CMX138 CML Microcircuits, CMX138 Datasheet
CMX138
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CMX138 Summary of contents
Page 1
... Reference Clock 1 Brief Description The CMX138 is a half-duplex, audio scrambler and sub-audio signalling processor IC for Analogue Two- Way Radio applications. This makes it a suitable device for the leisure radio markets (FRS, MURS, PMR446 and GMRS). This device provides a user programmable frequency inversion audio scrambler, companding and pre/de- emphasis – ...
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... Digital System Clock Generator ................................................................................32 7.9.1 Main Clock Operation ..........................................................................................32 7.9.2 System Clock Operation......................................................................................33 7.10 GPIO..........................................................................................................................34 7.11 Signal Level Optimisation ..........................................................................................34 7.11.1 Transmit Path Levels ..........................................................................................34 7.11.2 Receive Path Levels ...........................................................................................34 8 C-BUS Register Summary ...................................................................................................35 8.1.1 Interrupt Operation ..............................................................................................36 8.1.2 General Notes .....................................................................................................36 9 Configuration Guide.............................................................................................................37 9.1 C-BUS Register Details.............................................................................................37 © 2008 CML Microsystems Plc CONTENTS Page 2 CMX138 Page D/138_FI1.0/5 ...
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... Operating Limits..................................................................................................61 11.1.3 Operating Characteristics ...................................................................................62 11.1.4 Parametric Performance .....................................................................................67 11.2 C-BUS Timing............................................................................................................70 11.3 Packaging..................................................................................................................71 Table Table 1 Xtal/clock frequency settings for Program Block 3 .......................................................... 13 Table 2 DCS Codes and CTCSS Tones........................................................................................ 25 Table 3 DCS Modulation Modes ................................................................................................... 27 Table 4 DCS 23 Bit Codes............................................................................................................ 28 © 2008 CML Microsystems Plc Page 3 CMX138 Page D/138_FI1.0/5 ...
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... Table 7 Reset Operations ............................................................................................................. 38 Table 8 RAMDAC Values ............................................................................................................. 55 Figure Figure 1 Block Diagram .................................................................................................................. 6 Figure 2 CMX138 Recommended External Components .............................................................. 9 Figure 3 CMX138 Power Supply Connections and De-coupling.................................................. 11 Figure 4 C-BUS Transactions ....................................................................................................... 14 Figure 5 Signal Routing ................................................................................................................ 15 Figure 6 Rx 25kHz Channel Audio Filter Frequency Response................................................... 18 Figure 7 De-emphasis Curve for TIA/EIA-603 Compliance.......................................................... 18 Figure 8 Tx Channel Audio Filter Response and Template (ETSI) ...
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... Additional explanation about use of the CLKSEL pin in Signal List and Table 1. 5 Add explanation of the initial value for ADC averaging. Add note 99 to define conditions for scrambler audio pass-band measurement. Clarify the polarity of DCS Rx and Tx signals in sections 7.5.2 and 7.5.4 © 2008 CML Microsystems Plc Page 5 CMX138 Date 12/2/08 23/4/08 D/138_FI1.0/5 ...
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... Figure 1 Block Diagram Page 6 Mux Soft Channel Limiter Filter Expander sw (Optional) Auxiliary Functions Auxiliary System Clocks Programmable PLL Clock I/O configuration I/O Auxiliary DAC Ramp profile RAM DAC 1 Auxiliary ADC Thresholds ADC sw Averaging CMX138 MOD AUDIO Clock O/P Tx Enable Rx Enable Clock Select DAC O/P ADC I/P D/138_FI1.0/5 ...
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... DISC inverting input 2. IP DISC inverting input 1. OP DISC input amplifier feedback. OP Audio output. PWR Analog Ground. OP Auxiliary DAC output / RAMDAC. PWR Digital Ground. Page 7 Description by capacitors mounted close to the device SS /2, except when the device DD will discharge Must be BIAS SS CMX138 D/138_FI1.0/5 ...
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... Input (+ PU/PD = internal pullup/pulldown resistor) Notes Output BI = Bidirectional 3-state Output PWR = Power Connection Connection - should NOT be connected to any signal. © 2008 CML Microsystems Plc Type IP+PU Clock Speed Select (hi = 6.144 3.6864MHz). OP Digital Output pin – RxENA (active lo). Page 8 Description D/138_FI1.0/5 CMX138 ...
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... Audio Scrambler and Sub-Audio Signalling Processor 5 External Components TxENA C14 C15 SYSCLK R10 RDATA CDATA DV C10 C13 C12 C11 C9 DVss R9 C8 MICFB AV SS Figure 2 CMX138 Recommended External Components R1 TBD 100kΩ R3 R10 100kΩ R4 R11 100kΩ R5 R12 100kΩ R6 100kΩ R7 100kΩ ...
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... If the MIC input is AC coupled, the selection of the coupling capacitor should allow for frequencies from 300Hz and up to 3kHz to be passed without significant distortion to allow the audio filtering and processing to function within their specification. © 2008 CML Microsystems Plc For optimum performance with low signal microphones, an Page 10 CMX138 and R5 deleted. BIAS D/138_FI1.0/5 ...
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... It is therefore recommended that the printed circuit board is laid out with separate ground planes for the AV the CMX138, with provision to make links between them, close to the device. Use of a multi-layer printed circuit board will facilitate the provision of ground planes on separate layers. ...
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... Audio Scrambler and Sub-Audio Signalling Processor 6 General Description The CMX138 is intended for use in half duplex analogue two way mobile radio or family radio equipment and is particularly suited to enhanced MURS / GMRS / FRS designs. The CMX138 provides a user programmable frequency inversion audio scrambler integrated with signal processing functions, CTCSS, DCS and in-band tones, permitting sophisticated levels of tone control and voice processing ...
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... CMX138’s Read Only Registers, as illustrated in Figure 4. Data sent from the µC on the Command Data line is clocked into the CMX138 on the rising edge of the Serial Clock input. Reply Data sent from the CMX138 to the µC is valid when the Serial Clock is high. ...
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... For detailed timings see section 11.2. Note that, due to internal timing constraints, there may be a delay 250μs between the end of a C-BUS write operation and the CMX138 responding to the C-BUS command. C-BUS Write: ...
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... Device Control CMX138 can be set into many modes to suit the environment in which used. These modes are described in the following sections and are programmed over the C-BUS: either directly to operational registers or, for parameters that are not likely to change during operation, via the Programming register ($C8) ...
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... Programming registers. See: Analogue Input Gain - $B0 write o Analogue Output Gain - $B1 write o 7.3.2 Mode Control The CMX138 operates in one of three modes: IDLE power-on or following a Reset, the device will automatically enter IDLE mode, which allows for the maximum powersaving whilst still retaining the capability of monitoring the AuxADC inputs (if enabled) ...
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... Audio Receive Mode The CMX138 operates in half duplex, so whilst in receive mode the transmit path (microphone input and modulator output amplifiers) can be disabled and powered down. The AUDIO output signal level is equalised ( before switching between the audio port and the modulator ports, to minimise BIAS unwanted audible transients ...
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... Figure 6 Rx 25kHz Channel Audio Filter Frequency Response de-emp & 12.5k - $3000 de-emp & 12.5k & hpf - $3400 template -10 -15 -20 -25 -30 -35 -40 Figure 7 De-emphasis Curve for TIA/EIA-603 Compliance © 2008 CML Microsystems Plc frequency (Hz) frequency (Hz) Page 18 CMX138 D/138_FI1.0/5 ...
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... For all transmissions, the host µC 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 CMX138 will use the settings to control the way information is transmitted. ...
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... Figure 8 Tx Channel Audio Filter Response and Template (ETSI) Tx all filters off - $0000 hpf & 12.5k filter - $1400 template 25k filter - $0800 -10 -15 -20 -25 -30 -35 -40 Figure 9 Tx Channel Audio Filter Response and Template (TIA) © 2008 CML Microsystems Plc frequency (Hz) frequency (Hz) Page 20 CMX138 D/138_FI1.0/5 ...
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... Audio Control – $C2 write o Audio Scrambling The CMX138 incorporates an optional frequency inversion scrambler in transmit and receive modes. This scrambles transmitted audio band signals, which can then be de-scrambled in the receiver. The inversion frequency can be programmed using the Scramble Frequency register, $CB. The default value is 3300Hz. ...
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... The CMX138 uses a “syllabic compandor.” This type of compandor, as opposed to the instantaneous compandor (e.g. µ/A-law PCM), responds to changes in the average envelope of the signal amplitude according to a syllabic time constant τ ...
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... Audio Scrambler and Sub-Audio Signalling Processor Figure 12 Compressor Transient Response © 2008 CML Microsystems Plc Page 23 CMX138 D/138_FI1.0/5 ...
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... Tone Clone™ mode which will report back any received CTCSS tone rather than look for a specific tone. There are 51 CTCSS tones defined in the CMX138 and there is provision for a user-specified tone. Tone phase adjustment (180 or 120 degrees) to implement “Reverse Tone Burst” for squelch tail elimination can be accomplished by setting b9 the Audio Control register, $C2 ...
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... lid D/138_FI1.0/5 CMX138 ...
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... Receiving and Decoding CTCSS Tones The CMX138 is able to accurately detect valid CTCSS tones quickly to avoid losing the beginning of audio or 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 13, to prevent signals outside the sub-audio range from interfering with the sub-audio tone detection ...
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... Receiving and Decoding DCS Codes DCS code is in NRZ format and transmitted at 134.4±0.4bps. The CMX138 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 3. The CMX138 can detect a valid DCS code quickly enough to avoid losing the beginning of audio transmissions ...
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... The end of DCS transmissions is indicated by a 134.4 ±0.5Hz tone for 150-200ms. When a valid DCS code has been detected, the CMX138 will automatically scan for the turn-off tone. When the DCS turn-off tone is detected it will cause a DCS interrupt and report tone 54 (Tone Status b0-7 value 254 decimal); ...
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... HPF disabled. By default, the CMX138 will use a 1750Hz tone, however this may be changed by the host to any valid tone within its operational range by use of the Programming register. This ensures that the device can remain compatible with all available tone systems in use ...
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... Note that the thresholds are inverted due to the op-amp on the AuxADC input pin. © 2008 CML Microsystems Plc Table 5 In-band Tone b11 Rx Mode $ tone 0 Tone Detected 1 Unrecognised Tone Page 30 CMX138 Tx Mode $C3 No tone Transmit In-band Tone reserved D/138_FI1.0/5 ...
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... The AuxDAC output holds the user-programmed level during a powersave operation if left enabled, otherwise it will return to zero. See: AuxDAC control / data - $A8 write o © 2008 CML Microsystems Plc Figure 14 AuxADC IRQ operation Page 31 CMX138 D/138_FI1.0/5 ...
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... Main Clock Operation A PLL is used to create the Main Clock (nominally 24.576MHz) for the internal sections of the CMX138. At the same time, other internal clocks are generated by division of either the XTAL Reference Clock or the Main Clock. These internal clocks are used for determining the sample rates and conversion times of A-to-D and D-to-A converters, running a General Purpose Timer and the signal processing block ...
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... If not required, this clock can be independently powersaved. The clock generation scheme is shown in the block diagram of Figure 15. Note that at power-on the System Clock output is turned off and the output is held at '0'. See: System CLK 1 PLL data - $AB write o System CLK 1 REF - $AC write o © 2008 CML Microsystems Plc Page 33 CMX138 D/138_FI1.0/5 ...
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... Audio Scrambler and Sub-Audio Signalling Processor 7.10 GPIO Two pins on the CMX138 are provided for Rx and Tx Enables. These pins become active low when the device enters the appropriate mode. These can be used for driving external circuitry and have the advantage of having minimal delay from the activation of the selected mode and so are not dependant upon any delays due to the transfer of commands / data over the C-BUS ...
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... All other C-BUS addresses (including those not listed above) are either reserved for future use or allocated for production testing and must not be accessed in normal operation. © 2008 CML Microsystems Plc Table 6 C-BUS Registers REGISTER C-BUS RESET Page 35 CMX138 Word Size (bits ...
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... Interrupt Operation The CMX138 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 and the corresponding mask bit(s) in the Interrupt Mask register is(are) set. Enabling an interrupt by setting a mask bit (0→ ...
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... Audio Scrambler and Sub-Audio Signalling Processor 9 Configuration Guide 9.1 C-BUS Register Details © 2008 CML Microsystems Plc Page 37 CMX138 D/138_FI1.0/5 ...
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... Reset Operations A reset is automatically performed when power is applied to the CMX138. A reset can be issued BUS command, either as a General Reset command ($01 setting the appropriate bit (b5) in the Powerdown Control register ($C0). In the latter case, an option exists to protect the values held in the Program Block (which is accessed via the Programming register, $C8) ...
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... Page 39 CMX138 ...
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... AuxADC 0 off 0 = off 1 = enable 0 = off 1 = enable AUX DAC data / RAMDAC control 0 = disable 1 = enable 0 = AuxDAC operates normally 1 = AuxDAC operates as a RAMDAC RAMDAC functions. Page mode AuxADC ip select Data in b0-6 controls the D/138_FI1.0/5 CMX138 ...
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... DD Page 41 time(ms) 1024 10.50 512 5.25 256 2.63 128 1.31 64 0.66 32 0.33 16 0. AUX ADC data , $3FF = DV SS D/138_FI1.0/5 CMX138 1 0 ...
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... B15 B12 powersave 0 = powersave / bypass 1 = enabled b10 b9 Output Slew Rate 0 0 normal 0 1 slow 1 0 fast 1 1 fast Page Ref Clock divide ratio <8-0> B11 enabled D/138_FI1.0/5 CMX138 ...
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... CML Microsystems Plc DISC input gain DISC Input Gain b2 MIC Input Gain 0 0dB 1 3.2dB 0 6.4dB 1 9.6dB 0 12.8dB 1 16.0dB 0 19.2dB 1 22.4dB Idle 0 1 Idle Page 43 CMX138 DISC MIC input gain select D/138_FI1.0/5 0 ...
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... Page MIC-MOD bypass mute 0dB mute -22.4dB -19.2dB -16.0dB -12.8dB -9.6dB -6.4dB -3.2dB 0dB 3.2dB 6.4dB 9.6B 12.8dB 16.0dB 19.2dB 22.4dB CMX138 D/138_FI1.0/5 ...
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... Page Aux ADC threshold data BIAS Reset Prot XTAL DISC DIS bypass CMX138 MIC 0 bypass D/138_FI1.0/5 ...
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... Phase sub audio tone number: CTCSS / DCS / none 0 = off 1 = enabled 0 = off 1 = enabled 0 = off 1 = enabled 0 = off 1 = enabled 0 = off 1 = enabled 0 = off 1 = enabled 00 0 degrees (normal) 01 120 degrees 10 180 degrees 11 reserved Page Idle / mode D/138_FI1.0/5 CMX138 ...
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... User Defined CTCSS tone 253 select XTCSS maintenance tone 254 select DCS turn-off tone 255 Invalid tone Aux DCS 0 ADC 0 0 Page 47 CMX138 D/138_FI1.0 PRG ...
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... Tone Detected This word holds the current status of the CMX138 sub-audio and In-band tone sections. This word should be read by the host after an interrupt caused by a DCS, CTCSS or In-band tone event mode this register will be cleared to '0'. b15-11 Detected In-band frequency; identifies the frequency by its position in Table 5 In-band Tone. A change in the state of bits will cause bit 13 of the Status register ($C6), ‘ ...
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... C-BUS write to this register. This allows complex sequences (e.g. ring or alert tunes generated for the local speaker (Rx via the AUDIO pin) or transmitted signal (Tx via the MOD pin). © 2008 CML Microsystems Plc Frequency = Audio Tone (i.e. 1Hz per LSB) Page Audio Tone CMX138 1 0 D/138_FI1.0/5 ...
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... This C-BUS address is allocated for production testing and must not be accessed in normal operation. 3 AuxADC IRQ’s should be ignored / masked during mode changes: idle <-> Rx <-> Tx <-> idle. © 2008 CML Microsystems Plc Aux dcs 0 ADC 0 0 Page 50 CMX138 D/138_FI1.0/5 0 PRG ...
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... Programming Register Operation In order to support radio systems that may not comply with the default settings of the CMX138, a set of program register blocks is available to customise the features of the device envisaged that these blocks will only be written to following a power-on of the device and hence can only be accessed while the device is in IDLE mode ...
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... In-band tone detect bandwidth In-band tone detect bandwidth = 3.3V DD BANDWIDTH Will Decode Will Not Decode ±1.1% ±2.4% ±1.3% ±2.7% ±1.6% ±2.9% ±1.8% ±3. (see below) D/138_FI1.0/5 CMX138 Emph 1 0 Emph ...
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... User Defined CTCSS Code R 0 Reserved $000 $000 $000 $000 =3.3V, giving a range 0 to 824.8mV pk-pk CTCSS detect bandwidth = 3.3V DD BANDWIDTH Bit 0 Will Decode Will Not Decode 0 ±0.5% 1 ±0.8% 0 ±1.1% 1 ±1.3% 0 ±1.6% 1 ±1.8% CMX138 ±1.8% ±2.1% ±2.4% ±2.7% ±2.9% ±3.2% D/138_FI1.0/5 ...
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... User Defined CTCSS code Sub-audio Drop Out Time Reserved – set to $000 Page User Defined CTCSS Code [range 0 to 120ms D/138_FI1.0/5 CMX138 ...
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... D/138_FI1.0/5 CMX138 078 089 30 31 1D9 1F3 46 47 352 365 62 63 3FE 3FF ...
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... Fine Input Gain (unsigned integer Reserved - clear to ' Fine Output Gain 1 – AUDIO (unsigned integer) Fine Output Gain 2 – MOD (unsigned integer) Page D/138_FI1.0/5 CMX138 ...
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... DD /2) i.e. output limited from BIAS Reserved – set to $119A Pre-emp Page Ramp Rate Down control (RRD Comp Scramble D/138_FI1.0/5 CMX138 300Hz ...
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... Pre-emph Scrambler (optional) (optional) Figure 16 Default Tx Audio Filter line-up De-scrambler 300Hz Filter (optional) Figure 17 Default Rx Audio Filter line-up Page 58 Voice LPF & 300Hz Filter + Soft Limiter CTCSS De-emph Expander Audio (optional) (optional) D/138_FI1.0/5 CMX138 ...
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... Output mode w16 a7 3000 //voice mode - 12.5kHz filter, pre-emph, hpf, ctcss=151Hz w16 c2 34e0 //mode ctrl – In-band tone (1750Hz) on, CTCSS on, Tx w16 c1 0242 //tone control - select In-band tone w16 c3 8000 © 2008 CML Microsystems Plc Page 59 CMX138 D/138_FI1.0/5 ...
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... Audio Scrambler and Sub-Audio Signalling Processor delay 800 //mode ctrl - In-band tone off, ctcss on voice on, Tx w16 c1 4042 delay 800 //mode ctrl - ctcss off, voice on, Tx w16 c1 4002 © 2008 CML Microsystems Plc Page 60 CMX138 D/138_FI1.0/5 ...
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... DV + 0.3 DD −0 0.3 DD −30 ) +30 −20 + Min. Max. – 1100 – 11.1 −55 +125 −40 +85 Min. Max. 3.0 3.6 3.0 3.6 2.25 2.75 −40 +85 3.0 12.288 3.0 24.576 by the on-chip voltage DD CMX138 Unit Unit mW mW/°C °C °C Unit °C MHz MHz D/138_FI1.0/5 ...
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... D/138_FI1.0/5 CMX138 Unit µA µA mA µ µA µA µA µA µA ...
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... V BIAS BIAS D/138_FI1.0/5 CMX138 Unit µA µ µ µA µA µ kΩ must ...
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... D/138_FI1.0/5 CMX138 Unit ns ns kΩ pF kΩ MΩ kΩ dB MHz dB dB ...
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... AV –0 – – −1.0 0 +1.0 −1.0 0 +1.0 – 6 – – 200 – – – ±125 0.5 – AV –0 – – D/138_FI1.0/5 CMX138 Unit µ Ω kΩ µA V kΩ Ω kΩ µA V kΩ /2. DD ...
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... DD Page 66 CMX138 Typ. Max. Unit – 24 kΩ 10 – Bits – 80 62.4 – µs 100 – kΩ 5 – pF – ±20 mV – ±4 LSBs – ...
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... Max. – −26 – – 140 250 – 210 – – 160 – 60 – 260 – −26 – – 29 – – – 50 – – 20 288 – 3000 58 – – – 2 – CMX138 Unit mVp-p edges D/138_FI1.0/5 ...
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... Notes Min. Typ. – 4.0 – – 100 – 2:1 60.0 – – – −1 – 2.0 288 – – – 83 −1 – 2.0 – 134.4 81 −1.0 0 Page 68 CMX138 Max. Unit – ms – ms – mVrms – 260 Hz ±0.3 % +1.0 dB 4.0 % 3000 Hz ±0.3 % +1.0 dB 4.0 % – bps +1.0 dB D/138_FI1.0/5 ...
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... Typ. 91 300 – 92 300 – 93 300 – – 0 −2.0 0 33.0 – 96 – −50 94 – – −6 98 2632 3300 99 300 – 97 – – Page 69 CMX138 Max. Unit 3300 Hz 2550 Hz 3000 Hz – dB +0.5 dB – dB – dB – dB/oct – dB/oct 3496 Hz 3000 Hz 0.55 Vrms D/138_FI1.0/5 ...
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... 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 CMX138 can be used in conjunction with devices that comply with the slower timings, subject to system throughput constraints. ...
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... 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. © 2008 CML Microsystems Plc Order as part no. CMX138E1 Page 71 CMX138 D/138_FI1.0/5 ...