FRS Signalling Processor
CMX882
0
1.6.9
$C2 AUDIO & DEVICE ADDRESS CONTROL: 16-bit write-only
Bit:
15
0
14
13
12
11
10
9
8
7
6
5
4
3
2
1
Special
Sub-Audio
Scramble
Compand
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
select the XTCSS maintenance tone in this register when receiving. If the Tone CloneTM 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
Bit 8
Freq (Hz)
Special Sub-Audio tone
0
0
1
1
0
1
0
1
-
None
134.4
64.7
Clone
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 pre-
emphasis (Tx) mode of the voice band filtering.
Bit 12
Bit 11
Bit 10
Voice filter mode
X
X
0
0
1
1
X
X
0
1
0
1
0
Disable de/pre-emphasis
Enable de/pre-emphasis
No filtering applied
1
X
X
X
X
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
CMLMICRO [ CML MICROCIRCUITS ]
