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| CML Microcircuits COMMUNICATION SEMICONDUCTORS CMX882 Baseband Processor for `Leisure' Radios with Data Provisional Issue D/882/7 March 2004 Full-Feature Audio-Processing, Signalling and GPS Data for Half Duplex FRS, MURS, PMR44 and GMRS `Leisure' Radios Features * Automatic signal type scanning and IRQ on detection of valid Rx signals, level or RSSI * Tone generator for caller recognition tunes * Programmable power down control * Programmable signal detection thresholds * Low Power operation with Zero Power mode * Uncommitted Aux ADC with switchable input to monitor signals * Silent operation by removal of unwanted calls * Selectable voice companding * Voice processing facilities, including Tx and Rx gain setting and voice/subaudio filtering * C-BUS serial host interface * RF interface allowing 1 or 2 point modulation * Programmable soft limiter * Enhanced CTCSS and 23/24 bit DCS codecs * Zero `talk down' CTCSS decoder performance prevents dropouts * `All call code' and `monitor' modes for CTCSS * Audio scrambling * Robust Half Duplex FFSK/MSK modem, 1200/2400 bps, gets data through when signal is too degraded for voice - for text messaging/paging, location transfer, etc. applications. * XTCSS channel and data signalling * Robust automatic packet data protocol with: Error correction and detection, Interleaving and data scrambling/privacy coding. 2004 CML Microsystems Plc FRS Signalling Processor CMX882 1.1 Brief Description CMX882, a full-function half-duplex audio and signalling processor IC for FRS and PMR446 type facilities suitable for both complex and simple end-designs. Under the control of the host C, all voiceband requirements are catered for: voiceband and sub-audio filtering, pre/de-emphasis, compression and expansion and audio routing and global level setting with single or two-point modulation in the transmit path. The combination of new and standard signalling functions of this product offer, under software control, increased functionality, versatility and privacy. Standard Extended-Code CTCSS and DCS functions are integrated with the new XTCSS code implementation. XTCSS provides additional and improved squelchcentred privacy codes with the added advantage of `silent operation'; no annoying interference from other sub-audio users. XTCSS fitted radios enjoy more privacy and flexibility of operation. For advanced and enhanced radio operation, the CMX882 provides a 1200/2400 bps free-format and packet data FFSK/MSK modem for text messaging/paging, passing GPS location data (compatible with NMEA 0183) and other data applications. With ultra low power requirements and graduated powersave, this product only requires a smaller, lowerpower C than existing FRS/PMR446 solutions. It is available in compact SSOP and TSSOP packages. 2004 CML Microsystems Plc 2 D/882/7 FRS Signalling Processor CMX882 CMX882 Functions and Facilities Half Duplex Operation Working in a half duplex mode, when the product is in Tx the Rx sections can be powered down to extend battery life, conversely in Rx major sections of the Tx can be treated in the same manner. Serial Control and Data Interfaces C-BUS: Serial control, data and command program interface compatible with SCI, SPI and Microwire type interfaces. Power Requirements and Economy With an ultra low power requirement, the CMX882 operates from a single 2.7 to 3.6 Volt supply with graduated `Sleep Mode' powersaving facilities for both Rx and Tx modes. 2004 CML Microsystems Plc 3 D/882/7 FRS Signalling Processor CMX882 Signalling: XTCSS A state-of-the-art (squelch) signalling format, employing both sub-audio (CTCSS) and in-band (XTC) signalling concurrently, which offers more than twice as many privacy codes as standard CTCSS operation and completely eliminates interference caused by other traffic on the channel (quiet operation). Additionally the XTCSS signalling can be employed as an over-air control for such features as voicecompression. XTCSS is fully compatible with both conventional and enhanced CTCSS signalling operations and will implement the All Call Code function. CTCSS 'Zero talkdown' performance eliminates unwanted breaks in communication. The CMX882 is preprogrammed with 39 standard CTCSS (+ Notone and DCS `turn off' tone) and 12 additional `split-tone' frequencies. Any one of these can be selected for reception or transmission. Decoding is aided by the use of adjustable decode bandwidths and threshold levels. Decoding is carried out rapidly thus avoiding the loss of the beginning of speech or data signals. A CTCSS configuration of this product enables `Tone Cloning'. Two unique features of this product are its CTCSS `All Call Code' and `All Codes Monitor' modes: All Call Code - transmissions using this code will be heard by all CMX882 enhanced radios regardless of their selected CTCSS code. This provides an important benefit to both safety and convenience. All Codes Monitor - selection of this code at the receiver enables all transmissions that are using a CTCSS tone to be heard, and the tone number to be reported. Open channel noise or calls lacking coding, will go unheard. This is a superior method of `channel monitoring', which allows miscoded calls from conventional CTCSS-party radios to be heard and directly responded to. 2004 CML Microsystems Plc 4 D/882/7 FRS Signalling Processor CMX882 DCS The DCS code is in NRZ format and is transmitted at 134.4b/s in either 23 or 24 bit patterns. The code, for transmission or reception is programmed via the host C with the `turn off' tone being supplied from the CTCSS facility. Decoding is carried out rapidly thus avoiding the loss of the beginning of speech or data signals. FFSK/MSK Modem This high performance modem facilitates data transfers (e.g. text messaging/paging caller identification, caller location, digital poll of remote radio location, GPS information, etc.) by providing a 1200/2400 bps MSK data packet encoder (suitable for NMEA 0183 data transfer). Software selectable interleaving, error correction (FEC), error checking (CRC) and data scrambling functions provide multiple communication types to select from robustness, speed and privacy options. In the Rx path, a 1200/2400 bps data packet decoder features automatic bit-rate recognition, 16-bit frame-sync detector, error correction and checking, data de-scrambling and packet disassembly. High performance allows the modem to be used even when radio link quality is too degraded for voice communications. Modulation type is optimised to maximise robustness and data rate and simplify hardware connections to voice radio Tx and Rx circuits with virtually no modification. The modulation type also is appropriate to develop F2D type emissions, as required by certain regulations. (F2D = frequency modulation, digital modulation with modulated subcarrier, transmitted information is data/telemetry/telecommand). Signal Monitor An auxiliary circuit intended for the monitoring of any signal or level; both internal and external. This function can be used in conjunction with the host C to allow such activities as: VOX operation and/or the `wake-up' of powered-down circuitry. Audio Processing: Adjustable Gain Input Amplifiers Selectable, component adjustable inputs are available for microphone or line voiceband or discriminator inputs. In either mode (Tx or Rx) the selected input can be further level adjusted under the control of the host C prior to signal or audio- processing. Voiceband and Sub-Audio Filtering with Limiting Both Rx and Tx paths present voiceband filtering; the Tx path filter can be configured to either 12.5 or 25 kHz channel spacing whilst the Rx path also includes a sub-audio passband filter. Voiceband Pre-emphasis and De-emphasis Voiceband pre-emphasis is selectable to either 12.5 or 25 kHz channel configurations in the Tx path; deemphasis at -6dB/ octave is selectable in the Rx path. Software Adjustable Gains, Volume, Mixing and Routing Providing total flexibility of operation, this product, under C control has the ability to select and route functions and audio and signal paths, set bandwidths and threshold levels, mix audio and sub bands and vary both input and out gain/attenuation levels. Output levels from all analogue ports can be `ramped' up and down at independently programmed rates. Attenuation-Adjustable Single/Two-Point Modulation Outputs To facilitate a wide range of transmitter types, the CMX882 has the ability to provide, independently programmable, modulation outputs; for single or two-point modulation schemes. Scrambler An optional frequency inversion scrambler is provided in both transmit and receive modes. 2004 CML Microsystems Plc 5 D/882/7 FRS Signalling Processor CMX882 CONTENTS Section 1.0 1.1 1.2 1.3 1.4 Page Features........................................................................................................................2 Brief Description............................................................................................................2 Block Diagram...............................................................................................................8 Signal List .....................................................................................................................9 External Components .................................................................................................. 11 1.4.1 PCB Layout Guidelines and Power Supply Decoupling ................................... 12 1.4.2 Modulator Outputs .......................................................................................... 13 General Description..................................................................................................... 14 1.5.1 Sleep Mode and Auto Start Up........................................................................ 16 1.5.2 Auxiliary ADC ................................................................................................. 16 1.5.3 Receive Mode................................................................................................. 17 1.5.4 Transmit Mode................................................................................................ 25 1.5.5 FFSK/MSK Data Packeting............................................................................. 29 1.5.6 XTCSS Coding................................................................................................ 32 1.5.7 C-BUS Operation ............................................................................................ 34 C-BUS Register Description ........................................................................................ 35 Application Notes ........................................................................................................ 57 1.7.1 CRC and FEC encoding information ............................................................... 57 1.7.2 Data Interleaving............................................................................................. 58 1.7.3 Scrambler Seed Transfer ................................................................................ 58 Performance Specification........................................................................................... 59 1.8.1 Electrical Performance.................................................................................... 59 1.8.2 Packaging....................................................................................................... 69 Page 1.5 1.6 1.7 1.8 Table Table 1 Voice Processing Combinations ................................................................................... 15 Table 2 Concurrent Rx Signalling Modes Supported by the CMX882 ....................................... 17 Table 3 CTCSS Tones ............................................................................................................. 20 Table 4 DCS Modulation Modes............................................................................................... 21 Table 5 DCS 23 Bit Codes ....................................................................................................... 22 Table 6 In-band Tones ............................................................................................................. 23 Table 7 Concurrent Tx Modes Supported by the CMX882 ........................................................ 25 Table 8 Data Frequencies for each Baud Rate ......................................................................... 29 Table 9 Maximum Data Transfer Latency................................................................................. 32 Figure Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Page Block Diagram ............................................................................................................. 8 Recommended External Components ........................................................................ 11 Power Supply Connections and De-coupling .............................................................. 12 Modulator output components to achieve -100dB/decade roll-off................................ 13 Rx Audio Filter Frequency Response ......................................................................... 18 De-emphasis Curve for TIA/EIA-603 Compliance....................................................... 18 Low Pass Sub-Audio Band Filter for CTCSS and DCS ............................................... 19 2004 CML Microsystems Plc 6 D/882/7 FRS Signalling Processor CMX882 Figure 8 25kHz Channel Audio Filter Response Template........................................................ 26 Figure 9 12.5kHz Channel Audio Filter Response Template..................................................... 26 Figure 10 Audio Frequency Pre-emphasis Template ................................................................ 27 Figure 11 Modulating Waveforms for 1200 and 2400 Baud FFSK/MSK Signals....................... 28 Figure 12 C-BUS Transactions................................................................................................. 34 Figure 13 Possible FRS + GPS Configuration .......................................................................... 57 Figure 14 C-BUS Timing.......................................................................................................... 67 Figure 15 Typical FFSK/MSK Bit Error Rate Graph.................................................................. 68 Figure 16 Mechanical Outline of 28-pin SSOP (D6): Order as part no. CMX882D6 ................ 69 Figure 17 Mechanical Outline of 28-pin TSSOP (E1): Order as part no. CMX882E1 .............. 69 It is always recommended that you check for the latest product datasheet version from the Datasheets page of the CML website: [www.cmlmicro.com]. 2004 CML Microsystems Plc 7 D/882/7 FRS Signalling Processor CMX882 1.2 Block Diagram Figure 1 Block Diagram 2004 CML Microsystems Plc 8 D/882/7 FRS Signalling Processor CMX882 1.3 Signal List Signal Name VDD(D) Type Power The digital positive supply rail. This pin should be decoupled to VSS(D) by a capacitor mounted close to the device pins. The negative supply rail (digital ground). The analogue positive supply rail. Levels and thresholds within the device are proportional to this voltage. This pin should be decoupled to VSS(A) by a capacitor mounted close to the device pins. The negative supply rail. Both pins must be connected to analogue ground. No connection should be made to these pins. A 'wire-ORable' output for connection to the Interrupt Request input of the host. This output is pulled down to VSS(D) when active and is high impedance when inactive. An external pull-up resistor is required. The C-BUS serial data output to the host. This output is held at high impedance when not sending data to the host. The C-BUS serial clock input from the host. The C-BUS serial data input from the host. The C-BUS data loading control function. Data transfer sequences are initiated, and completed by the CSN signal. Description Package D6, E1 Pin No. 23 5 18 VSS(D) VDD(A) Power Power 9, 21 1, 2 3 VSS(A) Power NC IRQN O/P 4 6 7 8 REPLY_DATA SERIAL_CLOCK CMD_DATA CSN T/S I/P I/P I/P 2004 CML Microsystems Plc 9 D/882/7 FRS Signalling Processor CMX882 1.3 Signal List (continued) Signal Name VBIAS Type O/P Internally generated bias voltage of approximately VDD(A)/2, except when bias is power-saved when VBIAS will discharge to VSS(A). This pin should be decoupled to VSS(A) by a capacitor mounted close to the device pins. Input terminal of discriminator input amplifier. Output / feedback terminal of discriminator input amplifier. Input terminal of amplifier 2, for either a second microphone or discriminator input. Output / feedback terminal of input amplifier 2. Input terminal of microphone input amplifier. Output / feedback terminal of microphone input amplifier. Signal Monitor input to the internal level detecting circuit. Modulator 1 output. Modulator 2 output. Output of the audio section. The input to the on-chip oscillator for an external crystal or a clock circuit. Buffered (un-inverted) clock output available for use by other devices in the system. Test input, connect to VSS(D). No connection should be made to these pins. Description Package D6, E1 Pin No. 10 11 12 13 14 15 16 17 19 20 22 24 25 26 27, 28 DISC DISC_FB INPUT_2 INPUT_2_FB MIC MIC_FB SIG_MONITOR MOD_1 MOD_2 AUDIO CLOCK/XTAL CLOCK_OUT I/P O/P I/P O/P I/P O/P I/P O/P O/P O/P I/P O/P I/P NC Notes: I/P O/P T/S NC = = = = Input Output 3-state Output No Connection 2004 CML Microsystems Plc 10 D/882/7 FRS Signalling Processor CMX882 1.4 External Components VDD(D) R1 NC NC IRQN REPLY_DATA 1 2 3 4 5 6 7 8 9 10 11 12 13 14 C6 28 27 26 25 24 NC NC VSS(D) CLOCK_OUT CLOCK/XTAL VDD(D) AUDIO VSS(A) MOD_2 MOD_1 VDD(A) SIG_MONITOR MIC_FB MIC C7 R7 R8 C9* D1* R9* R10* C10* VSS(A) R3 R4 C1 C3 Modulator reference Modulator control C4 R2 C2 Loudspeaker amp VSS(D) X1 C-BUS Interface VSS(D) SERIAL_CLOCK CMD_DATA CMX882 23 22 21 20 19 18 17 16 15 Discriminator C8 C5 CSN VSS(A) R5 VBIAS DISC DISC_FB R6 INPUT_2 INPUT_2_FB Microphone VSS(A) Figure 2 Recommended External Components R1 R2 R3 R4 R5 R6 R7 R8 100k 100k 100k 100k See note 2 100k See note 3 100k R9 R10 C1 C2 C3 C4 C5 See note 6 See note 6 100pF 1nF 100pF 100pF 100pF C6 C7 C8 C9/10 X1 D1 See note 4 200pF See note 4 See note 6 18.432MHz See note 6 See note 1 Resistors 5%, capacitors and inductors 20% unless otherwise stated. Notes: 1. X1 can be a crystal or an external clock generator; this will depend on the application. The clock drift requirement is defined in section 1.8.1. The tracks between the crystal and pin 24 and pin 5 should be as short as possible to achieve maximum stability and best start up performance. 2. R5 should be selected to provide the desired dc gain (assuming C8 is not present) of the discriminator input, as follows: GAINDisc = 100k / R5 The gain should be such that the resultant output at the DISC_FB pin is within the discriminator input signal range specified in section 1.8.1. 3. R7 should be selected to provide the desired dc gain (assuming C6 is not present) of the microphone input as follows: GAINMic = 100k / R7 The gain should be such that the resultant output at the MIC_FB pin is within the microphone input signal range specified in section 1.8.1. C6 and C8 should be selected to maintain the lower frequency roll-off of the microphone and discriminator inputs as follows: C6 = 30nF x GAINMic C8 = 100nF x GAINDisc and C6 > 1000F / R7 and C8 > TBAF / R5 4. 2004 CML Microsystems Plc 11 D/882/7 FRS Signalling Processor CMX882 5. INPUT_2 and INPUT_2_FB connections allow the user to have a second discriminator or microphone input. Component connections and values are as for the networks around pins 11 and 12 or pins 15 and 16 respectively. If this input is not required pin 13 must be connected to pin 14. The circuit formed by D1, C9, C10, R9 and R10 is a peak detector, this is only required when the signal monitor is connected to an ac signal (e.g. microphone or received signal). For a dc type signal (e.g. RSSI) these components are not required. The values of C9 and R10 set the attack time, C9 and R9 set the decay time. D1 can be any suitable small signal diode. R10 should be a high enough value so as not to distort the signal source. PCB Layout Guidelines and Power Supply Decoupling Digital Ground 1 2 3 4 VSS(D) 5 6 provision for wire link VSS(A) VBIAS C15 7 8 9 10 11 12 13 14 28 27 26 25 24 L1 VDD(D) Digital +ve Supply C11 C12 Digital ground plane 6. 1.4.1 + Clock Output CM X882 23 22 21 20 19 18 17 16 15 VSS(A) C13 C14 Analogue Ground + VDD(A) L2 Analogue +ve Supply Analogue ground plane Figure 3 Power Supply Connections and De-coupling C11 C12 C13 10nF 10F 10nF C14 C15 10F 100nF L1 L2 100nH 100nH See note 7 See note 7 Resistors 5%, capacitors and inductors 20% unless otherwise stated. Notes: 7. The inductors L1 and L2 can be omitted but this may degrade system performance. It is important to protect the analogue pins from extraneous inband noise and to minimise the impedance between the CMX882 and the supply and bias de-coupling capacitors. The de-coupling capacitors C11, C12, C13 and C14 should be as close as possible to the CMX882, particularly C11 and C13. It is therefore recommended that the printed circuit board is laid out with separate ground planes for the VSS(A) and VSS(D) in the area of the CMX882, with provision to make a link between them close to the CMX882. VBIAS is used as an internal reference for detecting and generating the various analogue signals. It must be carefully decoupled, to ensure its integrity, so apart from the decoupling capacitor shown, no other loads should be connected. If VBIAS needs to be used to set the discriminator mid-point reference, it must be buffered with a high input impedance buffer. The single ended microphone input(s) and audio output must be ac coupled as shown, so their return paths can be connected to VSS(A) without introducing dc offsets. Further buffering of the audio output is advised. The crystal X1 can be replaced with an external clock source if required/desired. The internal clock generating circuit can be placed in power-save mode if the clock is provided externally. 2004 CML Microsystems Plc 12 D/882/7 FRS Signalling Processor CMX882 1.4.2 Modulator Outputs The combination of CMX882 and the modulator output components, R3/C3 and R4/C4, achieve roll-off rates better than -60dB/decade. If required this can be increased to better than -100dB/decade by replacing R3/C3 and R4/C4 with the active filter circuit shown in Figure 4. C17/C19 MOD_1/2 + R11/R13 R12/R14 C16/C18 VSS(A) Modulator 1 & 2 Figure 4 Modulator output components to achieve -100dB/decade roll-off R11 R12 R13 R14 120k 120k 120k 120k C16 C17 C18 C19 220pF 440pF 220pF 440pF (2 x C16) (2 x C18) Resistors 5%, capacitors and inductors 20% unless otherwise stated. Notes: 8. The external op-amp must be chosen to ensure that the required signal output level can be driven within acceptable distortion limits. 2004 CML Microsystems Plc 13 D/882/7 FRS Signalling Processor CMX882 1.5 General Description The CMX882 is intended for use in half duplex analogue two way land mobile radio (LMR) equipment and is particularly suited to enhanced MURS / GMRS / FRS with GPS terminal designs. The CMX882 provides radio signal encoder and decoder functions for: Voice, in-band tones, XTCSS, CTCSS, DCS and FFSK/MSK data permitting simple to sophisticated levels of tone control and data transfer. Power control facilities allow the device to be placed in varying levels of sleep allowing the user to fine tune the power depending on system requirements. The CMX882 includes a crystal clock generator, with buffered output, to provide a common system clock if required. A block diagram of the CMX882 is shown in Figure 1. Tx functions Audio o Single/dual microphone inputs with input amplifier and programmable gain adjustment o Filtering selectable for 12.5kHz and 25kHz channels o Selectable pre-emphasis o Selectable compression o Selectable frequency inversion voice scrambling o 2-point modulation outputs with programmable level adjustment Signalling o Pre-programmed 51 tone CTCSS encoder o Programmable 23/24bit DCS encoder o Programmable audio tone generator (for custom audio tones) o Pre-programmed XTCSS and in-band tone encoder o 1200/2400bps MSK data packet encoder (suitable for text messaging/paging, caller identification, caller location, digital poll of remote radio location, GPS information via NMEA 0183 data transfer etc.), incorporating interleaving, FEC, CRC and data scrambler Rx functions Audio o Single/dual demodulator inputs with input amplifier and programmable gain adjustment o Voice-band and sub-audio rejection filtering o Selectable de-emphasis o Selectable expansion o Selectable frequency inversion voice de-scrambling o Software volume control Signalling o 1 from 51 CTCSS decoder + Tone Clone mode o 23/24bit DCS decoder o Pre-programmed in-band tone decode with XTCSS 4 tone addressing o 1200/2400bps MSK data packet decoder with automatic bit rate recognition, 16 bit frame sync detector, error correction, data de-scrambler and packet disassembly o Signal Monitor (RSSI / Microphone / Rx channel level monitor) 2004 CML Microsystems Plc 14 D/882/7 FRS Signalling Processor CMX882 Voice Processing Combinations Table 1 shows the valid voice processing combinations. Table 1 Voice Processing Combinations TX Compress Scramble Pre-Emphasis Filter Filter De-Emphasis RX De-Scramble Expand 1 2 3 4 5 6 Not Valid 7 Not Recommended 81 Host Interface A serial data interface (C-BUS) is used for command, status and data transfers between the CMX882 and the host C; this interface is compatible with microwire, SPI etc. Interrupt signals notify the host C when a change in status has occurred and the C should read the status register across the C-BUS and respond accordingly. Interrupts only occur if the appropriate mask bit has been set. See section 1.6.15. Auxiliary (Signal Monitor) analogue signal The CMX882 includes a Signal level monitor. This is an 8-bit successive approximation ADC and a two level signal sensor. The two level sensor facility can be used in conjunction with the power saving mode to wake up powered down blocks, and issue an interrupt on the IRQN line when the Signal exceeds the preset threshold level. The auxiliary ADC voltage reference is taken directly from the VDD(A) supply, so the Signal level being monitored should be derived from this supply voltage. 1 Audio quality is somewhat degraded. 2004 CML Microsystems Plc 15 D/882/7 FRS Signalling Processor CMX882 1.5.1 Sleep Mode and Auto Start Up Power-on reset or C-BUS general reset places the CMX882 into sleep mode, which results in all internal blocks, except the xtal clock circuit, being placed in power-saved mode. The xtal clock circuit can be power-saved but this must be done by an explicit C-BUS command. Power saving is achieved by turning off bias current sources or disabling local clocks, as appropriate. During system standby periods, parts of the device can be put into sleep mode by the host to conserve power. The Auxiliary ADC can be programmed so that when the level exceeds a threshold, an interrupt is issued over the C-BUS and the selected mode (Tx or Rx) "woken up" within 400s. If this time is too long to ensure no part of the signal is lost, the DISC or MIC input and ADC path can be kept powered up whilst in standby mode. The receive modes and transmit modes can also be activated by commands from the C-BUS. On wake up, activation of the various signal path stages are phased appropriately to avoid causing unwanted transients. More details are provided in section 1.6.4 on Signal Routing. The CMX882 can be programmed to wake up its receive path automatically (automatic start-up) when the DISC input level exceeds the `high' level threshold. While the CMX882 is in automatic receive start-up mode the DISC input must also be selected for the signal path. When not in automatic start-up mode it is recommended that the required input is selected during Auxiliary ADC operation to avoid subsequent switching of the input signal source. 1.5.2 Auxiliary ADC This section of the CMX882 operates in both Tx and Rx modes and can be used to monitor one of 4 signal sources: Sig_Monitor pin, MIC1, Input_2 or DISC inputs. Activity on the selected input will optionally issue an interrupt if host intervention is required. During idle periods the majority of the CMX882 can be placed into low power mode. If monitoring ac signals connected to the Sig_Monitor pin they must be rectified and filtered using passive external circuitry. The Auxiliary ADC facility comprises an 8-bit ADC, a comparator, an 8-bit result data word and two 8-bit threshold registers, one defining the `Signal high' level and the other the `Signal low' level. The two threshold registers are combined into one 16-bit C-BUS register word. The ADC measures the Signal level at intervals that are set by C-BUS command. It is advised that the interval be set to <125s while waiting for a new incoming signal so that the CMX882 and host C can be powered up and put into the correct mode in time to avoid missing any part of the signal. The default interval period following a reset is 20.8s. Power dissipation of the Auxiliary ADC can be reduced by increasing the conversion interval time. The result of the most recent Auxiliary ADC measurement can be read over the C-BUS whenever the Signal Processing and Aux ADC circuits are powered up. The Auxiliary ADC compares each conversion result with the values in the `Signal high' or the `Signal low' threshold registers. The CMX882 can, for example, issue an interrupt to the host C to wake up the receive path when the Auxiliary ADC input exceeds the `high' level threshold. The CMX882 can also issue an interrupt to the host C to indicate a weak or absent signal when it falls below the `low' level threshold. This provides a user programmable hysteresis facility. The host must ensure that the value in the `low' register is always less than that of the `high' register. The options for issuing interrupts and for automatic start-up are selected by C-BUS command. The Auxiliary ADC options are controlled by the $B2, $B3 and $C0 C-BUS registers. The Auxiliary ADC requires the Auxiliary ADC, BIAS and Xtal clock to all be enabled in the Power Down Control register. 2004 CML Microsystems Plc 16 D/882/7 FRS Signalling Processor CMX882 1.5.3 Receive Mode The CMX882 can receive voice and various signal formats: CTCSS tone, DCS code, XTCSS / In-band tones and FFSK/MSK data at 1200 and 2400bps. Reception of each of these signal types can be independently enabled/disabled by C-BUS command. If enabled, an interrupt will be issued to notify the host C of the presence and type of the incoming signal. In receive mode the CMX882 performs signal type identification in 2 frequency bands, sub-audio (60 260Hz) and voice band (300 - 3kHz), to determine what type of signal is being received. When an enabled signal is detected this will be indicated to the host over the C-BUS and the CMX882 will continue to process the received signal in its band. Identification / process mode will continue in the other band. The CMX882 can process voice and simultaneously identify and process at least 2 other signal types (one in the sub-audio in parallel with one in the voice band). See Table 2 for valid combinations. These combinations can be used with Voice Processing, if desired. The receive gain and audio output amplifier gain can be adjusted by the host C, via C-BUS command, to provide receive signal level adjustment and output volume control or muting. Table 2 Concurrent Rx Signalling Modes Supported by the CMX882 Sub-Audio All combinations of: With Rx Voice 1 Processing or Audio Tone generation DCS Inverted DCS CTCSS Sub-Audio All combinations of: DCS Inverted DCS CTCSS Voice band signalling Any one of A - E: A None B 1200bps FFSK/MSK C 2400bps FFSK/MSK D 1200 & 2400 bps FFSK/MSK 3 E XTCSS Voice band signalling One of A, B or E: None 1200bps FFSK/MSK 3 XTCSS With Rx Voice 2 Processing A B E Sub-Audio All combinations of: No Voice Processing or Audio Tone generation DCS Inverted DCS CTCSS Voice band signalling All combinations of: XTCSS 1200bps FFSK/MSK 2400bps FFSK/MSK 3 1 Including optional de-emphasis and companding, but excluding voice scrambling 2 Including voice scrambling 3 XTCSS or In-band tone signalling By disabling all the decoding modes, the device can be configured to receive voice only signals with no decoding of the voice band, CTCSS or DCS signalling. This will result in reception of all signals as if they are voice. In this case it is up to the user/host C to respond appropriately to incoming signals. The CMX882 operates in half duplex, so whilst in receive mode the transmit path (microphone input and modulator output amplifiers) can be disabled and powered down if required. The AUDIO output signal level is equalised (to VBIAS) before switching between the audio port and the modulator ports, to minimise unwanted audible transients. The Off/Power-save level of the modulator outputs is the same as the VBIAS pin, so the audio output level must also be at this level before switching. 2004 CML Microsystems Plc 17 D/882/7 FRS Signalling Processor CMX882 1.5.3.1 Receiving Voice Band Signals When a voice based signal is being received, it is up to the C, in response to signal status information provided by the CMX882, to control muting/enabling of the voice band signal to the AUDIO output. The discriminator path through the device has a programmable gain stage. Whilst in receive mode this should normally be set to 0dB (the default) gain. Receive Filtering The incoming signal is filtered, as shown in Figure 5, to remove sub-audio components and to minimise high frequency noise. When appropriate the voice signal can then be routed to the AUDIO output. 10 250Hz 0 -10 Filter response -20 -30 -40 300Hz -50 -60 10Hz 100Hz 1000Hz Frequency (Hz) 10000Hz 100000Hz 3kHz Template Figure 5 Rx Audio Filter Frequency Response De-emphasis Optional de-emphasis at -6dB per octave from 300Hz to 3000Hz (shown in Figure 6) can be selected to facilitate compliance with TIA/EIA-603. 16 12 8 4 dB 0 -4 -8 -3dB +1dB 0dB 0dB/octave -6dB/octave -12 -16 -20 2500 250 100 1000 Frequency (Hz) 10000 -18dB/octave Figure 6 De-emphasis Curve for TIA/EIA-603 Compliance 2004 CML Microsystems Plc 18 D/882/7 FRS Signalling Processor CMX882 Rx Companding (Expanding) The CMX882 incorporates an optional syllabic compandor in both transmit and receive modes. This expands received voice band signals that have been similarly compressed in the transmitter to enhance dynamic range. The compandor attack, decay and 0dB point are defined in section 1.8.1. See section 1.6.9 for details of how to control this function. Audio De-Scrambling The CMX882 incorporates an optional frequency inversion de-scrambler in receive mode. This descrambles received voice band signals that have been scrambled in the transmitter. See section 1.6.9 for details of how to control this function. Voice Processing Combinations Table 1 shows the valid voice processing combinations. (See section 1.5). 1.5.3.2 Receiving and Decoding CTCSS Tones The CMX882 is able to accurately detect valid CTCSS tones quickly to avoid losing the beginning of voice or possibly data transmissions, and is able to continuously monitor the detected tone with minimal probability of falsely dropping out. The received signal is filtered in accordance with the template shown in Figure 7, to prevent signals outside the sub-audio range from interfering with the sub-audio tone 10 0 -10 Gain (dB) -20 -30 -40 -50 -60 -70 0 200 400 600 800 1000 Frequency (Hz) detection. Figure 7 Low Pass Sub-Audio Band Filter for CTCSS and DCS Once a valid CTCSS tone has been detected, the voice band signal can be passed to the audio output. The voice band signal is extracted from the received signal by band pass filtering as shown in Figure 5. To help decode received CTCSS tones adjustable decoder bandwidths and threshold levels permit decode certainty and signal to noise performance to be traded when congestion or range limits the system performance. This entails setting the tone decoder bandwidth and threshold level in P2.1 of the Programming register ($C8) and programming the Audio & Tx CTCSS Control register with the desired tone. Tone Cloning: TM Tone Cloning facilitates the detection of CTCSS tones 1 to 39 in receive mode. This allows the device to non-predictively detect any tone in this range. The received tone number will be reported in the Tones Status register. This tone code can then be programmed into the `Audio and Device Address Control' register, by the host C. The cloned tone will only be active when CTCSS is enabled in the Mode register. Tone Cloning is a trademark of CML Microsystems Plc. 2004 CML Microsystems Plc 19 D/882/7 FRS Signalling Processor CMX882 Tone cloning should not be used in systems where tones 41 to 51 or other split tones (tones between the frequencies of tones 1 to 40) may be received. The all call tone 40 can still be used after tone cloning has been performed. CTCSS Tones Table 3 lists the CTCSS tones available. The tone numbers are decimal equivalents of the numbers written to the Audio & Device Address Control register ($C2) and reported in the Tone Status register ($CC). Table 3 CTCSS Tones Tone Freq. Tone Freq. Tone Freq. Number (Hz) Number (Hz) Number (Hz) 1 2 00 No Tone 20 131.8 40 62.5* 01 67.0 21 136.5 41 159.8* 02 71.9 22 141.3 42 165.5* 03 74.4 23 146.2 43 171.3* 04 77.0 24 151.4 44 177.3* 05 79.7 25 156.7 45 183.5* 06 82.5 26 162.2 46 189.9* 07 85.4 27 167.9 47 196.6* 08 88.5 28 173.8 48 199.5* 09 91.5 29 179.9 49 206.5* 10 94.8 30 186.2 50 229.1* 11 97.4 31 192.8 51 254.1* 12 100.0 32 203.5 52-54 Reserved 13 103.5 33 210.7 553 Invalid 14 107.2 34 218.1 tone 15 110.9 35 225.7 >=56 Reserved 16 114.8 36 233.6 17 118.8 37 241.8 18 123.0 38 250.3 19 127.3 39 69.3 * Subaudio tone not in TIA-603A standard. Notes: 1 Tone number 00 in the Tone Status register ($CC) indicates that none of the above subaudio tones is being detected - see also section 1.6.19. If tone number 00 is programmed into the Audio & Device Address Control register ($C2) only tone 40 will be scanned for - see note 2. If CTCSS transmit is selected this tone setting will cause the CTCSS generator to output no signal. Tone number 40 provides an all user CTCSS tone option; regardless of the subaudio tones set, the CMX882 will indicate to the host when this tone is detected whenever the CTCSS detector is enabled. This feature is useful for implementing emergency type calls e.g. all call. Tone number 55 is reported in the Tone Status register ($CC), when CTCSS receive is enabled and a subaudio tone is detected that does not correspond to the selected tone or the all-call tone (tone number 40). This could be a tone in the subaudio band which is not in the table or a tone in the table which is not the selected tone or all-call tone. 2 3 2004 CML Microsystems Plc 20 D/882/7 FRS Signalling Processor CMX882 1.5.3.3 Receiving and Decoding DCS Codes DCS Code is in NRZ format and transmitted at 134.4 0.4bps. The CMX882 is able to decode any 23 or 24 bit pattern in either of the two DCS modulation modes defined by TIA/EIA-603 and described in Table 4. The CMX882 can detect a valid DCS Code quickly enough to avoid losing the beginning of voice transmissions. Modulation Type: A B Table 4 DCS Modulation Modes Data Bit: FM Frequency Change: 0 Minus frequency shift 1 Plus frequency shift 0 Plus frequency shift 1 Minus frequency shift The CMX882 detects the DCS code that matches the programmed code defined in the `DCS Code' words (P2.2-3) in the Programming register ($C8). To detect the pre-programmed DCS code the signal is low pass filtered to suppress all but the sub-audio band using the filter shown in Figure 7. Further equalisation filtering, signal slicing and level detection are done to extract the code being received. The extracted code is then matched with the programmed 23 or 24-bit DCS code to be recognised, in the order least significant first through to most significant DCS code bit last. Table 5 shows a selection of valid 23-bit DCS codes, this does not preclude other codes being programmed. Recognition of a valid DCS Code will be flagged if the decode is successful (3 or less errors). A failure to decode is indicated by a '0' flag. This flag is updated after the decoding of every 4th bit of the incoming signal. Once a valid DCS Code has been detected, the voice band signal can be passed to the AUDIO output under the control of the host C. The voice signal is extracted from the received input signal by band pass filtering; see Figure 5. More details for programming DCS Codes are provided in section 1.6.20.3. The end of DCS transmissions is indicated by a 134.4 0.5Hz tone for 150-200ms. To detect the DCS turn off tone while receiving DCS, the DCS turn off tone option must be selected in the Audio and CTCSS Control ($C2) register and CTCSS receive must also be enabled. When a DCS turn off tone is detected it will cause a DCS interrupt; the receiver audio output can then be muted by the host. 2004 CML Microsystems Plc 21 D/882/7 FRS Signalling Processor CMX882 Table 5 DCS 23 Bit Codes DCS Code 023 025 026 031 032 043 047 051 054 065 071 072 073 074 114 115 116 125 131 132 134 143 152 155 156 162 165 172 DCS bits 22-12 763 6B7 65D 51F 5F5 5B6 0FD 7CA 6F4 5D1 679 693 2E6 747 35E 72B 7C1 07B 3D3 339 2ED 37A 1EC 44D 4A7 6BC 31D 05F DCS bits 11-0 813 815 816 819 81A 823 827 829 82C 835 839 83A 83B 83C 84C 84D 84E 855 859 85A 85C 863 86A 86D 86E 872 875 87A DCS Code 174 205 223 226 243 244 245 251 261 263 265 271 306 311 315 331 343 346 351 364 365 371 411 412 413 423 431 432 DCS bits 22-12 18B 6E9 68E 7B0 45B 1FA 58F 627 177 5E8 43C 794 0CF 38D 6C6 23E 297 3A9 0EB 685 2F0 158 776 79C 3E9 4B9 6C5 62F DCS bits 11-0 87C 885 893 896 8A3 8A4 8A5 8A9 8B1 8B3 8B5 8B9 8C6 8C9 8CD 8D9 8E3 8E6 8E9 8F4 8F5 8F9 909 90A 90B 913 919 91A DCS Code 445 464 465 466 503 506 516 532 546 565 606 612 624 627 631 632 654 662 664 703 712 723 731 732 734 743 754 DCS bits 22-12 7B8 27E 60B 6E1 3C6 2F8 41B 0E3 19E 0C7 5D9 671 0F5 01F 728 7C2 4C3 247 393 22B 0BD 398 1E4 10E 0DA 14D 20F DCS bits 11-0 925 934 935 936 943 946 94E 95A 966 975 986 98A 994 997 999 99A 9AC 9B2 9B4 9C3 9CA 9D3 9D9 9DA 9DC 9E3 9EC 1.5.3.4 Receiving and Decoding In-band Tones In-band tones can be used to flag the start of a call or to confirm the end of a call. If they occur during a call the tone may be audible at the receiver. When enabled, an interrupt will be issued when a signal matching a valid In-band tone is detected and when a present In-band tone turns off or changes (i.e. at the start and at the end of each In-band tone). The CMX882 implements QTC coding using the EEA tone set. Other addressing and data formats can be implemented but will require more host intervention. The custom tones (1-4) permit other audio tones to be encoded or decoded, the frequency of each tone is defined in the program registers P1.2-5. In receive the CMX882 scans through the tone table sequentially, the code reported will be the first one that matches the incoming frequency. Adjustable decoder bandwidths, threshold levels are programmable via the Programming register and permits certainty of detection and signal to noise performance to be traded when congestion or range limits the system performance. The In-band signal is derived from the received input signal after the band pass filtering shown in Figure 5. 2004 CML Microsystems Plc 22 D/882/7 FRS Signalling Processor CMX882 Table 6 In-band Tones Special / Information Tones (5th bit = 0) 4 bit Code Freq. Dec Hex (Hz) 0 0 No Tone 1 1 1 Custom Tone 0 P1.2 1 2 2 Custom Tone 1 P1.3 1 3 3 Custom Tone 2 P1.4 1 4 4 Custom Tone 3 P1.5 5 5 6 6 7 7 8 8 9 9 Reserved 10 A 11 B 12 C 13 D 14 E 15 F Notes: 1 2 Normal Tones (5th bit = 1) 4 bit Code Freq. Dec Hex (Hz) 0 0 1981 1 1 1124 2 2 1197 3 3 1275 4 4 1358 5 5 1446 6 6 1540 7 7 1640 8 8 1747 9 9 1860 10 A 1055 11 B 930 12 C 2247 13 D 991 2 14 E 2110 15 F No Tone Special tones 1-4 provide user programmable tone options for both transmit and receive modes as set in the indicated Program register, for programming information see section 1.6.20.2. Normal tone 14 is the repeat tone, this code must be used in transmit when the new code to be sent is the same as the previous one. e.g. to send `333' the sequence `3R3' should be sent, where `R' is the repeat tone. When receiving Selcall tones the CMX882 will indicate the repeat tone when it is received, it is up to the host to interpret this and decode tones accordingly. 2004 CML Microsystems Plc 23 D/882/7 FRS Signalling Processor CMX882 1.5.3.5 Receiving FFSK Signals The CMX882 can decode incoming FFSK/MSK signals at either 1200 or 2400 baud data rates. It can achieve this by deriving the baud rate from the received signal. Alternatively a control word may set the baud rate, in which case the device only responds to signals operating at that rate. The form of FFSK/MSK signals for these baud rates, excluding noise, is shown in Figure 11. The received signal is filtered and data is extracted. A PLL is used to extract the clock from the recovered serial data stream. The recovered data is stored in a 2 or 4 byte buffer (grouped into 16-bit words) and an interrupt issued to indicate received data is ready. Data is transferred over the C-BUS, controlled by host instructions. If this data is not read before the next data is decoded it will be overwritten. The MSK bit clock is not output externally. It is up to the user to ensure that the data is transferred at an adequate rate following data ready being flagged, see Table 9. The extracted data is compared with the 16 bit programmed frame sync pattern. It is preset to $CB23 following a RESET command. An interrupt will be flagged when the programmed frame sync pattern is detected or when the following Frame Head is decoded, see section 1.5.5. The host may stop the frame sync search by disabling the MSK demodulator. If set to decode a Frame Head before interrupting, the CMX882 will check the CRC portion of the Frame Head Control Field. If this indicates a corrupt Frame Head a search for a new Frame Sync pattern will be automatically restarted. FFSK may be transmitted in conjunction with a CTCSS or DCS sub-audio component. The device will handle the sub-audio signals as already described. If a sub-audio signal turns off during reception of FFSK, it is up to the host C to turn off the FFSK decoding as the device will continue receiving and processing the incoming signal until commanded otherwise by the host C. The host must keep track of the message length or otherwise determine the end of reception (e.g. by using sub-audio information or the Auxiliary ADC to check for signal level) and disable the FFSK demodulator at the appropriate time. Note that when using packets with embedded size information the CMX882 will indicate when the last data block has been received. 1.5.3.6 Receiving XTCSS Signals The CMX882 can decode and monitor for XTCSS signalling. XTCSS is used to identify the start and optionally the end of voice/data/other calls. It provides additional information and control over the basic CTCSS method of channel coding. XTCSS coding starts with a 4 tone sequence indicating the address and content of the following message. Immediately after the 4 tone sequence a sub-audio maintenance tone is sent for the duration of the call. At the end of the call the maintenance tone is removed and an optional 4 tone sequence sent indicating the end of message (EOM). For further details on XTCSS see section 1.5.6. By enabling XTCSS reception the host instructs the CMX882 to search for a valid 4 tone sequence, an interrupt (if enabled) will be generated when this occurs. The 4 tone sequence will be indicated in the CBUS register ($C9) for the host to read out using the tone numbers in Table 6. The sub-audio tone will be searched for after a valid 4 tone In-band sequence if CTCSS detection is also enabled. CTCSS codes will be decoded and reported as defined in section 1.5.3.2. It is not necessary to enable CTCSS in the Mode Control register for the device to search for the XTCSS sub audio tone. In receive, whenever the XTCSS detect bit is set the CMX882 will search for a valid 4 tone In-band sequence however detection of a CTCSS tone will inhibit the search for 4 tone sequences. To be valid the 4 tones must be preceded and followed by silence in the audio band (signals below the audio detect level - see program register P1.1) for the programmed no tone time. The presence (or absence) of the sub-audio maintenance tone will only be indicated to the host if the CTCSS detect bit is also set. After the 4 tone sequence is detected the maintenance tone can be used by the host to detect fades and the end of the message and hence can disable the audio path in sympathy with this tone being absent. At any time the XTCSS enable bit is set and maintenance tone is not decoded the 4 tone set will be automatically searched for. 2004 CML Microsystems Plc 24 D/882/7 FRS Signalling Processor CMX882 It is possible (although unlikely) that a fade will exactly coincide and obliterate 2 lots of 4 tone sequence indicating an EOM and the start of a new message. In this case, the host could misinterpret the received signal as a long fade and enable the voice when the maintenance tone reappears. It is therefore recommended that the host operates a timer that is started on loss of maintenance tone. If this times out the host can then assume that the fade is long enough that the original call is lost or has become so corrupted that it is not worth continuing with. The host could then choose only to restore the audio path on the next occurrence of a valid XTCSS tone set. Note that the XTCSS detector operates independently and the host may enable or disable the audio path at any time. 1.5.4 Transmit Mode The device operates in half duplex, so when the device is in transmit mode the receive path (discriminator and audio output amplifiers) should be disabled, and can be powered down, by the host C. Two modulator outputs with independently programmable gains are provided to facilitate single or twopoint modulation, separate sub-audio and voice band outputs. If one of the modulator outputs is not used it can be disabled to conserve power. To avoid erroneous transmission of out of band frequencies when changing from Rx to Tx the MOD_1 and MOD_2 outputs are ramped to the quiescent modulator output level, VBIAS before switching. Similarly, when starting a transmission, the transmitted signal strength is ramped up from the quiescent VBIAS level and when ending a transmission the transmitted signal strength is ramped down to the quiescent VBIAS level. The ramp rates are set in the Programming register P4.6. When the modulator outputs are disabled, their outputs will be set to VBIAS. When the modulator output drivers are powered down, their outputs will be floating (high impedance), so the RF modulator will need to be turned off. Table 7 Concurrent Tx Modes Supported by the CMX882 Sub-Audio CTCSS CTCSS CTCSS CTCSS CTCCS^ DCS DCS DCS DCS + + + + + + + Voice band Voice In-band tone FFSK/MSK XTCSS Voice In-band tone FFSK/MSK Voice In-band FFSK/MSK XTCSS ^ Special subaudio tone only For all transmissions the host must only enable signals after the appropriate data and settings for those signals are loaded into the C-BUS registers. As soon as any signalling is enabled the CMX882 will use the settings to control the way information is transmitted. A programmable gain stage in the microphone input path facilitates a host controlled VOGAD capability. 2004 CML Microsystems Plc 25 D/882/7 FRS Signalling Processor CMX882 1.5.4.1 Processing Voice Signals for Transmission over Analogue Channels The microphone input(s), with programmable gain, can be selected as the voice input source. Preemphasis is selectable with either version of the 2 analogue Tx audio filters (for 12.5kHz and 25kHz channel spacing). These are designed for use in ETS-300-086 and/or TIA/EIA-603 compliant applications. Both filters attenuate sub-audio frequencies below 250Hz by more than 33dB wrt the signal level at 1kHz. These filters together with a built in limiter help ensure compliance with ETS-300-086 (25kHz and 12.5kHz channel spacing) when levels and gain settings are set up correctly in the target system. 10 0 -10 Gain (dB) -20 -30 -33dB -14dB/octave +0.5dB/-2dB wrt ref. reference 0dB at 1kHz 3kHz 250Hz -40 -50 -60 10 100 1000 Frequency (Hz) 10000 100000 Figure 8 25kHz Channel Audio Filter Response Template The filter characteristics of the 12.5kHz channel filter fits the filter template shown in Figure 9 (solid outline). This filter also facilitates implementation of systems compliant with TIA/EIA-603 `A' and `B' bands. To achieve attenuation above 3kHz of better than -100dB/decade for TIA/EIA-603 `C' bands (dashed outline), additional external circuitry is required, such as suggested in section 1.4.2. 10 0 -10 250Hz 300Hz +0.5dB/-2dB wrt ref. reference 0dB at 1kHz 3kHz -20 Gain (dB) -30 -40 -50 -60 -70 -80 -90 10 100 -33dB 300Hz -60dB/decade wrt ref. 2.55kHz (-50dB) 20kHz -100dB/decade (-82.5dB) 20kHz 1000 Frequency (Hz) 10000 100000 Figure 9 12.5kHz Channel Audio Filter Response Template 2004 CML Microsystems Plc 26 D/882/7 FRS Signalling Processor CMX882 The CMX882 provides selectable pre-emphasis filtering of +6dB per octave from 300Hz to 3000Hz, matching the template shown in Figure 10. 16 12 8 4 dB 0 -4 -8 -12 -16 -20 2500 250 100 1000 Frequency (Hz) 10000 +12dB/octave -3dB +1dB 0dB +6dB/octave Figure 10 Audio Frequency Pre-emphasis Template Modulator Output Routing The sub-audio component can be combined with the voice band signal and this composite signal routed to both MOD_1 and MOD_2 outputs, or the sub-audio and voice band signal can be output separately (sub-audio to MOD_2 and voice band to MOD_1), in accordance with the settings of the Signal Routing register ($B1). Tx Companding (Compressing) The CMX882 incorporates an optional syllabic compandor in both transmit and receive mode. This compresses voice band signals before transmission to enhance dynamic range. The compandor attack, decay and 0dB point are defined in section 1.8.1. See section 1.6.9 for details of how to control this function. Audio Scrambling The CMX882 incorporates an optional frequency inversion scrambler in transmit mode. This scrambles voice band signals to be de-scrambled in the receiver. See section 1.6.9 for details of how to control this function. Voice Processing Combinations Table 1 shows the valid voice processing combinations (see section 1.5) 1.5.4.2 CTCSS Tone The sub-audio CTCSS tone generated is defined in the Tx CTCSS register ($C2). Table 3 lists the CTCSS tones and the corresponding value for programming the TX TONE bits. 1.5.4.3 DCS Code A 23 or 24-bit sub-audio DCS Code can be generated, as defined by the `DCS Code' words (P2.4-5) of the Programming register ($C8); the same DCS Code pattern is used for detection and transmission. The DCS Code is NRZ encoded at 134.40.4 bits/s, low pass filtered and added to the voice band signal, prior to passing the signal to the modulator output stages. Valid 23-bit DCS codes and the corresponding settings for the DCS Code Register are shown in Table 5, this does not preclude other codes being programmed. The least significant bit of the DCS code is transmitted first and the most significant bit is 2004 CML Microsystems Plc 27 D/882/7 FRS Signalling Processor CMX882 transmitted last. The CMX882 is able to encode and transmit either of the two DCS modulation modes defined by TIA/EIA-603 and described in Table 4. To signal the end of the DCS transmission, the host should set the special sub-audio bits in the Audio & CTCSS Control register ($C2) to enable the DCS turn off tone for 150ms to 200ms. After this time period has elapsed the host should then disable DCS in the Mode register ($C1). Do not enable CTCSS in the Mode Control ($C1) register when transmitting the DCS turn off tone. To summarize, detection of DCS turn off tone requires the CTCSS decoder to be enabled, whereas generation of the DCS turn off tone requires the CTCSS encoder to be disabled. 1.5.4.4 Transmitting In-band Tones The In-band tone to be generated is defined in the Tx Tone register ($C3). The tone level is set in the Programming register (P1.4). The In-band tone must be transmitted without other signals in the voice band, so the host C must disable the voice path prior to initiating transmission of a In-band tone, and restore the voice path after the In-band tone transmission is complete. Table 6 shows valid In-band tones, together with the values for programming the In-band bits of the Tx Tone register. Custom In-band tone frequencies are set in the program register ($C8) P1.6-9. See section 1.6.20.2 for programming details. 1.5.4.5 Transmitting FFSK/MSK Signals The FFSK/MSK encoding operates in accordance with the bit settings in the Modem Control register ($C7). When enabled the MSK modulator will immediately begin transmitting data using the settings and values in the Tx Data and General Control register(s) and block 0 of the Programming Register. Therefore, these registers should be programmed to the required value before transmission is enabled. The CMX882 generates it's own internal data clock and converts the binary data into the appropriately phased frequencies, as shown in Figure 11 and Table 8. The binary data is taken from registers $CA and $CB, most significant bit first. The following data words must be provided over the C-BUS within certain time limits to ensure the selected baud rate is maintained. The time limits will be dependent on the data coding being used, see Table 9. Rx SIGNAL I/P 2400 BAUD LOGIC '1' LOGIC '0' LOGIC '1' LOGIC '0' Rx SIGNAL I/ P 1200 BAUD LOGIC '1' LOGIC '0' LOGIC '1' LOGIC '0' Figure 11 Modulating Waveforms for 1200 and 2400 Baud FFSK/MSK Signals 2004 CML Microsystems Plc 28 D/882/7 FRS Signalling Processor CMX882 The table below shows the combinations of frequencies and number of cycles to represent each bit of data, for both baud rates. Table 8 Data Frequencies for each Baud Rate Baud Rate 1200 baud 2400 baud Data 1 0 1 0 Frequency 1200Hz 1800Hz 1200Hz 2400Hz Number of Cycles one one and a half half one Note: FFSK may be transmitted in conjunction with a CTCSS or DCS sub-audio component. 1.5.4.6 Transmitting XTCSS Signalling XTCSS signals can be transmitted by loading the 4 tone pattern and CTCSS tone into the C-BUS registers and enabling XTCSS. The device will transmit the 4 tones in sequence, raise an interrupt when this is complete and then automatically generate the CTCSS tone (if enabled). At the end of the message the CTCSS tone can be disabled by setting the CTCSS enable bit to '0'. The XTCSS 4 tone sequence must be transmitted on its own, so if a voice or a data signal is being transmitted, this must be disabled during the XTCSS 4 tone transmission. See section 1.5.6 for more information. 1.5.5 FFSK/MSK Data Packeting The CMX882 has extensive data packeting features that can be controlled by the Modem Control register ($C7). The CMX882 can packet data in a variety of formats so the user can have the optimum data throughput for various signal to noise ratios. Data is transferred in packets or frames, each frame is made up of a Frame Head followed by any associated User Data. The Frame Head is composed of a 16 bit Bit Sync and 16 bit Frame Sync pattern immediately followed by 4 bytes of data. The 4 bytes of data start with an 8 bit address followed by 1 byte carrying information about the format of the following Data Block, a further byte indicates the size of the packet and the last byte is a checksum to detect if any of the 4 Frame Head bytes has been corrupted. 1.5.5.1 Tx Hang bit When transmitting FFSK/MSK data the user should ensure that the data is terminated with a hang bit. To do this, the host must set the 'Last Data' bit in the Modem Control Register ($C7) after the last data word has been loaded into the Tx Data register, as described in section 1.6.11. This will append a hang bit onto the end of the current word and will stop modulating after the hang bit has been transmitted. It will also generate (if enabled) an interrupt when the hang bit has left the modulator. 1.5.5.2 Frame format --------Data Block-------- Data bytes Checksum B* ---------------------------------Frame Head--------------------------------- ---Sync Field--------------------Control Field------------------ Bit Frame Address Format Size^ or CheckSync Sync byte byte User byte sum A 16 bits 16 bits Byte 1 Byte 2 Byte 3 Byte 4 * Checksum B not applied to all Data Block types ^ Byte 3 is only reserved on sized data blocks. The Data Block is made up from the User Data. This consists of a variable number of data bytes optionally encoded to ensure secure delivery over a radio channel to the receiver. Checksum B is only applied at the end of sized Data Blocks, the receiver can then detect if any of the User Data has been corrupted. Checksum B is composed of 16 bits for messages 16 bytes and 32 bits for longer messages. 2004 CML Microsystems Plc 29 D/882/7 FRS Signalling Processor CMX882 1.5.5.3 Frame Head The Frame Head forms an important part of a frame as it allows the receiver to detect and lock on to MSK signals, provides basic addressing to screen out unwanted messages and indicates the format, coding and length of any following data. The 4 Control Field bytes have Forward Error Correction (FEC) applied to them in the transmitter, this adds 4 bits to every byte and the receiver can correct errors in the received bytes. The 4 received bytes are then checked for a correct CRC so corrupted Frame Heads can be rejected. If checksum A indicates that the Control Field bytes are correct, the Address (byte 1) is compared with that stored in the Device Address bits of register $C2. If a match occurs, or if the received address is '40' then an interrupt is raised indicating a valid Frame Head has been received. The Frame Head is 80 bits long (16 + 16 + {4x12}). 1.5.5.4 Data Block Coding The Data Block follows the Frame Head and can be coded with different levels of error correction and detection. The Data Block format is controlled by Frame Head byte 2, see also section 1.6.11. Messages can take the following formats: Type: 0 Description: Raw data, the CMX882 will transmit 16 bits at a time. In receive the device will search for the programmed 16 bit frame sync pattern and then output all following data 16 bits at a time, the host will have to perform all other data formatting. The data scrambler does not operate in this mode. This mode can be useful when interfacing to a system using a different format to those available in the CMX882. Frame Head only, no User Data will be added. This format can be useful for indicating channel or user status by using byte 3 and the User Bit of the Frame Head. Frame head followed by raw data. User data is appended to the Frame Head in 2 byte units with no formatting or CRC added by the CMX882. No size information is set in the Frame Head and User Data may contain any even number of bytes per Frame. Frame Head followed by FEC coded data only. Each byte of the User Data has 4 bits of FEC coding added. No size information is set in the Frame Head and User Data may contain any even number of bytes per Frame. No CRC is added to the data. Frame Head followed by FEC coded data with an automatic CRC at the end of the User Data. The number of User Data bytes in the Frame must be set in Frame Head byte 3. The CRC is automatically checked in the receiver and the result indicated to the host. Up to 255 bytes of User Data can be sent in each Frame using this format. As per `4' with the addition of all Data Block bytes being interleaved. This spreads the transmitted information over time and helps reduce the effect of errors caused by fading. Interleaving is performed on blocks of 4 bytes, the CMX882 automatically adds and strips out pad bytes to ensure multiples of 4 bytes are sent over the radio channel. 1 2 3 4 5 Notes: * Message types 1, 2 and 3 have no size information requirement and do not reserve Frame Head byte 3. This byte may be freely used by the host to convey information. In message types 4 and 5 this byte must be set to the number of User Bytes in the message attached to that Frame Head (255) to allow the receiver to correctly decode and calculate the CRC. * Type 0 data transfers do not use frame heads. In Tx the host must transfer the bit and frame sync data before sending the message data. In Rx the host must decode all data after the frame sync. When using type 0 (raw data) messages it is strongly recommended that the default Frame Sync pattern is not used. This is to reduce the loading on receivers using the formatted data types which would otherwise try to decode the 6 bytes following a type 0 frame sync as a Frame Head. * 2004 CML Microsystems Plc 30 D/882/7 FRS Signalling Processor CMX882 Table comparing different message types: Data Block Formatting Type: 2 3 4 5 Total overair bits for an 80 byte message 720 1040 1088 1088 Air time for FFSK message (ms) at at 1200b/s 2400b/s 600 300 867 433 907 907 453 453 Over air efficienc y 89% 62% 59% 59% Burst length protection at 1200b/s [for 2400b/s divide both times by 2] Probability of detecting errors Zero Poor Excellent Excellent None <0.83ms in any 10ms <0.83ms in any 10ms <3.33ms in any 40ms Higher levels of error protection have the penalty of adding extra bits to the over air signal and this reduces the effective bit rate. Less error protection increases the effective bit rate, however in typical radio conditions the penalty is a greater risk of errors leading to repeated messages and a net reduction in effective bit rate compared to using error correction and detection. 1.5.5.5 Data Scrambling / Privacy Coding It is preferable for MSK over air data to be reasonably random in nature to ensure the receiver can track timing using the bit changes and to smooth the frequency spectrum. To reduce the possibility of User Data causing long strings of 1's or 0's to be transmitted, a 16 bit data scrambler is provided and operates on all bits after the Frame Head. The default (standard) setting for this scrambler is with a start code (seed) of $FFFF and any receivers with the same seed may decode this data. However, if the transmitter and receiver pre-arrange a different seed then the scrambler will start its sequence in another place and any simple receiver that does not know the transmitted seed will not be able to successfully decode the data. This method gives over 65,000 different starting points and the chance of others decoding data successfully is reduced. The CMX882 provides the option of two custom 16 bit words that are programmable by the user in Program Register P0.2 to P0.5. Bits 0 and 1 in the Frame Head Format byte indicate which setting (standard, Seed1, Seed2 or none) the flowing Data Block has been scrambled with, see section 1.6.11. Note that a seed of $0000 will effectively turn off the scrambler and provide no protection against long sequences of 1's or 0's. Reception of scrambled data will only be successful when the receiving device has been programmed with the correct (identical) seed to that used by the transmitter. By using this method the CMX882 provides a privacy code that will protect against casual monitoring, however the data is not encrypted and a sophisticated receiver can decode the data by using moderately simple decoding techniques. If data encryption is required it must be performed by the host. The scrambler function is controlled by bits 0,1 of the Modem Control register ($C7). 1.5.5.6 Data Buffer Timing Data must be transferred at the rate appropriate to the signal type and data format. The CMX882 buffers signal data in up to two 16-bit registers. The CMX882 will issue interrupts to indicate when data is available or required. The host must respond to these interrupts within the maximum allowable latency for the signal type. Table 9 shows the maximum latencies for transferring signal data to maintain appropriate data throughput. 2004 CML Microsystems Plc 31 D/882/7 FRS Signalling Processor CMX882 Table 9 Maximum Data Transfer Latency Data encoding type 0 1 2 3 4 5 Max time to read from or write to data buffer 1200b/s 2400b/s 13.3ms 6.6ms N/A* N/A* 13.3ms 6.6ms 20ms 10ms 40ms 20ms 40ms 20ms Data buffer size 2 bytes 4 bytes 2 bytes 2 bytes 4 bytes 4 bytes * Type 1 message is an isolated Frame Head, there is no subsequent data to load (Tx) or read (Rx). 1.5.6 XTCSS Coding The CMX882 allows addressed calling using a 4 tone In-band tone burst followed by an optional subaudio `XTCSS maintenance tone' (at 64.7Hz). In transmit the CMX882 handles the transmission of the 4 tone sequence and the sub-audio tone. In receive the CMX882 will search for valid In-band tone sequences containing the previously programmed address. The over air signalling of XTCSS is shown below: XTCSS sub-audio A In-band tones Voice / Data Notes: * To reduce 'cut on' time with XTCSS voice calls, the host can enable the receive audio path at 'B' (as soon as the 4 tone sequence is available), before the sub-audio is detected. * XTCSS 4 tone sequences must be prefixed and suffixed with a silent 'no-tone' period of at least the length of each tone. See also programming register P1.1. In-band tones A1 and A0 are the BCD (binary coded decimal) representation of the Device Address bits of $C2 register, the valid XTCSS address range is 01 to 99, A0 is the least significant digit. The XTCSS address '40' is reserved for an all call address - regardless of the XTCSS address being searched for the CMX882 will always indicate when a valid 4 tone set containing address '40' has been received. In transmit the CMX882 will only generate the sub-audio maintenance tone when the CTCSS enable bit is also set to '0'. The sub-audio tone (if enabled) will be automatically output after the 4th XTCSS tone has been transmitted. An XTCSS interrupt is generated (if enabled) at point 'A' - see diagram above, the host should then wait one tone period before enabling the audio path (or transmitting data) to ensure sufficient no-tone suffix to the XTCSS 4 tone set. To summarize, detection of XTCSS sub-audio maintenance tone requires the CTCSS decoder to be enabled, whereas generation of the XTCSS sub-audio maintenance tone requires the CTCSS encoder to be disabled. In-band tone S0 is selected from the normal tone range of $B - $D to maintain compatibility with HSC type addressing. In-band tone S1 is selected from the normal tone range $0 - $9. The bit patterns for S0 and S1 indicate the type of information to follow according to the following tables: A1 A0 S0 S1 B 2004 CML Microsystems Plc 32 D/882/7 FRS Signalling Processor CMX882 In-band tone S0 Dec Hex 0-10 0-$A 11 $B 12 $C 13 $D In-band tone S1a Dec Hex 0-3 0-3 4 4 5 5 6 6 7 7 8 8 9-13 9-$D In-band tone S1b Dec Hex 0 0 1 1 2-13 2-$D Reserved, do not use for S0 Data or other silent (non-voice) call to follow, see S1a Voice to follow - see S1b Reserved, do not use for S0 User option for S1a MSK data to follow 1200b/s Formatted Blocks MSK data to follow 1200b/s Raw Data MSK data to follow 2400b/s Formatted Blocks MSK data to follow 2400b/s Raw Data End of XTCSS coded message (EOM) Reserved - do not use for S1a Voice message Compressed No Yes Reserved, do not use for S1b Note: Tone numbers in the above tables refer to the Normal tone column as defined in Table 6. Examples: Device address $22 $03 $2C Note: Over air 4 tones 34C0 03C1 4EB0 Meaning Address 34, Un-compressed voice to follow Address 03, Compressed voice to follow Address 44, Non voice, user option 0, (E is repeat character) For all XTCSS coding the CMX882 will add (in Tx) and strip out (in Rx) the repeat tone as required. The host C need only load or read out the normal tones listed in Table 6. 2004 CML Microsystems Plc 33 D/882/7 FRS Signalling Processor CMX882 1.5.7 C-BUS Operation This block provides for the transfer of data and control or status information between the CMX882's internal registers and the C over the C-BUS serial interface. Each transaction consists of a single Register Address byte sent from the C which may be followed by one or more data byte(s) sent from the C to be written into one of the CMX882's Write Only Registers, or one or more data byte(s) read out from one of the CMX882's Read Only Registers, as illustrated in Figure 12. Data sent from the C on the Command Data line is clocked into the CMX882 on the rising edge of the Serial_Clock input. Reply Data sent from the CMX882 to the C is valid when the Serial_Clock is high. The CSN line must be held low during a data transfer and kept high between transfers. The C-BUS interface is compatible with most common C serial interfaces and may also be easily implemented with general purpose C I/O pins controlled by a simple software routine. The number of data bytes following an A/C byte is dependent on the value of the A/C byte. The most significant bit of the address or data are sent first. For detailed timings see section 1.8.1. C-BUS Write: See Note 1 CSN Serial_Clock CMD_DATA 7 MSB See Note 2 6 5 4 3 2 1 0 LSB 7 MSB 6 ... 0 LSB 7 MSB ... 0 LSB Address / Command byte REPLY_DATA High Z state Upper 8 bits Lower 8 bits C-BUS Read: See Note 2 CSN Serial_Clock CMD_DATA 7 MSB 6 5 4 3 2 1 0 LSB Address byte REPLY_DATA High Z state Upper 8 bits 7 MSB Lower 8 bits 7 MSB 6 ... 0 LSB ... 0 LSB Data value unimportant Repeated cycles Either logic level valid Figure 12 C-BUS Transactions Notes: 1. For Command byte transfers only the first 8 bits are transferred ($01 = Reset). 2. For single byte data transfers only the first 8 bits of the data are transferred. 3. The CMD_DATA and REPLY_DATA lines are never active at the same time. The Address byte determines the data direction for each C-BUS transfer. 4. The Serial_Clock input can be high or low at the start and end of each C-BUS transaction. 5. The gaps shown between each byte on the CMD_DATA and REPLY_DATA lines in the above diagram are optional, the host may insert gaps or concatenate the data as required. 2004 CML Microsystems Plc 34 D/882/7 FRS Signalling Processor CMX882 1.6 1.6.1 C-BUS Register Description C-BUS Register Summary C-BUS Write Only Registers ADDR. (hex) $01 $B0 $B1 $B2 $B3 $C0 $C1 $C2 $C3 $C7 $C8 $CA $CB $CD $CE $CF REGISTER C-BUS RESET ANALOGUE GAIN SIGNAL ROUTING AUXILIARY ADC THRESHOLDS AUXILIARY ADC CONTROL POWER DOWN CONTROL MODE CONTROL AUDIO & DEVICE ADDRESS CONTROL TX TONE MODEM CONTROL PROGRAMMING REGISTER TX DATA 1 XTCSS & TX DATA 2 AUDIO TONE INTERRUPT MASK RESERVED REGISTER ADDRESS Word Size (bits) 0 16 16 16 8 16 16 16 16 16 16 16 16 16 16 16 The C-BUS address $CF is allocated for production testing and must not be accessed in normal operation. C-BUS Read Only Registers ADDR (hex) $B4 $C5 $C6 $C9 $CC Interrupt Operation The CMX882 will issue an interrupt on the IRQN line when the IRQ bit (bit 15) of the Status register and the IRQ Mask bit (bit 15) are both set to `1'. The IRQ bit is set when the state of the interrupt flag bits in the Status register change from a '0' to '1' and the corresponding mask bit(s) in the Interrupt Mask register is(are) set. All interrupt flag bits in the Status register except the Programming Flag (bit 0) are cleared and the interrupt request is cleared following the command/address phase of a C-BUS read of the flag register. The Programming Flag bit is set to '1' only when it is permissible to write a new word to the Programming register. REGISTER AUXILIARY ADC DATA RX DATA 1 STATUS XTCSS & RX DATA 2 TONE STATUS Word Size (bits) 8 16 16 16 16 2004 CML Microsystems Plc 35 D/882/7 FRS Signalling Processor CMX882 1.6.2 $01 C-BUS RESET: address only. The reset command has no data attached to it. It sets the device registers into the states listed below. Addr. $B0 $B1 $B2 $B3 $B4 $C0 $C1 $C2 $C3 $C5 $C6 $C7 $C8 $C9 $CA $CB $CC $CD $CE $CF REG. ANALOGUE GAIN SIGNAL ROUTING AUXILIARY ADC THRESHOLDS AUXILIARY ADC CONTROL AUXILIARY ADC DATA POWER DOWN CONTROL MODE CONTROL AUDIO & DEVICE ADDRESS CONTROL TX TONE RX DATA 1 STATUS MODEM CONTROL PROGRAMMING REGISTER XTCSS & RX DATA 2 TX DATA 1 XTCSS & TX DATA 2 TONE STATUS AUDIO TONE INTERRUPT MASK Reserved Register Address 15 14 13 12 11 10 9 0 0 1 0 0 1 0 0 1 0 0 1 0 0 1 0 0 1 0 0 1 8 0 0 1 7 0 0 0 0 X 0 0 0 0 X 0 0 0 0 0 0 0 0 0 0 6 0 0 0 0 X 0 0 0 0 X 0 0 0 0 0 0 0 0 0 0 5 0 0 0 0 X 0 0 0 0 X 0 0 0 0 0 0 0 0 0 0 4 0 0 0 0 X 0 0 0 0 X 0 0 0 0 0 0 0 0 0 0 3 0 0 0 2 0 0 0 1 0 0 0 0 X 0 0 0 0 X 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 X 0 0 0 0 X 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 X 0 0 0 0 0 0 0 0 0 0 0 0 0 0 X 0 0 0 0 0 0 0 0 0 0 0 0 0 0 X 0 0 0 0 0 0 0 0 0 0 0 0 0 0 X 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 00 XX 00 00 0 0 00 XX 00 00 00 00 00 00 00 00 00 00 00 XX 00 00 00 00 00 00 00 00 00 00 00 XX 00 00 00 00 00 00 00 00 00 00 Following a general reset all of the programming registers (P0 - P4) are reset to zero except the following: P0.0 P0.1 P0.6 P0.7 P4.7 Frame Sync LSB Frame Sync MSB Bit Sync LSB Bit Sync MSB Transmit Limiter Control 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1 1 1 1 0 0 0 0 0 1 1 0 1 0 0 0 0 1 1 1 1 0 0 1 1 1 1 - This initiates the device with the MSK frame sync pattern of $CB23 and bit sync of alternate 1's and 0's. The transmit limiter value is initialised to the maximum limit. To initialise the device following power-up, or to clear the current device state, apply the following sequence of C-Bus actions: 1. Send a C-Bus Reset command. 2. Send $2001 to the Mode Control register (C-Bus address $C1). 3. Send $0000 to the Mode Control register. The device is now ready to be configured for its next application. 2004 CML Microsystems Plc 36 D/882/7 FRS Signalling Processor CMX882 1.6.3 Bit: $B0 ANALOGUE GAIN: 16-bit write-only 15 Inv_1 14 13 MOD_1 Attenuation 12 11 Inv_2 10 9 MOD_2 Attenuation 8 7 0 6 5 Input Gain 4 3 2 1 0 Audio Output Attenuation Bits 15 and 11 set the phase of the MOD_1 and MOD_2 outputs. When set to '0' the 'true' signal (0 phase shift) will be produced, when set to '1' the signal will be inverted (180 phase shift). This can be useful when interfacing with rf circuitry or when generating an inverted turn off coe for CTCSS. Any change will take place immediately after these bits are changed. The output paths provide user programmable attenuation stages to independently adjust the output levels of the modulators. Finer level control of the MOD_1 and MOD_2 outputs can be achieved with the FINE OUTPUT GAIN 1 and FINE OUTPUT GAIN 2 registers (P4.2-3). Bit 14 Bit 13 Bit 12 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 MOD_1 Output Attenuation >40dB 12dB 10dB 8dB 6dB 4dB 2dB 0dB Bit 10 0 0 0 0 1 1 1 1 Bit 9 0 0 1 1 0 0 1 1 Bit 8 0 1 0 1 0 1 0 1 MOD_2 Output Attenuation >40dB 12dB 10dB 8dB 6dB 4dB 2dB 0dB Bit 7 is reserved - set to 0. Bits 6 to 4 control the input path programmable gain stage - useful when amplifying low power voice signals from the microphone inputs. Finer gain control can be achieved with the `FINE INPUT GAIN' control register (P4.0). In receive mode it is recommended to set the gain to 0dB. Bit 6 0 0 0 0 1 1 1 1 Bit 5 0 0 1 1 0 0 1 1 Bit 4 0 1 0 1 0 1 0 1 Input Gain 0dB 3.2dB 6.4dB 9.6dB 12.8dB 16.0dB 19.2dB 22.4dB Bit 3 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 Bit 2 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 Bit 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 Bit 0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 Audio Output Attenuation >60dB 44.8dB 41.6dB 38.4dB 35.2dB 32.0dB 28.8dB 25.6dB 22.4dB 19.2dB 16.0dB 12.8dB 9.6dB 6.4dB 3.2dB 0dB Bits 3 to 0 control the output path programmable attenuation stage to adjust the volume of the audio output signal. Finer volume control can be achieved with the `FINE OUTPUT GAIN 1' control register (P4.2). 2004 CML Microsystems Plc 37 D/882/7 FRS Signalling Processor CMX882 1.6.4 Bit: $B1 SIGNAL ROUTING: 16-bit write-only 15 0 14 0 13 12 11 0 10 0 9 0 8 0 7 0 6 0 5 4 3 2 1 Ramp Up 0 Ramp Down Tx MOD_1 and MOD_2 Routing Analogue i/p select AUDIO o/p select Bits 15 and 14 reserved - set to 0. Bits 13 and 12 select the routing of the transmit signals allowing 1 or 2 point modulation and interfaces. Bit 13 0 0 1 1 Bit 12 0 1 0 1 Tx MOD_1 and MOD_2 routing Tx, MOD_1 and MOD_2 outputs set to bias. Tx, In band signals to MOD_1, Subaudio signals to MOD_2 Tx, In band and Subaudio to MOD_1, MOD_2 set to bias Tx, In band and Subaudio to both MOD_1 and MOD_2 `In-band' in this context refers to any of the signals; Voice, In-band tone etc. Bits 11 to 6 are reserved - set to 0. Bit 5 0 0 1 1 Bit 3 0 0 1 1 Bit 4 0 1 0 1 Bit 2 0 1 0 1 Analogue Input select No input selected (Input = VBIAS) Input amplifier 2 (Input_2 i/p) Microphone (MIC i/p) Discriminator (DISC i/p) AUDIO Output select No output selected (Output = VBIAS) Received Voice signal MOD_1 signal (for Tx monitoring) Reserved, do not use When bits 1 or 0 are set to '1' output signals are ramped up (bit 1) or ramped down (bit 0) to reduce transients in the transmitted signal. Time to ramp up / down is set in the 'Ramp Rate Control' section of the Programming register (P4.6). 1.6.5 Bit: $B2 AUXILIARY ADC THRESHOLDS: 16-bit write-only 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 High Threshold [Range: 0 to 255] Low Threshold [Range: 0 to 255] If the selected signal level exceeds the High Threshold, the `Signal High' bit of the Status register will be set to 1. If the Signal level falls below the Low Threshold, the `Signal Low' bit of the Status register will be set to 1. If the corresponding interrupt bit is enabled, a C-BUS interrupt will be generated. These status bits are cleared when the Status register is read. The behaviour of the CMX882 is not defined if the high threshold is less than the low threshold. Threshold resolution: Threshold accuracy: Differential linearity: VDD(A)/256 per LSB 2 LSB 1 LSB [monotonic] The `Auxiliary ADC Thresholds' register must not be updated whilst the Auxiliary ADC is enabled. 2004 CML Microsystems Plc 38 D/882/7 FRS Signalling Processor CMX882 1.6.6 Bit: $B3 AUXILIARY ADC CONTROL: 8-bit write-only 7 6 5 4 3 2 1 0 Aux ADC i/p select Conversion Interval The `Conversion Interval' (bits 5 to 0) defines the time between measurements whilst the Auxiliary ADC is enabled. This allows the user to trade-off device power consumption with response time. (approximate) = 0.5mW/VDD(A)/conversion (approximate) = 20.8s per LSB. The user should set an interval to ensure that no part of a received signal is missed, so that the signal type can be correctly identified. If using the Rx Auto start-up feature the recommended maximum Conversion Interval is 125s. The `Auxiliary ADC' register must not be updated whilst the Aux ADC is enabled. Auxiliary ADC power Conversion Interval The Aux ADC i/p select (bits 7 to 6) control the input to the Auxiliary ADC. Control is independent of the Analogue i/p select bits and hence the Aux ADC can monitor any one of the 4 inputs independently. Bit 7 0 0 1 1 1.6.7 Bit: Bit 6 0 1 0 1 Auxiliary ADC input from: Signal monitor (Sig_Monitor i/p) Input amplifier 2 (Input_2 i/p) Microphone (MIC i/p) Discriminator (DISC i/p) $C0 POWER DOWN CONTROL: 16-bit write-only 15 Input_2 amp 14 MIC amp 6 BIAS 13 Disc amp 5 Signal Processing 12 Input Gain 4 Prog Reg Save 11 Output Fine Gain 1 3 Xtal_N 10 Output Fine Gain 2 2 Clock_Out_N 9 O/P Coarse Gain 1 1 Enable Aux ADC 8 O/P Coarse Gain 2 0 Rx Auto start-up Bit: 7 Audio Output Bits 15 to 5 provide the power control of the specified blocks. If a bit is '1', the corresponding block is on, else it is powered down. A C-BUS or Power up reset clears all bits in this register to '0'. If bit 5 is '0' the internal signal processing blocks are reset and placed into a power-save mode. Bit 4 should be set to a '1' if any of the program registers (1.6.20) have been programmed as this prevents them being reset after a Rx Auto start-up or when the Signal Processing blocks come out of power save. If bit 4 is set to '0' the program registers will be reset to the C-BUS or Power-up reset state whenever the Signal Processing blocks come out of power save. Bits 3 and 2 control the xtal clock circuit. The xtal circuit is powered down by setting bit 3 to '1'. Note: The Clock/Xtal pin may be driven by an external clock source regardless of the setting of these bits. The Clock_Out pin is disabled (held low) by setting bit 2 to `1'. After a Power-up or C-BUS reset bits 2 and 3 are cleared to `0', so that both the xtal circuit and clock output are enabled. Bit 1 controls the Auxiliary ADC. If set to '1' the Auxiliary ADC will generate interrupts in accordance with the settings of the interrupt mask bits. If bit 1 is '0' the Auxiliary ADC is disabled and powered down. Bit 0 controls Rx Auto start up. If bit 0 is set to '1' and the Aux ADC input rises above the `High Threshold' the device will automatically enter receive mode and initiate Rx signal type identification for those signals enabled in the Mode register. The correct Aux ADC input, Rx signal routing and power down bits must be set for automatic receive start up to operate, the mode control bits should be set to '00' in this case. If bit 0 is cleared to '0' the CMX882 will not automatically start-up and it is up to the host to respond to Aux ADC interrupts in this case. Bit 0 must be set to '0' whilst writing through register $C8 Programming Register. 2004 CML Microsystems Plc 39 D/882/7 FRS Signalling Processor CMX882 1.6.8 Bit: $C1 MODE CONTROL: 16-bit write-only 15 Enable Voice 14 13 12 Generate Audio Tone 4 Enable 2400b/s 11 Enable CTCSS 3 Enable 1200b/s 10 Enable DCS 9 Enable DCS Inverse 1 Mode Select 8 0 In band signalling: In-band tone, XTCSS 6 0 5 0 Bit: 7 0 2 0 0 Bits 1 and 0 control the overall mode of the CMX882 according to the table below: Bit 1 0 0 1 1 Bit 0 0 1 0 1 Device Mode Idle Receive Mode Transmit Mode Reserved - do not use During transmit, only one signal type may be enabled for each of the sub-audio and voice bands, see Table 7. During receive the CMX882 will search for all signals enabled in this register and report those that are successfully decoded. See also Table 2 in section 1.5.3. In transmit mode the CMX882 begins transmission of a selected signal immediately after it has been enabled. The host C must ensure all associated data and control bits have been set to their required values before enabling the signal in this register. Bits 4 and 3 control the modem functions of the CMX882 in accordance with the following table: Bit 4 0 0 1 1 Bit 3 0 1 0 1 Tx - Transmitted signal None MSK 1k2b/s MSK 2k4b/s Reserved Rx - Monitored signal(s) None MSK 1k2b/s MSK 2k4b/s MSK 1k2 & 2k4b/s In transmit mode data transmission will start or finish (regardless of whether all data has been transmitted) immediately after the modem control bits are changed. To transmit a second data message the modem control bits must be set to '0', data bytes for the following message loaded, and the required bits set to '1'. Bits 2 and 5 to 8 are reserved - set to '0'. Bits 11 to 9 determine the sub-audio transmission / reception signalling: Bit 11 0 0 0 0 1 1 1 1 Bit 10 0 0 1 1 0 0 1 1 Bit 9 0 1 0 1 0 1 0 1 Tx - Transmitted signal: No Sub-Audio Transmitted Inverted DCS* DCS Do not use CTCSS Do not use Do not use Do not use Rx - Monitored signal(s): No Sub-audio Monitoring Inverted DCS* DCS DCS + inv DCS* CTCSS CTCSS + inv DCS* CTCSS + DCS CTCSS + DCS + inv DCS* * See Table 4 DCS Modulation Modes. Bit 12 enables Audio tone generation (see section 1.6.14). This operates in transmit and receive modes. In transmit mode this bit will only enable the Audio Generator when no other voice band signals are being transmitted i.e. bits 14, 13, 4 and 3 set to '0'. 2004 CML Microsystems Plc 40 D/882/7 FRS Signalling Processor CMX882 Bits 14 and 13 determine the voice band tone transmission and reception. When transmitting or receiving audio band signals the voice path must be disabled by clearing `Voice Enable' bit 15 to '0'. Bit 14 0 0 1 1 Bit 13 0 1 0 1 Tx - Transmitted signal No voice band tone transmitted In-band tone Reserved XTCSS Rx - Monitored signal No voice band tones monitored In-band tone Reserved XTCSS When set to '1', bit 15 enables the voice path. In transmit mode the selected audio input is routed to the modulator outputs. In receive mode the voice processing path is enabled to the audio output. In transmit mode bit 15, if set to '1', will be temporarily disabled (cleared to '0') whenever any of the bits 3, 4, 12, 13 and 14 are set to '1'. In receive mode bit 15, if set to '1', will be temporarily disabled (cleared to '0') whenever bit 12 is set to '1'. It is up to the host C to control bit 15 when voice band signals are received. The Mode Control register ($C1) may be written to at any time (subject to C-BUS timing restrictions). If the enable bit of the currently decoded signal is disabled whilst in phase 2 the CMX882 will return to phase 1 for that band. If the same signal needs to be searched for again then the appropriate bit needs to be set back to `1' in $C1. However, to de-emphasise in-band tones, bit 15 must be set to `1'. The CMX882 will only detect signals when their amplitude is above the threshold set for each band (subaudio and voice), as set in the program registers. Therefore even if valid tones or signals are present the CMX882 will ignore them unless they exceed the detect threshold. Time and level hysteresis is applied to reduce chattering in marginal conditions. Detection strategies used by the CMX882 whilst in receive mode: When in receive mode the CMX882 treats the received signal in two bands; Sub-audio (60-260Hz) and voice band (300-3kHz). For the sub-audio the CMX882 can monitor and decode CTCSS and DCS signals in parallel. Because certain FFSK bit patterns can mimic some In-band tones the In-band receiver is temporarily disabled when an FFSK frame sync is detected. If using sized packets (type 1, 4 and 5) the CMX882 will automatically restore In-band tone detection when the received message has ended. If using unsized packets (type 0, 2 and 3) the host must monitor the received data and restore XTCSS / In-band tones (by setting bits 14 and 13 as required) when it has detected the end of data. 2004 CML Microsystems Plc 41 D/882/7 FRS Signalling Processor CMX882 1.6.9 Bit: 15 0 $C2 AUDIO & DEVICE ADDRESS CONTROL: 16-bit write-only 14 Scramble 13 Compand 12 11 10 9 8 7 6 5 4 3 2 1 0 Special Sub-Audio Voice filter mode Device Address Bit 14 controls the audio band scrambler. When set to `1' voice signals are scrambled, by frequency inversion, in transmit and receive modes. When set to `0' no scrambling is performed. Bits 7 to 0 define the device address. This setting is used for the CTCSS and XTCSS address in both Tx and Rx modes and as the receive MSK frame head address. The range of valid addresses is: CTCSS tone (1-51 in decimal), MSK address (1-255 in decimal) and XTCSS (1-99 in decimal). In Tx this number will be used to select the addressing of the enabled signal, if the address is outside the valid range no signalling will occur. In Rx this address (along with the all-call address of '40') will be searched for each signalling format enabled in the Mode register. The detected signal type will be reported in the Status register $C6 and the address will be indicated in the appropriate Rx Data register $C5 or $C9, or the Tone Status register $CC. Bits 9 to 8 select special sub-audio tones in accordance with the following table. Selecting the `DCS turn off tone' during DCS transmit will cause the DCS turn off tone to be transmitted; this will override the DCS data being transmitted. `DCS turn off tone' must be selected in this register to enable detection of the DCS turn off tone during receive. To transmit the 64.7Hz XTCSS maintenance tone, XTCSS transmit must be selected in the Mode Control register and XTCSS maintenance tone must be selected in this register. Transmission of the maintenance tone overrides any other CTCSS tone being transmitted. The XTCSS maintenance tone decoder is enabled by selecting XTCSS receive mode, so it is not necessary to TM select the XTCSS maintenance tone in this register when receiving. If the Tone Clone mode is selected this allows the device in Rx to non-predictively detect any CTCSS frequency in the range of valid tones, the received tone number will be reported in the Tone Status register $CC. Bit 9 0 0 1 1 Bit 8 0 1 0 1 Freq (Hz) 134.4 64.7 Clone Special Sub-Audio tone None DCS turn off tone XTCSS maintenance tone (Tx Only) CTCSS Tone clone mode (Rx only) The voice filter control bits 12 and 11 determine the Voice Band Filter mode applied to the voice signal before it is transmitted or after it has been received. Bit 10 controls the de-emphasis (Rx) or preemphasis (Tx) mode of the voice band filtering. Bit 12 X X 0 0 1 1 Bit 11 X X 0 1 0 1 Bit 10 0 1 X X X X Voice filter mode Disable de/pre-emphasis Enable de/pre-emphasis No filtering applied 12.5kHz channel filtering 25.0kHz channel filtering Reserved - do not use Bit 13 controls the audio band compandor. When set to '1' audio band signals are compressed in transmit mode and expanded in receive mode. When set to '0' no companding is performed. Bits 14 to 15 are reserved, set to '0'. 2004 CML Microsystems Plc 42 D/882/7 FRS Signalling Processor CMX882 1.6.10 Bit: $C3 Tx In-Band Tones: 16-bit write-only 15 14 13 12 11 10 0 9 0 8 0 7 0 6 0 5 0 4 0 3 0 2 0 1 0 0 0 Tx In-band tone Bits 15 to 11 define the tone transmitted when Tx In-band tone is enabled. The frequency is as defined in Table 6 In-band Tones. Bits 10 to 1 are reserved, set to '0'. 1.6.11 Bit: $C7 Modem Control: 16-bit write-only 15 0 14 0 13 0 12 0 11 0 10 Type 0 format 9 Last Tx data 8 0 7 6 5 4 0 3 0 2 User bit 1 0 MSK message format Scramble seed This register configures the way the CMX882 handles MSK data in both transmit and receive. Bits 15 to 11, 8, 4 and 3 are reserved, set to '0'. Bit 10 sets the raw data mode when set to '1'. When set to '0' the built in data packeting is enabled. The way this bit is set determines how the CMX882 handles new data when transmit and receive modes: Bit 10, Receive mode: * * If Bit 10 is `1' the device will look for the programmed Frame Sync. pattern, raise an interrupt (if enabled) and decode the following data 16 bits at a time, making them available in register $C5. If Bit 10 is `0' the device will look for a complete Frame Head before raising an interrupt (if enabled) and then decode the following data in accordance with the received message format. The Frame Head Control Field bytes, User Data and any CRC will be presented in registers $C5 and $C9. If Bit 10 is `1' the device will transmit data 16 bits at a time from register $CA. Bit and frame sync pattern generation and all formatting of the data have to be performed by the host in this case. If Bit 10 is `0' the device will transmit the programmed bit and frame sync patterns followed by a Frame Head containing the information supplied in bits 7-0 of this register and the 2 bytes in register $CA. Subsequently the host must supply data when requested to complete the transmission of the data packet as defined in the Frame Head bytes. Bit 10, Transmit mode: * * Bit 9 is only valid when transmitting data with type 0, 2 or 3 formatting and indicates to the CMX882 that it can cease modulation. The host must set this bit to '1' immediately after the interrupt for `load more data' occurs. In receive, or when transmitting other message formats, this bit must be set to '0'. When bit 10 = `0' bits 7-0 control the format and coding used for MSK messages: (See also section 1.5.5.) Bits 7 to 5 control the data formatting used by the CMX882 in transmit and receive: Bit 7 0 0 0 1 1 Bit 6 Bit 5 Type 1 2 3 4 5 Message format: Frame Head only, no payload Frame Head + Unsized payload of raw 16 bit words Frame Head + Unsized payload with FEC Frame Head + Sized payload with FEC + CRC Frame Head + Sized payload with FEC + CRC + interleaving Reserved 0 1 1 0 1 1 0 0 0 1 All other patterns 2004 CML Microsystems Plc 43 D/882/7 FRS Signalling Processor CMX882 Bit 2 is a User bit and may be freely used by the host. This bit has no effect on the message format or encoding and will be reported in the Rx Data register for the receiving host to use as appropriate. This bit could be used to indicate a special message, e.g. one containing handset or channel set-up information. Bits 1-0 select the data scrambler seed used when transmitting User Data. The receiving CMX882 will automatically de-scramble the received User Data using the setting indicated in the received Frame Head. The receiving host can read the scrambler setting (0-3) used by the transmitter via register $C9 and may use this when returning messages. See also section 1.5.5.5. Bit 1 0 0 1 1 1.6.12 Bit: Bit 0 0 1 0 1 MSK data scrambling setting: Standard scrambling (seed = $FFFF) Scramble Seed1 (see P0.2-3) Scramble Seed2 (see P0.4-5) No scrambling (seed = $0000) $C8 PROGRAMMING REGISTER: 16-bit write-only 15 First Word 14 Block Number 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Block / Data Programming Data See section 1.6.20 for a description of this register. 2004 CML Microsystems Plc 44 D/882/7 FRS Signalling Processor CMX882 1.6.13 Bit: $CA $CB* $CA and $CB TX DATA & XTCSS Codes: 2 x 16-bit write-only 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Tx MSK Data Byte 0 (Frame Head: Address byte) Tx Data Byte 2* XTCSS Tone 3 (S1) XTCSS Tone 2 (S0) 0 0 0 Tx MSK Data Byte 1 (Frame Head: Size / Information byte) Tx Data Byte 3* 0 0 0 0 0 *Register $CB is only used for Type 4 and 5 data formats and Frame Heads, the Tx buffer is effectively 4 bytes long in these cases. These 2 words hold next 2 bytes (Byte 0 and 1) or 4 bytes (Bytes 0, 1, 2 and 3) of MSK data to be transmitted. Outgoing data is continuous, if new data is not provided before the current data has been transmitted the current data will be re-transmitted, until new data is provided. Transmission of current data will be completed before transmission of newly loaded data begins. See section 1.5.5.6. $CB holds the codes to be used when transmitting an XTCSS type tone set. Each 4 bits define the Inband tone used, see Table 6 In-band Tones. S0 and S1 are the information section of the 4 tone set. This register must be set to the required value before XTCSS transmission is enabled. For more details see section 1.5.6. Note The address used is defined in the Audio & Device Address Control register. Although $CB holds both Tx data and Tx XTCSS tone information, these functions can not be used simultaneously so no conflict will occur. When transmitting formatted data packets the host must first load the correct Address and Size / Information bytes for the following packet into register $CA. The CMX882 will automatically add the Control byte (based on the settings in register $C7) and calculate the Frame Head Checksum A byte. The CMX882 will read the Size and Message formatting information and automatically format all following data; adding error correction bytes, adding pad bytes, interleaving, scrambling and calculating and appending Checksum B as required. The only task the host need perform during the transmission of a Frame is to download new data when it is required. Note: These 2 words must be written separately. i.e. Two 16 bit C-BUS transactions. 1.6.14 Bit: $CD AUDIO TONE: 16-bit write only 15 0 14 0 13 0 12 0 11 10 9 8 7 6 5 4 3 2 1 0 Audio Tone When the required bits of the Mode Control register ($C1) are set an audio tone will be generated with the frequency set by bits (11-0) of this register in accordance with the formula below. If bits 11-0 are programmed with '0' no tone (i.e. Vbias) will be generated when the Audio Tone is enabled. frequency = Audio Tone (i.e. 1Hz per LSB) The Audio Tone frequency must only be set to generate frequencies from 300Hz to 3000Hz. The host must suppress other voice band signalling and set the correct audio routing before generating an audio tone and re-enable signalling and audio routing on completion of the audio tone. The timing of intervals between these actions is also controlled by the host C. This register may be written to whilst the audio tone is being generated, any change in frequency will take place after the end of the C-BUS write to this register. This allows complex sequences (e.g. ring or alert tunes) to be generated for the local speaker (Tx or Rx via the AUDIO pin) or transmitted signal (Tx via the MOD1/2 pins). 2004 CML Microsystems Plc 45 D/882/7 FRS Signalling Processor CMX882 1.6.15 Bit: $CE INTERRUPT MASK: 16-bit write-only 15 IRQ MASK 14 0 13 12 11 10 9 8 Rx CTCSS Rx In-band XTCSS MASK detect MASK detect MASK 5 0 4 Rx 2400b/s detect MASK 3 Rx 1200b/s detect MASK Rx DCS Aux ADC High Aux ADC Low detect MASK MASK MASK 2 0 1 0 0 Prog Flag MASK Bit: 7 FFSK end MASK 6 Data transfer MASK Bit 15 14 13 Value 1 0 1 0 1 12 11 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 10 9, 8 7 6 5 4 3 2, 1 0 Function Enable selected interrupts Disable all interrupts (IRQN pin not activated) Reserved - Set to 0 Enable interrupt when a change to a In-band tone is detected as indicated by a '0' to '1' change of bit 13 of the Status register Disabled Enable interrupt when a valid XTCSS 4 tone set is detected or has finished being transmitted as indicated by a '0' to '1' change on bit 12 of the Status register Disabled Enable interrupt when a change to a programmed CTCSS tone is detected as indicated by a '0' to '1' change of bit 11 of the Status register Disabled Enable interrupt on a change in the detect status of the DCS decoder as indicated by a '0' to '1' change of bit 10 of the Status register Disabled Enable interrupt when the corresponding Aux ADC status bit changes Disabled Enable interrupt when FFSK data transmission has ended Disabled Enable interrupt when an FFSK data transfer is required Disabled Reserved - Set to 0 Enable interrupt when valid 2400b/s data is detected Disabled Enable interrupt when valid 1200b/s data is detected Disabled Reserved - Set to 0 Enable interrupt when Prog Flag bit of the Status register changes from '0' to '1' (see Programming register $C8) Disabled 2004 CML Microsystems Plc 46 D/882/7 FRS Signalling Processor CMX882 The following 5 registers (including 2 receive data registers) are read only 1.6.16 Bit: $B4 AUX ADC MONITOR DATA: 8-bit read-only 7 6 5 4 3 2 1 0 Signal Monitor Data This data holds the result of the last measurement performed by the auxiliary ADC. The signal processor must be on to read Aux ADC data, so Power Down Control register b5 must be set to `1'. This is independent of whether Tx or Rx modes are selected. 1.6.17 Bit: $C6 STATUS: 16-bit read-only 15 IRQ 14 0 13 In-band tone state change 5 Block CRC error 12 XTCSS 4 tone set complete 4 11 CTCSS state change 3 10 DCS state change 2 9 Aux ADC Monitor High 8 Aux ADC Monitor Low Bit: 7 End of FFSK data 6 FFSK data transfer required 1 0 Programming Flag Rx 2400b/s Rx 1200b/s 0 0 This word holds the current status of the CMX882: the value read out is only valid when bit 5 of the Power Down Control register ($C0) is set to '1'. Changes in the Status register will cause the IRQ bit (bit 15) to be set to '1' if the corresponding interrupt mask bit is enabled. An interrupt request is issued on the IRQN pin when the IRQ bit is '1' and the IRQ MASK bit (bit 15 of register $CE) is set to '1'. Bits 1 to 15 of the Status register are cleared to '0' after the Status register is read. Bit 0 is only cleared by writing to the Programming Register. Bits 14 and 2 to 1 are reserved. Bits 13, 11 and 10 indicate that a In-band tone, CTCSS or DCS event caused the interrupt, the host should then read the Tones Status register ($CC) for further information. In transmit these bits will be set to '0'. Detection of the DCS turn off tone and removal of the DCS turn off tone are both flagged as DCS events in the Status register, not as CTCSS events. The assertion or removal of the `XTCSS Maintenance Tone' (64.7Hz) is flagged as a CTCSS event. In receive bit 12 indicates that a valid XTCSS 4 tone set with the correct addressing (see $C2) has been detected, the 4 received tones are indicated in $C9. In Tx mode bit 12 will be set to '1' at the end of the th 4 XTCSS tone transmitted. Aux ADC High (bit 9) and Aux ADC Low (bit 8) reflect the recent history of the Aux ADC level, with respect to the high and low thresholds. The most recent Aux ADC reading can be read from $B4. Aux ADC Monitor High 0 0 1 1 Aux ADC Monitor Low 0 1 0 1 Aux ADC history since last reading: Neither threshold crossed Signal gone below low threshold Signal gone above high threshold Signal gone below low threshold and above high threshold In Rx mode bit 7 will be set at the same time as bit 6 after receiving the last part of a sized FFSK Frame or Type 1 (frame head only) message, bit 5 (CRC) will also be updated at this time. When the host detects bit 7 is set it may power down the CMX882 or set the CMX882 to transmit or receive new information as appropriate. 2004 CML Microsystems Plc 47 D/882/7 FRS Signalling Processor CMX882 In Tx mode bit 7 will be set when the last bit of FFSK data has been transmitted. Note; when using type 0, 2 or 3 data formats (see section 1.5.5.4) this bit will only be set if bit 9 of the Modem Control register ($C7) is set at the appropriate time. After allowing a short time delay associated with the external components and radio circuitry, the host may power down the CMX882 and transmitter or set the CMX882 to transmit or receive new information as appropriate. Bit 6 indicates that new transmit data is required (in Tx mode) or received data is ready to be read (in Rx mode). For continuous transmission or reception of information, a data transfer should be completed within the time appropriate for that data (see Table 9). Bit 5 will be set after receiving the CRC portion of a sized Data Block (types 4 and 5) and will be set to `0' when the locally calculated CRC indicates the received data has no errors. Bits 4 and 3 indicate the received data rate after a valid data sequence has been received. If data Type 0 formatting is enabled these bits will be set on detection of a valid frame sync pattern. If Type 0 formatting is disabled then these bits will only be set when a Frame Head is detected with a correct CRC. Rx 2400b/s 0 0 1 1 Rx1200b/s 0 1 0 1 Bit rate of detected valid data: No data 1200b/s 2400b/s Reserved Programming Flag, bit 0: The Programming Register ($C8) should only be written to when bit 0 is set to '1' (with both Mode select bits set low - See register $C8). Writing to the Programming Register ($C8) clears bit 0 to '0'. Bit 0 is restored to '1' when the programming action is complete, normally within 250s, when it is then safe to write to the Programming Register. 1.6.18 Bit: $C5 $C5 and $C9 RX DATA: 2 x 16-bit read-only 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Rx Data Byte 0 (Frame Head: Address byte) Rx Data Byte 2* (Frame Head: Size / Information byte) XTCSS Tone 3 (S1) XTCSS Tone 2 (S0) Rx Data Byte 1 (Frame Head: Format byte) Rx Data Byte 3* (Frame Head: CRC byte) XTCSS received address $C9 *$C9 is used when receiving Type 4 and 5 formats and Frame Heads, the Rx buffer is effectively 4 bytes long in these cases. These 2 words hold the most recent 2 bytes (Byte 0 and 1) or 4 bytes (Bytes 0, 1, 2 and 3) of MSK data decoded. Received data is continuous, if the data is not read before the next data is received the current data will be over-written. $C9 holds the information decoded after receiving an XTCSS type tone set. Bits 7 to 0 represent the received address in hex based on the XTCSS tones A1 and A0. This register will only be updated if the received address matches the one programmed in the Audio and Device Address Control register or is the all call address of '40'. Bits 15 to 12 and 11 to 8 defines the received S1 and S0 tones, see Table 6 and section 1.5.6. Although $C9 holds both Rx data and Rx XTCSS tone information, only one type of signal will be present in the received signal at any one time so no conflict will occur. After receiving a Frame Head the host can read the Address and Size / Information bytes for the following packet from $C5 and optionally the Control byte and the Frame Head Checksum A byte from $C9. The CMX882 will read the Size and Message formatting information and if the message is of type 3, 4 or 5 (see section 1.5.5.4) it will set the automatic decoding of the following data; descrambling, deinterleaving, decoding error correction bytes, stripping out pad bytes, calculating and checking Checksum 2004 CML Microsystems Plc 48 D/882/7 FRS Signalling Processor CMX882 B as required. The only task the host need perform during the reception of formatted Frames is to read out data when it is ready. Note: These 2 words must be read separately. i.e. Two 16 bit C-BUS transactions. 1.6.19 Bit: $CC TONES STATUS: 16-bit read-only 15 14 13 12 11 10 9 8 7 0 6 0 5 4 3 2 1 0 Detected Selcall tone frequency Sub-Audio Status Detected CTCSS code This word holds the current status of the CMX882 sub-audio and In-band tone sections. This word should be read by the host after an interrupt caused by a DCS, CTCSS or In-band tone event. The value in bits 5 to 0, Detected CTCSS code, identifies the detected sub-audio tone by its position in Table 3 CTCSS Tones. If bits 5 to 0 = '000000' there is no CTCSS tone currently being detected. If bits 5 to 0 = '110111' (= 55 in decimal) this indicates that an Invalid Tone has been detected. An Invalid Tone is any tone in the subaudio band which is not the selected subaudio tone nor the all-call tone, or is a tone not listed in Table 3. A change in the state of bits 5-0 to Invalid Tone from the no tone condition will not cause Status register ($C6), b11 to be set to '1'. Any other change in the state of bits 5-0 will cause the Status register ($C6), b11 to be set to '1'. A detected In-band frequency is indicated by the value in bits 15 to 11, `Detected In-band tone frequency', identifies the frequency by its position in Table 6 In-band Tones. If bits 15 to 11 = '00000' there is no In-band tone currently being detected. A change in the state of bits 15 to 11 will cause bit 13 of the Status register ($C6), `In-band State Change', to be set to '1'. Bits 10 to 8 indicate the DCS and special sub-audio tone status. The Status register ($C6) will indicate the type of signal detected. If DCS or special CTCSS tones are detected they will be indicated in bits 10 to 8 according to the table below and bits 7 to 0 will be set to '00000000'. If a normal CTCSS tone is detected bits 10 to 8 will be set to '000' and bits 7 to 0 will indicate the decoded tone. A change in the state of bits 10 to 8 will cause the relevant bit (10 or 11) of the Status register to be set to '1'. Bit 10 0 0 0 0 1 1 1 1 Bit 9 0 0 1 1 0 0 1 1 Bit 8 0 1 0 1 0 1 0 1 Sub-Audio status No DCS or special CTCSS detected Reserved DCS sequence detected inverted DCS sequence detected Reserved 134.4Hz DCS turn off tone detected 64.7Hz XTCSS sub-audio tone detected Reserved Only enabled with DCS Only enabled with DCS Only enabled with DCS Only enabled with XTCSS When the relevant detection mode is not enabled, the associated bits will be set to '0'. In Tx mode this register will be set to '0'. During DCS receive, the device can flag an interrupt when the DCS code fails to be recognised. This may be due to code dropout. The turn off tone may be flagged shortly after, if the transmission is ending. Alternatively the DCS link may be restored and DCS detection will be flagged again. 2004 CML Microsystems Plc 49 D/882/7 FRS Signalling Processor CMX882 1.6.20 Bit: $C8 PROGRAMMING REGISTER: 16-bit write-only 15 First Word 14 Block Num. 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Block Num. or Data Programming Data This register is used for programming various gains, levels, offset compensations, tones and codes. If the user programs any of these values then bit 4 of $C0 (Power Down Control) must be set to '1'. Following a C-BUS Reset or a Power Up Reset, the programmed values are initialised in accordance with the settings described in section 1.6.2 (C-BUS Reset). The Signal Processing function and the XTAL clock circuit must both be enabled in order to write to the Programming Register, so Power Down Control register bit 5 must be set to '1' and bit 3 must be set to '0'. The Programming Register should only be written to when the Programming Flag bit (bit 0) of the Status register is set to '1' and the Rx and Tx modes are disabled (bits 0 and 1 of the Mode Control register both '0'). The Programming Flag is cleared when the Programming Register is written to. When the corresponding programming action has been completed (normally within 250s) the CMX882 will set the flag back to '1' to indicate that it is now safe to write the next programming value. The Programming Register must not be written to while the Programming Flag bit is '0'. Programming is done by writing a sequence of 16-bit words to the Programming Register, in the order shown in the following tables. Writing data to the Programming Register must be performed in the order shown for each of the blocks, however the order in which the blocks are written is not critical. If later words in a block do not require updating the user may stop programming that block when the last change has been performed. e.g. If only 'Fine output gain 1' needs to be changed the host will need to write to P4.0, P4.1 and P4.2 only. The user must not exceed the defined word counts for each block. The word P4.8 is allocated for production testing and must not be accessed in normal operation. The high order bits of each word define which block the word belongs to, and if it is the first word of that block: Bit 15 1 0 X X X X X Bit 14 X X 1 1 1 1 0 Bit 13 X X 0 0 1 1 Bit 12 X X 0 1 0 1 Write to Bit 11 - Bit 0 st 1 data for each block nd 2 and following data Write to block 0 (12 bit words) Write to block 1 (12 bit words) Write to block 2 (12 bit words) Reserved - do not use block 4 (14 bit words) Block 0 - Modem Configuration: Bit: P0.0 P0.1 P0.2 P0.3 P0.4 P0.5 P0.6 P0.7 15 1 0 0 0 0 0 0 0 14 1 1 1 1 1 1 1 1 13 0 0 0 0 0 0 0 0 12 0 0 0 0 0 0 0 0 11 10 0 0 0 0 0 0 0 0 9 8 7 6 5 4 3 2 1 0 MSK Frame Sync LSB MSK Frame Sync MSB Scramble Seed 1 LSB Scramble Seed 1 MSB Scramble Seed 2 LSB Scramble Seed 2 MSB MSK Bit Sync LSB MSK Bit Sync MSB 2004 CML Microsystems Plc 50 D/882/7 FRS Signalling Processor CMX882 Block 1 - XTCSS and In-band tone Setup: Bit: P1.0 P1.1 P1.2 P1.3 P1.4 P1.5 15 1 0 0 0 0 0 14 1 1 1 1 1 1 13 0 0 0 0 0 0 12 1 1 1 1 1 1 XTCSS tone length 0 0 0 0 11 10 9 8 7 6 5 4 3 2 1 0 Emph In-band tone detect bandwidth Audio band Tx level Audio band detect threshold Programmable In-band Tone 0 Programmable In-band Tone 1 Programmable In-band Tone 2 Programmable In-band Tone 3 Block 2 - CTCSS and DCS Setup: Bit: P2.0 P2.1 P2.2 P2.3 P2.4 15 1 0 0 0 0 14 1 1 1 1 1 13 1 1 1 1 1 12 0 0 0 0 0 Sub-audio drop out time DCS 24 11 10 9 8 7 6 5 4 3 2 1 0 CTCSS and DCS Tx level 0 CTCSS and DCS detect threshold DCS Code bits 11 - 0 DCS Code bits 23/22 - 12 0 CTCSS detect bandwidth Block 3 - Reserved. Do not use. Block 4 - Gain and Offset Setup: Bit: P4.0 P4.1 P4.2 P4.3 P4.4 P4.5 P4.6 P4.7 P4.8 15 1 0 0 0 0 0 0 0 0 14 0 0 0 0 0 0 0 0 0 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Fine Input Gain Reserved - set to '0' Fine Output Gain 1 Fine Output Gain 2 Output 1 Offset Control Output 2 Offset Control Ramp Rate Control Limiter Setting (all 1's = Vbias +/- 0.5 Vdd) Special Programming Register (Production Test Only) 2004 CML Microsystems Plc 51 D/882/7 FRS Signalling Processor CMX882 1.6.20.1 PROGRAMMING REGISTER Block 0 - Modem Configuration: $C8 (P0.0-1) Bit: P0.0 P0.1 15 MSK Frame Sync 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 1 0 1 1 0 0 0 0 0 0 MSK Frame Sync LSB MSK Frame Sync MSB Bits 7 to 0 set the Frame Sync pattern used in Tx and Rx MSK data. Bit 7 of the MSB is compared to the earliest received data. After a power on or C-BUS reset they are set to $CB23. $C8 (P0.2-5) Bit: P0.2 P0.3 P0.4 P0.5 15 Scramble Seed 1 and 2 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 0 0 0 0 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 Scramble Seed 1 LSB Scramble Seed 1 MSB Scramble Seed 2 LSB Scramble Seed 2 MSB These bits set the scramble seed used on all data bits following a Frame Head. If $0000 is programmed as the seed then no scrambling will occur when selected. If either programmable scramble seeds are selected, both the transmit and receive devices must use the same seed pattern for data to be transferred correctly. $C8 (P0.6-7) Bit: P0.6 P0.7 15 MSK Bit Sync 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 0 0 1 1 0 0 0 0 0 0 MSK Bit Sync LSB MSK Bit Sync MSB This bit pattern is used when transmitting the bit sync portion of a Frame Head. After a power on or CBUS reset they are set to $5555 (`0101...0101'). 2004 CML Microsystems Plc 52 D/882/7 FRS Signalling Processor CMX882 1.6.20.2 PROGRAMMING REGISTER Block 1 - XTCSS and In-band tone Setup: $C8 (P1.0) Bit: P1.0 15 1 Voice band tones Tx Level 14 1 13 0 12 1 11 10 9 8 7 6 5 4 3 2 1 0 Emph Voice band tones Tx level Bits 11 (MSB) to 1 (LSB) set the transmitted In-band tone, Audio Tone and MSK signal level (pk-pk) with a resolution of VDD(A)/2048 per LSB (1.465mV per LSB at VDD(A)=3V). Valid range for this value is 0 to 1536. Bit 0 controls Rx In-band tone de-emphasis. When set to '0' the signal going to the In-band tone detector is not de-emphasised. When voice processing is enabled in the Mode register, de/pre-emphasis is enabled in the Audio & Device Address register and this bit (b0) is set to '1', signals going to the In-band tone detector are de-emphasised in accordance with Figure 6. $C8 (P1.1) Bit: P1.1 15 0 In-band tone Detect Bandwidth and Audio Band Detect Threshold 14 1 13 0 12 1 11 10 9 8 7 6 5 4 3 2 1 0 XTCSS tone length Audio band detect threshold In-band tone detect bandwidth XTCSS tone length (bits 11 to 10) set the transmit tone length for each of the 4 tones in a XTCSS sequence. In receive these bits define the minimum silent prefix and suffix qualification periods for successful reception, also the maximum receive tone length is double the time set (e.g. for 60ms setting each received tone must be less than 120ms in length for successful XTCSS decoding). '00' = 40ms, '01' = 60ms, '10' = 80ms and '11' = 100ms. The `detect threshold' bits (bits 9 to 4) set the minimum In-band tone and/or MSK signal level that will be detected. The levels are set according to the formula: Minimum Level = Detect Threshold x 3.63mV rms at VDD(A) = 3V The In-band tone detected bandwidth is set in accordance with the following table: Bit 3 1 1 Recommended for EEA 1 1 $C8 (P1.2-5) Bit: P1.2-5 15 0 Bit 2 0 0 0 0 Bit 1 0 0 1 1 Bit 0 0 1 0 1 BANDWIDTH Will Decode Will Not Decode 1.1% 2.4% 1.3% 2.7% 1.6% 2.9% 1.8% 3.2% Programmable In-band Tones 14 1 13 0 12 1 11 0 10 9 8 7 6 5 4 3 2 1 0 Programmable In-band Tone N (see below) R (see below) These words set the programmable In-band tones used in transmit and receive. The frequency is set in bits 10-0 for each word according to the formula: N = Integer part of (0.042666 x frequency) R = (0.042666 x frequency - N) x 6000 / frequency (round to nearest integer) Example: For 1010Hz, N = 43, R = 1. The programmed tones must only be set to frequencies from 400Hz to 3000Hz. 2004 CML Microsystems Plc 53 D/882/7 FRS Signalling Processor CMX882 1.6.20.3 PROGRAMMING REGISTER Block 2 - CTCSS and DCS Setup: $C8 (P2.0) Bit: P2.0 15 1 CTCSS and DCS TX LEVEL 14 1 13 1 12 0 11 10 9 8 7 6 5 4 3 2 1 0 CTCSS and DCS Level Bits 11 (MSB) to 0 (LSB) set the transmitted CTCSS or DCS sub-audio signal level (pk-pk) with a resolution of VDD(A)/16384 per LSB (0.183mV per LSB at VDD(A)=3V, giving a range 0 to 749.8mV pkpk). $C8 (P2.1) Bit: P2.1 15 0 CTCSS TONE BW AND LEVEL 14 1 13 1 12 0 11 DCS 24 10 0 9 8 7 6 5 4 3 2 1 0 CTCSS and DCS detect threshold CTCSS detect bandwidth Bit 11, DCS 24, sets the length of DCS code transmitted or searched for. When this bit is set to `1' 24 bit codes are transmitted and decoded. When this bit is set to `0' 23 bit codes are used. The `detect threshold' bits (bits 9 to 4) set the minimum CTCSS or DCS signal level that will be detected. The levels are set according to the formula: Minimum Level = Detect Threshold x 2mV rms at VDD(A) = 3V The CTCSS detected tone bandwidth is set in accordance with the following table: Bit 3 Recommended for use with split tones Recommended for CTCSS 0 0 1 1 1 1 Bit 2 1 1 0 0 0 0 Bit 1 1 1 0 0 1 1 Bit 0 0 1 0 1 0 1 BANDWIDTH Will Decode Will Not Decode 0.5% 0.8% 1.1% 1.3% 1.6% 1.8% 1.8% 2.1% 2.4% 2.7% 2.9% 3.2% $C8 (P2.2-3) Bit: P2.2 P2.3 15 0 0 DCS CODE (LOWER) and DCS CODE (UPPER) 14 1 1 13 1 1 12 0 0 11 10 9 8 7 6 5 4 3 2 1 0 DCS Data (bits 11-0) DCS Data (bits 23/22-12) These words set the DCS code to be transmitted or searched for. The least significant bit (bit 0) of the DCS code is transmitted or compared first and the most significant bit is transmitted or compared last. Note that DCS Data bit 23 is only used when bit 11 (DCS 24) of P2.1 is set to `1'. $C8 (P2.4) Bit: P2.4 15 0 SUBAUDIO DROP OUT TIME 14 1 13 1 12 0 11 10 9 8 7 6 5 4 0 3 2 1 0 Subaudio Drop Out Time The Subaudio Drop Out Time defines the time that the sub-audio signal detection can drop out before loss of sub-audio is asserted. The period is set according to the formula: Time = Subaudio Drop Out Time x 8.0ms [range 0 to 120ms] The setting of this register defines the maximum drop out time that the device can tolerate. The setting of this register also determines the de-response time, which is typically 40ms longer than the programmed drop out time. 2004 CML Microsystems Plc 54 D/882/7 FRS Signalling Processor CMX882 1.6.20.4 PROGRAMMING REGISTER Block 3 - Reserved 1.6.20.5 PROGRAMMING REGISTER Block 4 - Gain and Offset Setup $C8 (P4.0) Bit: P4.0 15 1 FINE INPUT GAIN 14 0 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Fine Input Gain (unsigned integer) Gain = 20 x log([32768-IG]/32768) IG is the unsigned integer value in the `Fine Input Gain' field Fine input gain adjustment should be kept within the range 0 to -3.5dB. $C8 (P4.1) Bit: P4.1 15 0 Reserved 14 0 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Reserved - set to '0' This register is reserved and should be set to '0'. $C8 (P4.2-3) Bit: P4.2 P4.3 15 0 0 FINE OUTPUT GAIN 1 and FINE OUTPUT GAIN 2 14 0 0 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Fine Output Gain 1 (unsigned integer) Fine Output Gain 2 (unsigned integer) Gain = 20 x log([32768-OG]/32768) OG is the unsigned integer value in the `Fine Output Gain' field Fine output gain adjustment should be kept within the range 0dB to -3.5dB. $C8 (P4.4-5) Bit: P4.4 P4.5 15 0 0 OUTPUT 1 OFFSET and OUTPUT 2 OFFSET 14 0 0 13 12 11 10 9 8 7 6 5 4 3 2 1 0 2's complement offset for MOD_1, resolution = VDD(A)/16384 per LSB 2's complement offset for MOD_2, resolution = VDD(A)/16384 per LSB Can be used to compensate for inherent offsets in the output path via MOD_1 (Output 1 Offset) and MOD_2 (Output 2 Offset). It is recommended that the offset correction is kept within the range +/-50mV. $C8 (P4.6) Bit: P4.6 15 0 RAMP RATE CONTROL 14 0 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Ramp Rate Up Control (RRU) Ramp Rate Down control (RRD) The ramp-up and ramp-down rates can be independently programmed. The ramp rates apply to all the analogue output ports. They only affect those ports being turned on (ramp-up) or turned off (ramp down). The ramp rates should be programmed before ramping any outputs. Time to ramp-up to full gain = Time to ramp down to zero gain = (1 + RRU) x 1.333ms (1 + RRD) x 1.333ms 2004 CML Microsystems Plc 55 D/882/7 FRS Signalling Processor CMX882 $C8 (P4.7) Bit: P4.7 15 0 TRANSMIT LIMITER CONTROL 14 0 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Limiter Setting, resolution = VDD(A)/16384 per LSB This unsigned number sets the clipping point (maximum deviation from the centre value) for the MOD_1 and MOD_2 pins. The maximum setting ($2000) is +/- VDD(A)/2 i.e. output limited from 0 to VDD(A). Any settings above $2000 will limit to the $2000 setting. The limiter is set to maximum following a C-BUS Reset or a Power Up Reset. The limiter is only applied to voice signals, not internally generated audio band signals. The levels of internally generated signals must be limited by setting appropriate transmit levels. $C8 (P4.8) Special Programming Register - do not access. 2004 CML Microsystems Plc 56 D/882/7 FRS Signalling Processor CMX882 1.7 Application Notes R a dio S e ction Rx D e m od u la to r RF 2-p oin t T x M o du lator D iscrim in ato r inp ut R eceive F FS K V oice+ SubA udio A udio ou tpu t M od ula tor ou tpu t 1 CM X882 T ransm it A udio inpu t 1 M od ula tor ou tpu t 2 M IC 1 F FS K V oice+ SubA udio A udio inpu t 2 M IC 2 C -B U S D isp lay GPS H o st M icro C o ntro lle r K e yp ad Figure 13 Possible FRS + GPS Configuration 1.7.1 CRC and FEC encoding information Data bits 4 3 0 1 1 0 1 1 1 0 FEC bits 2 1 0 0 1 0 0 1 0 0 For messages with FEC coding the following matrix is used to calculate and decode bytes: 7 1 1 1 0 6 1 1 0 1 5 1 0 1 1 2 1 0 0 1 1 0 1 1 0 0 0 1 0 1 3 1 0 0 0 0 0 0 0 1 8 bit CRC is used in all frame heads with the following generator polynomial (GP): x +x +x +x +x +x 8 7 4 3 1 0 16 bit CRC is used at the end of sized data messages of up to 16 bytes with the following GP: x 16 +x 12 +x +x 5 0 32 bit CRC is used at the end of sized data messages of over 16 bytes with the following GP: x 32 +x 31 +x 30 +x 28 +x 27 +x 25 +x 24 +x 22 +x 21 +x 20 +x 16 +x 10 +x +x +x 9 6 0 The scrambler uses a 16 bit pseudo random number generator with the following feed back taps: x 16 +x 14 +x +x 1 0 2004 CML Microsystems Plc 57 D/882/7 FRS Signalling Processor CMX882 1.7.2 Data Interleaving The built in FFSK packeting includes the option of interleaving the data in each block (Type 5). This, together with Forward Error Correction (FEC), reduces the effects of one of the commonest sources of data errors which is burst noise. Interleaving does not add any bits to the message, the packet is assembled in 'rows' and then transmitting in 'columns'. 0 12 24 36 1 13 25 37 2 14 26 38 Data (8 bits) 3 4 5 15 16 17 27 28 29 39 40 41 6 18 30 42 7 19 31 43 8 20 32 44 FEC (4 bits) 9 10 21 22 33 34 45 46 11 23 35 47 In the above example the packet is assembled as 4 rows with 12 bits of information per row. When this packet is transmitted interleaved the bits are sent over the communication channel in the following order: 0, 12, 24, 36, 1, 13, 25, 37, 2, 14, ... , 33, 45, 10, 22, 34, 46, 11, 23, 35, 47. In the receiving modem the packet is re-assembled (de-interleaved) before error correction. The 882's built in packet receive modem is able to recognise (by using the frame head bytes) when the data has been interleaved by the transmitter and will decode the data using the correct method. 1.7.3 Scrambler Seed Transfer The CMX882 data scrambler provides some security for information transfer by allowing the use of different seed patterns. This requires that the transmitting and receiving devices have identical scrambler seeds. Should two radios wish to transfer data using the scrambler the seed must be transferred between them before data transfer takes place. This is best done 'off air' by prior arrangement. Obviously sending the seed over air by voice or by using FFSK (with either no scrambling or the standard scrambler) will enable an eavesdropper to grab the seed as it is transferred and then decode any following messages using that seed. The following method allows the transfer of a seed between two unrelated radios (from A to B) without the actual 16 bit seed pattern appearing over the air: Radio A B A B Calculates Seed + X Rx + Y Rx - X Rx - Y Sends over air Seed + X Seed + X + Y Seed + Y Example (4 bit), X=3, Y=9 Calculates Sends over air 11 8+3 11 + 9 4 4-3 1 1-9=8 The values used for the Seed, X and Y can be any number up to 65535 and all 3 numbers should be different for each seed transfer. This and other simple methods allow an eavesdropper to use basic mathematical techniques (11-4+1 in the above example) to use the over air information to derive the original seed (they must however have detected all three over air messages to do this). To reduce this possibility the host can employ more sophisticated techniques for seed transfer (e.g. functions using large prime numbers) as this will greatly increase the mathematical complexity required to find the original seed. However such methods are; beyond the scope of this document, may not be permitted in certain territories and probably not appropriate for the level of security provided by the inbuilt scrambler. 2004 CML Microsystems Plc 58 D/882/7 FRS Signalling Processor CMX882 1.8 Performance Specification 1.8.1 Electrical Performance The performance data are target figures, that may change subject to the outcome of device evaluation. Absolute Maximum Ratings Exceeding these maximum ratings can result in damage to the device. Min. -0.3 -0.3 -0.3 -0.3 -30 -20 0 0 Max. 7.0 7.0 VDD(D) + 0.3 VDD(A) + 0.3 +30 +20 0.3 50 Unit V V V V mA mA V mV Supply: VDD(D)- VSS(D) VDD(A)- VSS(A) Voltage on any pin to VSS(D) Voltage on any pin to VSS(A) Current into or out of VDD(A), VSS(A), VDD(D) and VSS(D) Current into or out of any other pin Voltage differential between power supplies: VDD(D) and VDD(A) VSS(D) and VSS(A) D6 Package (SSOP) Total Allowable Power Dissipation at Tamb = 25C ... Derating Storage Temperature Operating Temperature Min. -55 -40 Min. -55 -40 Max. 550 9 +125 +85 Unit mW mW/C C C E1 Package (TSSOP) Total Allowable Power Dissipation at Tamb = 25C ... Derating Storage Temperature Operating Temperature Max. 400 5.3 +125 +85 Unit mW mW/C C C Operating Limits Correct operation of the device outside these limits is not implied. Notes Supply (VDD - VSS) Operating Temperature Clock/Xtal Frequency Notes: 11 11 Min. 2.7 -40 18.3 Max. 3.6 +85 18.6 Unit V C MHz Nominal clock frequency is 18.432MHz. 2004 CML Microsystems Plc 59 D/882/7 FRS Signalling Processor CMX882 Operating Characteristics For the following conditions unless otherwise specified: External components as recommended in Figure 2. Maximum load on digital outputs = 30pF. Xtal Frequency = 18.432MHz 0.01% (100ppm). VDD = 2.7V to 3.6V; Tamb = -40C to +85C. Reference Signal Level = 308mV rms at 1kHz with VDD = 3V. Signal to Noise Ratio (SNR) in bit rate bandwidth. Input stage gain = 0dB. Output stage attenuation = 0dB. DC Parameters Supply Current IDD(D) (VDD = 3.0V) IDD(A) (VDD = 3.0V) IDD(D) (All Power-saved) (VDD = 3.0V) IDD(A) (All Power-saved) (VDD = 3.0V) C-BUS Interface Input Logic `1' Input Logic `0' Input Leakage Current (Logic `1' or `0') Input Capacitance Output Logic `1' (IOH = 120A) Output Logic `0' (IOL = 360A) "Off" State Leakage Current IRQN (Vout = VDD(D)) REPLY_DATA (output HiZ) CLOCK_OUT Output Logic `1' Output Logic `0' CLOCK/XTAL Input Logic `1' Input Logic `0' Input current (Vin = VDD) Input current (Vin = VSS) VBIAS Output voltage offset wrt VDD/2 (IOL < 1A) Output impedance Notes: 21 22 23 (IOH = 120A) (IOH = 1mA) (IOL = 360A) (IOL = -1.5mA) 22 70% -40 23 -2% 22 +2% VDD k 30% 40 VDD VDD A A Notes 21 21 21 21 70% -1.0 90% -1.0 -1.0 90% 80% 10% 15% 30% 1.0 7.5 10% 10 1.0 1.0 Min. Typ. 4.5 1.0 2.0 2.0 Max. 8.0 2.0 10 10 Unit mA mA A A VDD VDD A pF VDD VDD A A A VDD VDD VDD VDD Not including any current drawn from the device pins by external circuitry. Characteristics when driving the CLOCK/XTAL pin with an external clock source. Applies when utilising VBIAS to provide a reference voltage to other parts of the system. When using VBIAS as a reference, VBIAS must be buffered. VBIAS must always be decoupled with a capacitor as shown in Figure 2. 2004 CML Microsystems Plc 60 D/882/7 FRS Signalling Processor CMX882 AC Parameters CLOCK/XTAL Input 'High' pulse width 'Low' pulse width Input impedance (at 18.432MHz) Powered-up Resistance Capacitance Powered-down Resistance Capacitance Clock frequency Clock stability/accuracy Clock start up (from power-save) CLOCK_OUT Output CLOCK/XTAL input to CLOCK_OUT timing: (in high to out high) (in low to out low) 'High' pulse width 'Low' pulse width VBIAS Start up time (from power-save) Microphone, Input_2 and Disc Inputs (MIC, INPUT_2, DISC) Input impedance Input signal range Load resistance (pin 12, 14 and 16) Amplifier open loop voltage gain (I/P = 1mV rms at 100Hz) Unity gain bandwidth Programmable Input Gain Stage Gain (at 0dB) Cumulative Gain Error (wrt attenuation at 0dB) Notes: 31 32 33 34 35 36 Notes 31 31 Min. 21 21 Typ. Max. Unit ns ns 150 20 300 20 18.432 100 400 k pF k pF MHz ppm ms 32 32 33 33 22 22 15 15 27.13 27.13 30 33 33 ns ns ns ns ms 34 35 1 10 80 60 1.0 90 M %VDD k dB MHz 36 -0.5 -1.0 0 0.5 1.0 dB dB Timing for an external input to the CLOCK/XTAL pin. CLOCK/XTAL input driven by external source. 18.432MHz XTAL fitted. With no external components connected After multiplying by gain of input circuit, with external components connected. Gain applied to signal at output of buffer amplifier, pin 12, 14 or 16 2004 CML Microsystems Plc 61 D/882/7 FRS Signalling Processor CMX882 AC Parameters Modulator Outputs 1 and 2 and Audio Output (MOD_1, MOD_2, AUDIO) Power-up to output stable Modulator Attenuators Attenuation (at 0dB) Cumulative Attenuation Error (wrt attenuation at 0dB) Output Impedance Enabled Disabled Audio Attenuator Attenuation (at 0dB) Cumulative Attenuation Error (wrt attenuation at 0dB) Output Impedance Enabled Disabled Feedback load resistance Amplifier open loop voltage gain (I/P = 1mV rms at 100Hz) Unity gain bandwidth Notes: 37 Notes Min. Typ. Max. Unit 37 -0.2 -0.6 38 38 -0.5 -1.0 38 38 80 50 0 100 0.2 0.6 s dB dB k dB dB k k dB MHz 600 500 0 0.5 1.0 600 500 60 1.0 38 Power-up refers to issuing a C-BUS command to turn on an output. These limits apply only if VBIAS is on and stable. At power supply switch-on, the default state is for all blocks, except the XTAL and C-BUS interface, to be in placed in powersave mode. Small signal impedance, at VDD = 3.0V and Tamb = 25C. 2004 CML Microsystems Plc 62 D/882/7 FRS Signalling Processor CMX882 AC Parameters (cont.) Auxiliary ADC (Signal Monitor) 8 Bit ADC Mode Resolution Input Range Conversion time Input impedance Resistance Capacitance Zero error (input offset to give ADC output = 0) Integral Non-linearity Differential Non-linearity Source output impedance Level Threshold Detect Mode Threshold Resolution Upper threshold range (VTH) Lower threshold range (VTL) Signal Monitor change to IRQ Signal Monitor change to Receiver-Turn-On Audio Compandor Attack time Decay time 0dB point Compression / Expansion ratio Notes: 41 42 43 44 45 46 47 48 Notes Min. Typ. Max. Unit 8 10% 41 20.8 10 5 -20 42 43 42 43 44 8 45 45 46 47 VTL VSS(A) VDD(A) VTH 120 60 4.0 13 100 2:1 +20 2 4 1 3 24 90% Bits VDD s M pF mV LSB LSB LSB LSB k Bits V V s s ms ms mVrms 48 With clock frequency of 18.432MHz. VDD(A) 3.0V VDD(A) < 3.0V Denotes output impedance of the driver of the Signal Monitor input, to ensure < 1 bit additional error under nominal conditions. Upper threshold > Lower threshold Time from Signal Monitor input rising above Upper Threshold or falling below Lower Threshold, to IRQN being asserted. Time from Signal Monitor input rising above Upper Threshold to receiver path powering up, settling and starting automatic signal type identification. VDD(A) = 3.0V 2004 CML Microsystems Plc 63 D/882/7 FRS Signalling Processor CMX882 AC Parameters (cont.) Receiver Signal Type Identification Probability of correctly identifying signal type (SNR = 12dB) CTCSS Detector Sensitivity Response Time De-response Time Dropout immunity Frequency Range IN-BAND TONE Detector Sensitivity Response Time De-response Time Dropout immunity Frequency Range DCS Decoder Sensitivity Bit-Rate Sync Time FFSK/MSK Decoder Signal Input Dynamic Range Bit Error Rate (SNR = 20dB) Receiver Synchronisation (SNR = 12dB) Probability of bit 16 being correct (Pure Tone) (Composite Signal) (Composite Signal) Notes Min. Typ. Max. Unit >>99.9 51 52 52, 55 55 60 -26 140 210 160 % dB ms ms ms Hz dB ms ms ms Hz mVp-p edges 800 mVrms -8 10 % 250 260 (Pure Tone) (Good Signal) (Good Signal) (In-band tone) 53 -26 35 400 45 20 3000 51 58 2 54 54 100 <1 >99.9 Notes: 51 52 53 54 55 Sub-Audio Detection Level threshold set to 16mV. Composite signal = 308mV rms at 1kHz + 75mV rms Noise + 31mV rms SubAudio signal. Noise bandwidth = 5kHz Band Limited Gaussian. In-band Tone Detection Level threshold set to 16mV. VDD(A) = 3.0V, for a "101010101 ... 01" pattern measured at the input amplifier feedback pin (12). Signal level scales with VDD(A). See Figure 15 for variation of BER with SNR. With sub-audio dropout time (P2.4) set to 120ms. The typical dropout immunity is approximately 40ms more than the programmed dropout immunity. The typical de-response time is approximately 90ms longer than the programmed dropout immunity. See section 1.6.20.3, P2.4. 2004 CML Microsystems Plc 64 D/882/7 FRS Signalling Processor CMX882 AC Parameters (cont.) CTCSS Encoder Frequency Range Tone Frequency Accuracy Tone Amplitude Tolerance Total Harmonic Distortion In-band tone Encoder Frequency Range Tone Frequency Accuracy Tone Amplitude Tolerance Total Harmonic Distortion DCS Encoder Bit Rate Amplitude Tolerance FFSK/MSK Encoder Output signal level Output level variation Output distortion rd 3 harmonic distortion Logic 1 freq 1200baud and 2400baud Logic 0 freq 1200baud 2400baud Isochronous distortion (0 to 1 and 1 to 0) Notes Min. 60.0 Typ. Max. 260 0.3 +1.0 4.0 3000 0.3 +1.0 4.0 Unit Hz % dB % Hz % dB % bits/s dB mVrms dB % % Hz Hz Hz s 61 62 -1.0 2.0 400 63 62 -1.0 2.0 134.4 61 -1.0 775 -1.0 1198 1798 2398 1200 1800 2400 +1.0 +1.0 5 3 1202 1802 2402 40 Notes: 61 62 63 VDD(A) = 3.0V and TX Sub-Audio Level set to 88mV p-p (31mV rms). Measured at MOD_1 or MOD_2 output. VDD(A) = 3.0V and Tx Audio Level set to 871mV p-p (308mV rms). 2004 CML Microsystems Plc 65 D/882/7 FRS Signalling Processor CMX882 AC Parameters (cont.) Analogue Channel Audio Filtering Pass-band (nominal bandwidth): Received voice 12.5kHz channel transmitted voice 25kHz channel transmitted voice Pass-band Gain (at 1.0kHz) Pass-band Ripple (wrt gain at 1.0kHz) Stop-band Attenuation Residual Hum and Noise Pre-emphasis De-emphasis Audio Scrambler Inversion frequency Pass band Notes: 71 72 73 74 75 76 Notes Min. Typ. Max. Unit 71 72 73 300 300 300 0 -2 33.0 3000 2550 3000 +0.5 -50 6 -6 3300 76 74 75 300 Hz Hz Hz dB dB dB dBp dB/oct dB/oct 3000 Hz Hz The receiver voice filter complies with the characteristic shown in Figure 5. The high pass filtering removes sub-audio components from the audio signal. The 12.5kHz channel filter complies with the characteristic shown in Figure 9. The 25kHz channel filter complies with the characteristic shown in Figure 8. The pre-emphasis filter complies with the characteristic shown in Figure 10. The de-emphasis filter complies with the characteristic shown in Figure 6. dBp represents a psophometrically weighted measurement. 2004 CML Microsystems Plc 66 D/882/7 FRS Signalling Processor CMX882 C-BUS Timing Figure 14 C-BUS Timing C-BUS Timing tCSE CSN Enable to SClk high time tCSH Last SClk high to CSN high time SClk low to ReplyData Output Enable tLOZ Time tHIZ CSN high to ReplyData high impedance CSN high time between transactions tCSOFF Inter-byte time tNXT SClk cycle time tCK SClk high time tCH SClk low time tCL Command Data setup time tCDS Command Data hold time tCDH Reply Data setup time tRDS Reply Data hold time tRDH Notes: Notes Min. 100 100 0.0 1.0 200 200 100 100 75 25 50 0 Typ. Max. Unit ns ns ns s s ns ns ns ns ns ns ns ns 1.0 1. Depending on the command, 1 or 2 bytes of COMMAND DATA are transmitted to the peripheral MSB (Bit 7) first, LSB (Bit 0) last. REPLY DATA is read from the peripheral MSB (Bit 7) first, LSB (Bit 0) last. 2. Data is clocked into the peripheral on the rising SERIAL_CLOCK edge. 3. Commands are acted upon at the end of each command (rising edge of CSN). 4. To allow for differing C serial interface formats C-BUS compatible ICs are able to work with SERIAL_CLOCK pulses starting and ending at either polarity. 5. Maximum 30pF load on IRQN pin and each C-BUS interface line. These timings are for the latest version of C-BUS and allow faster transfers than the original C-BUS timing specification. The CMX882 can be used in conjunction with devices that comply with the slower timings, subject to system throughput constraints. 2004 CML Microsystems Plc 67 D/882/7 FRS Signalling Processor CMX882 1.0E-01 1.0E-02 1.0E-03 2400 b/s 1.0E-04 1200 b/s 1.0E-05 4 5 6 7 8 9 10 11 12 13 14 SNR (dB) - Noise in bit rate bandwidth Figure 15 Typical FFSK/MSK Bit Error Rate Graph 2004 CML Microsystems Plc 68 D/882/7 FRS Signalling Processor CMX882 1.8.2 Packaging Figure 16 Mechanical Outline of 28-pin SSOP (D6): Order as part no. CMX882D6 Figure 17 Mechanical Outline of 28-pin TSSOP (E1): Order as part no. CMX882E1 2004 CML Microsystems Plc 69 D/882/7 FRS Signalling Processor CMX882 Handling precautions: This product includes input protection, however, precautions should be taken to prevent device damage from electro-static discharge. CML does not assume any responsibility for the use of any circuitry described. No IPR or circuit patent licences are implied. CML reserves the right at any time without notice to change the said circuitry and this product specification. CML has a policy of testing every product shipped using calibrated test equipment to ensure compliance with this product specification. Specific testing of all circuit parameters is not necessarily performed. www.cmlmicro.com For FAQs see: www.cmlmicro.com/products/faqs/ For a full data sheet listing see: www.cmlmicro.com/products/datasheets/download.htm For detailed application notes: www.cmlmicro.com/products/applications/ Oval Park, Langford, Maldon, Essex, CM9 6WG - England. 4800 Bethania Station Road, Winston-Salem, NC 27105 - USA. No 2 Kallang Pudding Road, #09 to 05/06 Mactech Industrial Building, Singapore 349307 No. 218, Tian Mu Road West, Tower 1, Unit 1008, Shanghai Kerry Everbright City, Zhabei, Shanghai 200070, China. Tel: +86 21 6317 4107 +86 21 6317 8916 Fax: +86 21 6317 0243 Sales: cn.sales@cmlmicro.com.cn Technical Support: sg.techsupport@cmlmicro.com Tel: +44 (0)1621 875500 Fax: +44 (0)1621 875600 Sales: sales@cmlmicro.com Technical Support: techsupport@cmlmicro.com Tel: +1 336 744 5050, 800 638 5577 Fax: +1 336 744 5054 Sales: us.sales@cmlmicro.com Technical Support: us.techsupport@cmlmicro.com Tel: +65 6745 0426 Fax: +65 6745 2917 Sales: sg.sales@cmlmicro.com Technical Support: sg.techsupport@cmlmicro.com |
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