PMR Signalling Processor
CMX881
0
1.6.9
$C2 AUDIO & CTCSS CONTROL: 16-bit write-only
Bit:
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
Special
Sub-Audio
0
0
0
Voice filter mode
0
0
CTCSS tone
Bits 5 to 0 select the CTCSS tone to be used in both Tx and Rx modes, the range of valid addresses is 0-
39 (in decimal). In Tx this number will be used to select the CTCSS tone, if the tone number is outside
the valid range no signalling will occur. In Rx this address will be searched for when CTCSS is enabled
in the Mode register and if detected, this number will be indicated in the Tone Status register $CC.
Bits 9 and 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. 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
-
DCS turn off tone
Reserved - do not set
Clone
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
Bits 15 to 13 and 7 to 6 are reserved – set to ‘0’.
1.6.10
$C3 Tx In-Band Tones: 16-bit write-only
Bit:
15
14
13
12
11
10
9
8
7
0
6
0
5
4
3
2
1
0
Tx Selcall tone
0
0
0
Twist
Single
Tx DTMF tone
Bits 15 to 11 define the tone transmitted when Tx Selcall is enabled. The frequency is as defined in
Table 5 Selcall Tones.
Bits 10 to 6 are reserved – set to ‘0’.
Bit 5 controls DTMF twist, when set to '0' the two tones are sent at the same level, when set to '1' the
amplitude of the lower frequency tone is 2dB below the amplitude of the higher tone.
Bit 4 controls whether a single tone is generated when transmitting DTMF, when set to '0' dual tones are
sent, when set to '1' the single tone identified in Table 8 is sent on it's own.
Bits 3 to 0 define the signals produced when Tx DTMF is enabled. The frequencies are as defined in
Table 8 DTMF Tone Pairs and Corresponding Tx Programming Codes.
1.6.11
$C7 Reserved - Do not write to this register
2004 CML Microsystems Plc
36
D/881/7
CMLMICRO [ CML MICROCIRCUITS ]
