PMR Signalling Processor
CMX881
CONTENTS
Section
Page
1.0
1.1
1.2
1.3
1.4
Features........................................................................................................................1
Brief Description............................................................................................................1
Block Diagram...............................................................................................................7
Signal List .....................................................................................................................8
External Components..................................................................................................10
1.4.1 PCB Layout Guidelines and Power Supply Decoupling ...................................11
1.4.2 Modulator Outputs ..........................................................................................12
General Description.....................................................................................................13
1.5.1 Sleep Mode and Auto Start Up........................................................................14
1.5.2 Auxiliary ADC .................................................................................................14
1.5.3 Receive Mode.................................................................................................15
1.5.4 Transmit Mode................................................................................................22
1.5.5 FFSK/MSK Data packeting .............................................................................26
1.5.6 C-BUS Operation............................................................................................28
C-BUS Register Description ........................................................................................29
Application Notes ........................................................................................................47
1.7.1 CRC and Parity information ............................................................................47
Performance Specification...........................................................................................48
1.8.1 Electrical Performance....................................................................................48
1.8.2 Packaging.......................................................................................................58
1.5
1.6
1.7
1.8
Table
Page
Table 1 Concurrent Rx Signalling Modes Supported by the CMX881 ....................................... 15
Table 2 CTCSS Tones............................................................................................................. 18
Table 3 DCS Modulation Modes............................................................................................... 18
Table 4 DCS 23 Bit Codes ....................................................................................................... 19
Table 5 Selcall Tones .............................................................................................................. 20
Table 6 Concurrent Tx Modes Supported by the CMX881........................................................ 22
Table 7 Data Frequencies for each Baud Rate......................................................................... 25
Table 8 DTMF Tone Pairs and Corresponding Tx Programming Codes ................................... 26
Table 9 Maximum Data Transfer Latency................................................................................. 27
Figure
Page
Figure 1 Block Diagram .............................................................................................................7
Figure 2 Recommended External Components........................................................................ 10
Figure 3 Power Supply Connections and De-coupling .............................................................. 11
Figure 4 Modulator output components to achieve -100dB/decade roll-off................................ 12
Figure 5 Rx Audio Filter Frequency Response ......................................................................... 16
Figure 6 De-emphasis Curve for TIA/EIA-603 Compliance....................................................... 16
Figure 7 Low Pass Sub-Audio Band Filter for CTCSS and DCS ............................................... 17
Figure 8 25kHz Channel Audio Filter Response Template........................................................ 23
Figure 9 12.5kHz Channel Audio Filter Response Template..................................................... 23
Figure 10 Audio Frequency Pre-emphasis Template................................................................ 24
Figure 11 Modulating Waveforms for 1200 and 2400 Baud FFSK/MSK Signals....................... 25
Figure 12 C-BUS Transactions................................................................................................. 28
Figure 13 Possible PMR Configuration..................................................................................... 47
Figure 14 C-BUS Timing.......................................................................................................... 56
2004 CML Microsystems Plc
5
D/881/7
CMLMICRO [ CML MICROCIRCUITS ]
