FRS Signalling Processor
CMX882
1.6.8
$C1 MODE CONTROL: 16-bit write-only
15
14
13
12
11
10
9
8
0
Bit:
Enable
Voice
In band signalling:
Generate
Enable
Enable DCS
Inverse
Enable DCS
In-band tone, XTCSS
Audio Tone
CTCSS
7
0
6
0
5
0
4
3
2
0
1
0
Bit:
Enable
Enable
Mode Select
2400b/s
1200b/s
Bits 1 and 0 control the overall mode of the CMX882 according to the table below:
Bit 1
Bit 0
Device Mode
0
0
1
1
0
1
0
1
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 µC 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 Bit 3
Tx - Transmitted signal
Rx - Monitored signal(s)
0
0
1
1
0
1
0
1
None
None
MSK 1k2b/s
MSK 2k4b/s
Reserved
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
Bit 10
Bit 9
Tx - Transmitted signal:
Rx - Monitored signal(s):
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
No Sub-Audio Transmitted
Inverted DCS*
DCS
No Sub-audio Monitoring
Inverted DCS*
DCS
Do not use
DCS + inv DCS*
CTCSS
CTCSS
Do not use
CTCSS + inv DCS*
CTCSS + DCS
CTCSS + DCS + inv DCS*
Do not use
Do not use
* 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
CMLMICRO [ CML MICROCIRCUITS ]
