f = 1.0MHz) Symbol CIN COUT Parameter Input Capacitance Output Capacitance Conditions(2) VIN = 3dV VOUT = 3dV Max. 9 10 Unit pF pF 2945 tbl 07 VIL NOTES: 1. VIL > -1.5V for pulse width less than 10ns. 2. VTERM must not exceed Vcc + 0.3V. NOTES: 1. This parameter is determined by device characterization but is not production tested. 2. 3dV represents the interpolated capacitance when the input and output signals switch from 0V to 3V or from 3V to 0V. DC Electrical Characteristics Over the Operating Temperature and Supply Voltage Range (VCC = 3.3V 0.3V) 70V26S Symbol |ILI| |ILO| VOL VOH Parameter Input Leakage Current(1) Output Leakage Current Output Low Voltage Output High Voltage Test Conditions VCC = 3.6V, VIN = 0V to VCC CE = VIH, VOUT = 0V to VCC IOL = +4mA IOH = -4mA Min. ___ 70V26L Min. ___ Max. 10 10 0.4 ___ Max. 5 5 0.4 ___ Unit A A V V 2945 tbl 08 ___ ___ ___ ___ 2.4 2.4 NOTE: 1. At VCC < 2.0V, input leakages are undefined. 6.42 5 IDT70V26S/L High-Speed 16K x 16 Dual-Port Static RAM Industrial and Commercial Temperature Ranges DC Electrical Characteristics Over the Operating Temperature and Supply Voltage Range(1,6) (VCC = 3.3V 0.3V) 70V26X25 Com'l Only Symbol ICC Parameter Dynamic Operating Current (Both Ports Active) Test Condition CE = VIL, Outputs Disabled SEM = VIH f = fMAX(3) Version COM'L IND COM'L IND COM'L IND COM'L IND COM'L IND S L S L S L S L S L S L S L S L S L S L Typ.(2) 100 100 ____ ____ 70V26X35 Com'l Only Typ.(2) 90 90 ____ ____ 70V26X55 Com'l Only Typ.(2) 90 90 ____ ____ Max. 170 140 ____ ____ Max. 140 120 ____ ____ Max. 140 120 ____ ____ Unit mA mA mA mA mA mA mA mA mA mA ISB1 Standby Current (Both Ports - TTL Level Inputs) CER = CEL = VIH SEMR = SEML = VIH f = fMAX(3) 14 12 ____ ____ 30 24 ____ ____ 12 10 ____ ____ 30 24 ____ ____ 12 10 ____ ____ 30 24 ____ ____ ISB2 Standby Current (One Port - TTL Level Inputs) CE"A" = VIL and CE"B" = VIH(5) Active Port Outputs Disabled, f=fMAX(3) SEMR = SEML = VIH Both Ports CEL and CER > VCC - 0.2V, VIN > VCC - 0.2V or VIN < 0.2V, f = 0(4) SEMR = SEML > VCC - 0.2V CE"A" < 0.2V and CE"B" > VCC - 0.2V(5) SEMR = SEML > VCC - 0.2V VIN > VCC - 0.2V or VIN < 0.2V Active Port Outputs Disabled, f = fMAX(3) 50 50 ____ ____ 95 85 ____ ____ 45 45 ____ ____ 87 75 ____ ____ 45 45 ____ ____ 87 75 ____ ____ ISB3 Full Standby Current (Both Ports CMOS Level Inputs) 1.0 0.2 ____ ____ 6 3 ____ ____ 1.0 0.2 ____ ____ 6 3 ____ ____ 1.0 0.2 ____ ____ 6 3 ____ ____ ISB4 Full Standby Current (One Port CMOS Level Inputs) 60 60 ____ ____ 90 80 ____ ____ 55 55 ____ ____ 85 74 ____ ____ 55 55 ____ ____ 85 74 ____ ____ NOTES: 1. 'X' in part number indicates power rating (S or L) 2. VCC = 3.3V, TA = +25C, and are not production tested. ICCDC = 80mA (Typ.) 3. At f = fMAX, address and control lines (except Output Enable) are cycling at the maximum frequency read cycle of 1/tRC, and using "AC Test Conditions" of input levels of GND to 3V. 4. f = 0 means no address or control lines change. 5. Port "A" may be either left or right port. Port "B" is the opposite from port "A". 6. Industrial temperature: for specific speeds, packages and powers contact your sales office. 2945 tbl 09 AC Test Conditions Input Pulse Levels Input Rise/Fall Times Input Timing Reference Levels Output Reference Levels Output Load GND to 3.0V 3ns Max. 1.5V 1.5V Figures 1 and 2 2945 tbl 10 3.3V 3.3V 590 DATAOUT BUSY 435 30pF DATAOUT 435 590 5pF* 2945 drw 04 2945 drw 05 Figure 1. AC Output Test Load Figure 2. Output Test Load (for tLZ, tHZ, tWZ, tOW) * Including scope and jig. 6.42 6 IDT70V26S/L High-Speed 16K x 16 Dual-Port Static RAM Industrial and Commercial Temperature Ranges AC Electrical Characteristics Over the Operating Temperature and Supply Voltage Range(4,5) 70V26X25 Com'l Only Symbol READ CYCLE tRC tAA tACE tABE tAOE tOH tLZ tHZ tPU tPD tSOP tSAA Read Cycle Time Address Access Time Chip Enable Access Time Byte Enable Access Time (3) (3) 70V26X35 Com'l Only Min. Max. 70V26X55 Com'l Only Min. Max. Unit Parameter Min. Max. 25 ____ ____ 35 ____ ____ 55 ____ ____ ns ns ns ns ns ns ns ns ns ns ns ns 2945 tbl 11 25 25 25 15 ____ 35 35 35 20 ____ 55 55 55 30 ____ ____ ____ ____ ____ ____ ____ Output Enable Access Time Output Hold from Address Change Output Low-Z Time (1,2) Output High-Z Time (1,2) (2) (2) ____ ____ ____ 3 3 ____ 3 3 ____ 3 3 ____ ____ ____ ____ 15 ____ 20 ____ 25 ____ Chip Enable to Power Up Time 0 ____ 0 ____ 0 ____ Chip Disable to Power Down Time 25 ____ 35 ____ 50 ____ Semaphore Flag Update Pulse (OE or SEM) Semaphore Address Access Time 15 ____ 15 ____ 15 ____ 35 45 65 NOTES: 1. Transition is measured 0mV from Low- or High-impedance voltage with Output Test Load (Figure 2). 2. This parameter is guaranteed by device characterization, but is not production tested. 3. To access RAM, CE = VIL and SEM = VIH. To access semaphore, CE = VIH and SEM = VIL. 4. 'X' in part number indicates power rating (S or L). 5. Industrial temperature: for specific speeds, packages and powers contact your sales office. Timing of Power-Up Power-Down CE ICC ISB tPU 50% tPD 50% 2945 drw 06 , 6.42 7 IDT70V26S/L High-Speed 16K x 16 Dual-Port Static RAM Industrial and Commercial Temperature Ranges Waveform of Read Cycles(5) tRC ADDR tAA (4) tACE tAOE OE tABE UB, LB (4) (4) (4) CE R/W tLZ DATAOUT (1) tOH VALID DATA (4) (2) tHZ BUSYOUT tBDD (3,4) 2945 drw 07 NOTES: 1. Timing depends on which signal is asserted last, OE, CE, LB, or UB. 2. Timing depends on which signal is de-asserted first CE, OE, LB, or UB. 3. tBDD delay is required only in cases where the opposite port is completing a write operation to the same address location. For simultaneous read operations BUSY has no relation to valid output data. 4. Start of valid data depends on which timing becomes effective last tAOE, tACE, tAA or tBDD. 5. SEM = VIH. AC Electrical Characteristics Over the Operating Temperature and Supply Voltage(5,6) 70V26X25 Com'l Only Symbol WRITE CYCLE tWC tEW tAW tAS tWP tWR tDW tHZ tDH tWZ tOW tSWRD tSPS Write Cycle Time Chip Enable to End-of-Write (3) Address Valid to End-of-Write Address Set-up Time Write Pulse Width Write Recovery Time Data Valid to End-of-Write Output High-Z Time Data Hold Time (4) (1,2) (1,2) (3) 70V26X35 Com'l Only Min. Max. 70V26X55 Com'l Only Min. Max. Unit Parameter Min. Max. 25 20 20 0 20 0 15 ____ ____ 35 30 30 0 25 0 20 ____ ____ 55 45 45 0 40 0 30 ____ ____ ns ns ns ns ns ns ns ns ns ns ns ns ns 2945 tbl 12 ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ 15 ____ 20 ____ 25 ____ 0 ____ 0 ____ 0 ____ Write Enable to Output in High-Z 15 ____ 20 ____ 25 ____ Output Active from End-of-Write (1,2,4) SEM Flag Write to Read Time SEM Flag Contention Window 0 5 5 0 5 5 0 5 5 ____ ____ ____ ____ ____ ____ NOTES: 1. Transition is measured 0mV from Low- or High-impedance voltage with Output Test Load (Figure 2). 2. This parameter is guaranteed by device characterization, but is not production tested. 3. To access RAM, CE = VIL and SEM = VIH. To access semaphore, CE = VIH and SEM = VIL. Either condition must be valid for the entire tEW time. 4. The specification for tDH must be met by the device supplying write data to the RAM under all operating conditions. Although tDH and tOW values will vary over voltage and temperature, the actual tDH will always be smaller than the actual tOW. 5. 'X' in part numbers indicates power rating (S or L). 6. Industrial temperature: for specific speeds, packages and powers contact your sales office. 6.42 8 IDT70V26S/L High-Speed 16K x 16 Dual-Port Static RAM Industrial and Commercial Temperature Ranges Timing Waveform of Write Cycle No. 1, R/W Controlled Timing(1,5,8) tWC ADDRESS tHZ OE tAW CE or SEM (9) (7) CE or SEM (9) tAS (6) R/W tWZ DATAOUT (4) (7) tWP (2) tWR (3) tOW (4) tDW DATAIN tDH 2945 drw 08 Timing Waveform of Write Cycle No. 2, CE, UB, LB Controlled Timing(1,5) tWC ADDRESS tAW CE or SEM (9) (6) tAS UB or LB (9) tEW (2) tWR (3) R/W tDW DATAIN 2945 drw 09 tDH NOTES: 1. R/W or CE or UB and LB must be HIGH during all address transitions. 2. A write occurs during the overlap (tEW or tWP) of a LOW CE and a LOW R/W for memory array writing cycle. 3. tWR is measured from the earlier of CE or R/W (or SEM or R/W) going HIGH to the end of write cycle. 4. During this period, the I/O pins are in the output state and input signals must not be applied. 5. If the CE or SEM LOW transition occurs simultaneously with or after the R/W LOW transition, the outputs remain in the High-impedance state. 6. Timing depends on which enable signal is asserted last, CE or R/W. 7. This parameter is guaranteed by device characterization, but is not production tested. Transition is measured 0mV from steady state with the Output Test Load (Figure 2). 8. If OE is LOW during R/W controlled write cycle, the write pulse width must be the larger of tWP or (tWZ + tDW) to allow the I/O drivers to turn off and data to be placed on the bus for the required tDW. If OE is HIGH during an R/W controlled write cycle, this requirement does not apply and the write pulse can be as short as the specified tWP. 9. To access RAM, CE = VIL and SEM = VIH. To access semaphore, CE = VIH and SEM = VIL. tEW must be met for either condition. 6.42 9 IDT70V26S/L High-Speed 16K x 16 Dual-Port Static RAM Industrial and Commercial Temperature Ranges Timing Waveform of Semaphore Read after Write Timing, Either Side(1) tSAA A0-A2 VALID ADDRESS tAW SEM tSOP I/O0 tAS R/W tSWRD OE Write Cycle Read Cycle 2945 drw 10 tOH VALID ADDRESS tACE tWR tEW tDW DATAIN VALID tWP tDH DATAOUT VALID(2) tAOE NOTES: 1. CE = VIH or UB & LB = VIH for the duration of the above timing (both write and read cycle). 2. "DATAOUT VALID' represents all I/O's (I/O0-I/O15) equal to the semaphore value. Timing Waveform of Semaphore Write Contention(1,3,4) A0"A"-A2"A" MATCH SIDE (2) "A" R/W"A" SEM"A" tSPS A0"B"-A2"B" MATCH SIDE (2) "B" R/W"B" SEM"B" 2945 drw 11 NOTES: 1. DOR = DOL = VIL, CER = CEL = VIH, or both UB & LB = VIH. 2. All timing is the same for left and right ports. Port "A" may be either left or right port. Port "B" is the opposite from port "A". 3. This parameter is measured from R/W"A" or SEM"A" going HIGH to R/W"B" or SEM"B" going HIGH. 4. If tSPS is not satisfied, the semaphore will fall positively to one side or the other, but there is no guarantee which side will obtain the flag. 6.42 10 IDT70V26S/L High-Speed 16K x 16 Dual-Port Static RAM Industrial and Commercial Temperature Ranges AC Electrical Characteristics Over the Operating Temperature and Supply Voltage Range(6,7) 70V26X25 Com'l Only Symbol BUSY TIMING (M/S = VIH) tBAA tBDA tBAC tBDC tAPS tBDD tWH BUSY Access Time from Address Match BUSY Disable Time from Address Not Match BUSY Acce ss Time from Chip Enable Low BUSY Disab le Time from Chip Enable High Arbitration Priority Set-up Time (2) BUSY Disable to Valid Data(3) Write Hold After BUSY (5) ____ 70V26X35 Com'l Only Min. Max. 70V26X55 Com'l Only Min. Max. Unit Parameter Min. Max. 25 25 25 25 ____ ____ 35 35 35 35 ____ ____ 45 45 45 45 ____ ns ns ns ns ns ns ns ____ ____ ____ ____ ____ ____ ____ ____ ____ 5 ____ 5 ____ 5 ____ 35 ____ 40 ____ 50 ____ 20 25 25 BUSY INPUT TIMING (M/S = VIL) tWB tWH BUSY Input to Write (4) Write Hold After BUSY(5) 0 20 ____ 0 25 ____ 0 25 ____ ns ns ____ ____ ____ PORT-TO-PORT DELAY TIMING tWDD tDDD Write Pulse to Data Delay(1) Write Data Valid to Read Data Delay (1) ____ 55 50 ____ 65 60 ____ 85 80 ns ns 2945 tbl 13 ____ ____ ____ NOTES: 1. Port-to-port delay through RAM cells from writing port to reading port, refer to "Timing Waveform of Write with Port-to-Port Read and BUSY (M/S = VIH)". 2. To ensure that the earlier of the two ports wins. 3. tBDD is a calculated parameter and is the greater of 0, tWDD - tWP (actual) or tDDD - tDW (actual). 4. To ensure that the write cycle is inhibited on port "B" during contention on port "A". 5. To ensure that a write cycle is completed on port "B" after contention on port "A". 6. 'X' in part number indicates power rating (S or L). 7. Industrial temperature: for specific speeds, packages and powers contact your sales office. Timing Waveform of Write with Port-to-Port Read and BUSY(2,4,5) tWC ADDR"A" MATCH tWP R/W"A" tDW DATAIN "A" tAPS (1) ADDR"B" tBAA BUSY"B" tWDD DATAOUT "B" tDDD NOTES: 1. To ensure that the earlier of the two ports wins. tAPS is ignored for M/S = VIL (SLAVE). 2. CEL = CER = VIL 3. OE = VIL for the reading port. 4. If M/S = VIL (SLAVE), then BUSY is an input (BUSY"A" = VIH and BUSY"B" = "don't care", for this example). 5. All timing is the same for left and right ports. Port "A" may be either the left or right port. Port "B" is the port opposite from port "A". (3) tDH VALID MATCH tBDA tBDD VALID 2945 drw 12 6.42 11 IDT70V26S/L High-Speed 16K x 16 Dual-Port Static RAM Industrial and Commercial Temperature Ranges Timing Waveform of Write with BUSY tWP R/W"A" tWB BUSY"B" tWH (1) R/W"B" NOTES: 1. tWH must be met for both BUSY input (SLAVE) and output (MASTER). 2. BUSY is asserted on port "B" blocking R/W"B", until BUSY"B" goes HIGH. (2) 2945 drw 13 Waveform of BUSY Arbitration Controlled by CE Timing(1) ADDR"A" and "B" ADDRESSES MATCH CE"A" tAPS CE"B" tBAC BUSY"B" 2945 drw 14 (2) tBDC Waveform of BUSY Arbitration Cycle Controlled by Address Match Timing(1) ADDR"A" tAPS ADDR"B" tBAA BUSY"B" 2945 drw 15 (2) ADDRESS "N" MATCHING ADDRESS "N" tBDA NOTES: 1. All timing is the same for left and right ports. Port "A" may be either the left or right port. Port "B" is the port opposite from port "A". 2. If tAPS is not satisfied, the BUSY signal will be asserted on one side or the other, but there is no guarantee on which side BUSY will be asserted. 6.42 12 IDT70V26S/L High-Speed 16K x 16 Dual-Port Static RAM Industrial and Commercial Temperature Ranges Truth Table III Address BUSY Arbitration Inputs CEL X H X L CER X X H L A0L-A13L A0R-A13R NO MATCH MATCH MATCH MATCH Outputs BUSYL(1) H H H (2) BUSYR(1) H H H (2) Function Normal Normal Normal Write Inhibit(3) 2945 tbl 14 NOTES: 1. Pins BUSYL and BUSYR are both outputs when the part is configured as a master. Both are inputs when configured as a slave. BUSYX outputs on the IDT70V26 are push pull, not open drain outputs. On slaves the BUSYX input internally inhibits writes. 2. L if the inputs to the opposite port were stable prior to the address and enable inputs of this port. H if the inputs to the opposite port became stable after the address and enable inputs of this port. If tAPS is not met, either BUSYL or BUSYR = LOW will result. BUSYL and BUSYR outputs cannot be LOW simultaneously. 3. Writes to the left port are internally ignored when BUSYL outputs are driving LOW regardless of actual logic level on the pin. Writes to the right port are internally ignored when BUSYR outputs are driving LOW regardless of actual logic level on the pin. Truth Table IV Example of Semaphore Procurement Sequence(1,2,3) Functions No Action Left Port Writes "0" to Semaphore Right Port Writes "0" to Semaphore Left Port Writes "1" to Semaphore Left Port Writes "0" to Semaphore Right Port Writes "1" to Semaphore Left Port Writes "1" to Semaphore Right Port Writes "0" to Semaphore Right Port Writes "1" to Semaphore Left Port Writes "0" to Semaphore Left Port Writes "1" to Semaphore D0 - D15 Left 1 0 0 1 1 0 1 1 1 0 1 D0 - D15 Right 1 1 1 0 0 1 1 0 1 1 1 Semaphore free Left port has semaphore token No change. Right side has no write access to semaphore Right port obtains semaphore token No change. Left port has no write access to semaphore Left port obtains semaphore token Semaphore free Right port has semaphore token Semaphore free Left port has semaphore token Semaphore free 2945 tbl 15 Status NOTE: 1. This table denotes a sequence of events for only one of the eight semaphores on the IDT70V26. 2. There are eight semaphore flags written to via I/O0 and read from all I/O's (I/O0-I/O15). These eight semaphores are addressed by A0-A2. 3. CE = VIH, SEM = VIL to access the semaphores. Refer to the Semaphore Read/Write Control Truth Table. Functional Description The IDT70V26 provides two ports with separate control, address and I/O pins that permit independent access for reads or writes to any location in memory. The IDT70V26 has an automatic power down feature controlled by CE. The CE controls on-chip power down circuitry that permits the respective port to go into a standby mode when not selected (CE HIGH). When a port is enabled, access to the entire memory array is permitted. Busy Logic Busy Logic provides a hardware indication that both ports of the RAM have accessed the same location at the same time. It also allows one of the two accesses to proceed and signals the other side that the RAM is "busy". The BUSY pin can then be used to stall the access until the operation on the other side is completed. If a write operation has been attempted from the side that receives a BUSY indication, the write signal is gated internally to prevent the write from proceeding. The use of BUSY logic is not required or desirable for all applications. In some cases it may be useful to logically OR the BUSY outputs together and use any BUSY indication as an interrupt source to flag an illegal or illogical operation. If the write inhibit function of BUSY logic is not desirable, the BUSY logic can be disabled by placing the part in slave mode with the M/S pin. Once in slave mode the BUSY pin operates solely as a write inhibit input pin. Normal operation can be programmed by tying the BUSY pins HIGH. If desired, unintended 6.42 13 IDT70V26S/L High-Speed 16K x 16 Dual-Port Static RAM Industrial and Commercial Temperature Ranges write operations can be prevented to a port by tying the BUSY pin for that port LOW. The BUSY outputs on the IDT 70V26 RAM in master mode, are push-pull type outputs and do not require pull up resistors to operate. If these RAMs are being expanded in depth, then the BUSY indication for the resulting array requires the use of an external AND gate. Width Expansion with BUSY Logic Master/Slave Arrays When expanding an IDT70V26 RAM array in width while using BUSY logic, one master part is used to decide which side of the RAM array will receive a BUSY indication, and to output that indication. Any DECODER MASTER CE Dual Port RAM BUSYL BUSYR SLAVE CE Dual Port RAM BUSYL BUSYR BUSYL MASTER CE Dual Port RAM BUSYL BUSYR SLAVE CE Dual Port RAM BUSYL BUSYR BUSYR 2945 drw 16 Figure 3. Busy and chip enable routing for both width and depth expansion with IDT70V26 RAMs. number of slaves to be addressed in the same address range as the master use the BUSY signal as a write inhibit signal. Thus on the IDT70V26 SRAM the BUSY pin is an output if the part is used as a master (M/S pin = H), and the BUSY pin is an input if the part used as a slave (M/S pin = L) as shown in Figure 3. If two or more master parts were used when expanding in width, a split decision could result with one master indicating BUSY on one side of the array and another master indicating BUSY on one other side of the array. This would inhibit the write operations from one port for part of a word and inhibit the write operations from the other port for word. The BUSY arbitration, on a master, is based on the chip enable and address signals only. It ignores whether an access is a read or write. In a master/slave array, both address and chip enable must be valid long enough for a BUSY flag to be output from the master before the actual write pulse can be initiated with either the R/W signal or the byte enables. Failure to observe this timing can result in a glitched internal write inhibit signal and corrupted data in the slave. are completely independent of each other. This means that the activity on the left port in no way slows the access time of the right port. Both ports are identical in function to standard CMOS Static RAM and can be read from, or written to, at the same time with the only possible conflict arising from the simultaneous writing of, or a simultaneous READ/WRITE of, a non-semaphore location. Semaphores are protected against such ambiguous situations and may be used by the system program to avoid any conflicts in the non-semaphore portion of the Dual-Port SRAM. These devices have an automatic powerdown feature controlled by CE, the Dual-Port SRAM enable, and SEM, the semaphore enable. The CE and SEM pins control on-chip power down circuitry that permits the respective port to go into standby mode when not selected. This is the condition which is shown in Truth Table I where CE and SEM are both HIGH. Systems which can best use the IDT70V26 contain multiple processors or controllers and are typically very high-speed systems which are software controlled or software intensive. These systems can benefit from a performance increase offered by the IDT70V26's hardware semaphores, which provide a lockout mechanism without requiring complex programming. Software handshaking between processors offers the maximum in system flexibility by permitting shared resources to be allocated in varying configurations. The IDT70V26 does not use its semaphore flags to control any resources through hardware, thus allowing the system designer total flexibility in system architecture. An advantage of using semaphores rather than the more common methods of hardware arbitration is that wait states are never incurred in either processor. This can prove to be a major advantage in very high-speed systems. How the Semaphore Flags Work The semaphore logic is a set of eight latches which are independent of the Dual-Port SRAM. These latches can be used to pass a flag, or token, from one port to the other to indicate that a shared resource is in use. The semaphores provide a hardware assist for a use assignment method called "Token Passing Allocation." In this method, the state of a semaphore latch is used as a token indicating that shared resource is in use. If the left processor wants to use this resource, it requests the token by setting the latch. This processor then verifies its success in setting the latch by reading it. If it was successful, it proceeds to assume control over the shared resource. If it was not successful in setting the latch, it determines that the right side processor has set the latch first, has the token and is using the shared resource. The left processor can then either repeatedly request that semaphore's status or remove its request for that semaphore to perform another task and occasionally attempt again to gain control of the token via the set and test sequence. Once the right side has relinquished the token, the left side should succeed in gaining control. The semaphore flags are active LOW. A token is requested by writing a zero into a semaphore latch and is released when the same side writes a one to that latch. The eight semaphore flags reside within the IDT70V26 in a separate memory space from the Dual-Port SRAM. This address space is accessed by placing a LOW input on the SEM pin (which acts as a chip select for the semaphore flags) and using the other control pins (Address, OE, and R/W) as they would be used in accessing a Semaphores The IDT70V26 is an extremely fast Dual-Port 16K x 16 CMOS Static RAM with an additional 8 address locations dedicated to binary semaphore flags. These flags allow either processor on the left or right side of the Dual-Port SRAM to claim a privilege over the other processor for functions defined by the system designer's software. As an example, the semaphore can be used by one processor to inhibit the other from accessing a portion of the Dual-Port SRAM or any other shared resource. The Dual-Port SRAM features a fast access time, and both ports 6.42 14 IDT70V26S/L High-Speed 16K x 16 Dual-Port Static RAM Industrial and Commercial Temperature Ranges standard Static RAM. Each of the flags has a unique address which can be accessed by either side through address pins A0 - A2. When accessing the semaphores, none of the other address pins has any effect. When writing to a semaphore, only data pin D0 is used. If a LOW level is written into an unused semaphore location, that flag will be set to a zero on that side and a one on the other side (see Truth Table IV). That semaphore can now only be modified by the side showing the zero. When a one is written into the same location from the same side, the flag will be set to a one for both sides (unless a semaphore request from the other side is pending) and then can be written to by both sides. The fact that the side which is able to write a zero into a semaphore subsequently locks out writes from the other side is what makes semaphore flags useful in interprocessor communications. (A thorough discussion on the use of this feature follows shortly.) A zero written into the same location from the other side will be stored in the semaphore request latch for that side until the semaphore is freed by the first side. When a semaphore flag is read, its value is spread into all data bits so that a flag that is a one reads as a one in all data bits and a flag containing a zero reads as all zeros. The read value is latched into one side's output register when that side's semaphore select (SEM) and output enable (OE) signals go active. This serves to disallow the semaphore from changing state in the middle of a read cycle due to a write cycle from the other side. Because of this latch, a repeated read of a semaphore in a test loop must cause either signal (SEM or OE) to go inactive or the output will never change. A sequence WRITE/READ must be used by the semaphore in order to guarantee that no system level contention will occur. A processor requests access to shared resources by attempting to write a zero into a semaphore location. If the semaphore is already in use, the semaphore request latch will contain a zero, yet the semaphore flag will appear as one, a fact which the processor will verify by the subsequent read (see Truth Table IV). As an example, assume a processor writes a zero to the left port at a free semaphore location. On a subsequent read, the processor will verify that it has written successfully to that location and will assume control over the resource in question. Meanwhile, if a processor on the right side attempts to write a zero to the same semaphore flag it will fail, as will be verified by the fact that a one will be read from that semaphore on the right side during subsequent read. Had a sequence of READ/WRITE been used instead, system contention problems could have occurred during the gap between the read and write cycles. It is important to note that a failed semaphore request must be followed by either repeated reads or by writing a one into the same location. The reason for this is easily understood by looking at the simple logic diagram of the semaphore flag in Figure 4. Two semaphore request latches feed into a semaphore flag. Whichever latch is first to present a zero to the semaphore flag will force its side of the semaphore flag low and the other side HIGH. This condition will continue until a one is written to the same semaphore request latch. Should the other side's semaphore request latch have been written to a zero in the meantime, the semaphore flag will flip over to the other side as soon as a one is written into the first side's request latch. The second side's flag will now stay low until its semaphore request latch is written to a one. From this it is easy to understand that, if a semaphore is requested and the processor which requested it no longer needs the resource, the entire system can hang up until a one is written into that semaphore request latch. The critical case of semaphore timing is when both sides request a single token by attempting to write a zero into it at the same time. The semaphore logic is specially designed to resolve this problem. If simultaneous requests are made, the logic guarantees that only one side receives the token. If one side is earlier than the other in making the request, the first side to make the request will receive the token. If both requests arrive at the same time, the assignment will be arbitrarily made to one port or the other. One caution that should be noted when using semaphores is that semaphores alone do not guarantee that access to a resource is secure. As with any powerful programming technique, if semaphores are misused or misinterpreted, a software error can easily happen. Initialization of the semaphores is not automatic and must be handled via the initialization program at power-up. Since any semaphore request flag which contains a zero must be reset to a one, all semaphores on both sides should have a one written into them at initialization from both sides to assure that they will be free when needed. Using SemaphoresSome Examples Perhaps the simplest application of semaphores is their application as resource markers for the IDT70V26's Dual-Port RAM. Say the 16K x 16 RAM was to be divided into two 8K x 16 blocks which were to be dedicated at any one time to servicing either the left or right port. Semaphore 0 could be used to indicate the side which would control the lower section of memory, and Semaphore 1 could be defined as the indicator for the upper section of memory. To take a resource, in this example the lower 8K of Dual-Port RAM, the processor on the left port could write and then read a zero in to Semaphore 0. If this task were successfully completed (a zero was read back rather than a one), the left processor would assume control of the lower 8K. Meanwhile the right processor was attempting to gain control of the resource after the left processor, it would read back a one in response to the zero it had attempted to write into Semaphore 0. At this point, the software could choose to try and gain control of the second 8K section by writing, then reading a zero into Semaphore 1. If it succeeded in gaining control, it would lock out the left side. Once the left side was finished with its task, it would write a one to Semaphore 0 and may then try to gain access to Semaphore 1. If Semaphore 1 was still occupied by the right side, the left side could L PORT SEMAPHORE REQUEST FLIP FLOP D0 WRITE D Q R PORT SEMAPHORE REQUEST FLIP FLOP Q D D0 WRITE SEMAPHORE READ Figure 4. IDT70V26 Semaphore Logic SEMAPHORE READ , 2945 drw 17 6.42 15 IDT70V26S/L High-Speed 16K x 16 Dual-Port Static RAM Industrial and Commercial Temperature Ranges undo its semaphore request and perform other tasks until it was able to write, then read a zero into Semaphore 1. If the right processor performs a similar task with Semaphore 0, this protocol would allow the two processors to swap 8K blocks of Dual-Port RAM with each other. The blocks do not have to be any particular size and can even be variable, depending upon the complexity of the software using the semaphore flags. All eight semaphores could be used to divide the Dual-Port RAM or other shared resources into eight parts. Semaphores can even be assigned different meanings on different sides rather than being given a common meaning as was shown in the example above. Semaphores are a useful form of arbitration in systems like disk interfaces where the CPU must be locked out of a section of memory during a transfer and the I/O device cannot tolerate any wait states. With the use of semaphores, once the two devices has determined which memory area was "off-limits" to the CPU, both the CPU and the I/O devices could access their assigned portions of memory continu- ously without any wait states. Semaphores are also useful in applications where no memory "WAIT" state is available on one or both sides. Once a semaphore handshake has been performed, both processors can access their assigned RAM segments at full speed. Another application is in the area of complex data structures. In this case, block arbitration is very important. For this application one processor may be responsible for building and updating a data structure. The other processor then reads and interprets that data structure. If the interpreting processor reads an incomplete data structure, a major error condition may exist. Therefore, some sort of arbitration must be used between the two different processors. The building processor arbitrates for the block, locks it and then is able to go in and update the data structure. When the update is completed, the data structure block is released. This allows the interpreting processor to come back and read the complete data structure, thereby guaranteeing a consistent data structure. 6.42 16 IDT70V26S/L High-Speed 16K x 16 Dual-Port Static RAM Industrial and Commercial Temperature Ranges Ordering Information IDT XXXXX Device Type A Power 999 Speed A Package A Process/ Temperature Range Blank I(1) Commercial (0C to +70C) Industrial (-40C to +85C) G J 84-pin PGA (G84-3) 84-pin PLCC (J84-1) 25 35 55 Commercial Only Commercial Only Commercial Only Speed in nanoseconds S L 70V26 NOTE: 1. Industrial temperature range is available. For specific speeds, packages and powers contact your sales office. Standard Power Low Power 256K (16K x 16) 3.3V Dual-Port RAM 2945 drw 18 Datasheet Document History 3/25/99: Initiated datasheet document history Converted to new format Cosmetic and typographical corrections Page 2 and 3 Added additional notes to pin configurations Changed drawing format Page 1 Removed Preliminary Page 1 Changed 660mW to 660W Replaced IDT logo Page 5 Increased storage temperature parameter Clarified TA parameter Page 6 DC Electrical parameters-changed wording from "open" to "disabled" Changed 200mV to 0mV in notes 6/10/99: 8/6/99: 8/30/99: 11/12/99: 6/6/00: CORPORATE HEADQUARTERS 2975 Stender Way Santa Clara, CA 95054 for SALES: 800-345-7015 or 408-727-6116 fax: 408-492-8674 www.idt.com 6.42 17 for Tech Support: 831-754-4613 DualPortHelp@idt.com The IDT logo is a registered trademark of Integrated Device Technology, Inc. |
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