PMR Signalling Processor
CMX881
1.6.3
$B0 ANALOGUE GAIN: 16-bit write-only
Bit:
15
14
13
12
11
10
9
8
7
0
6
5
4
3
2
1
0
MOD_1
MOD_2
Input
Gain
Audio Output
Attenuation
Inv_1
Inv_2
Attenuation
Attenuation
Bits 15 and 11 set the phase of the MOD_1 and MOD_2 outputs. When set to '0' the 'true' signal (0°
phase shift) will be produced, when set to '1' the signal will be inverted (180° phase shift). This can be
useful when interfacing with rf circuitry or when generating an inverted turn off tone for CTCSS. Any
change will take place immediately after these bits are changed.
The output paths provide user programmable attenuation stages to independently adjust the output levels
of the modulators. Finer level control of the MOD_1 and MOD_2 outputs can be achieved with the FINE
OUTPUT GAIN 1 and FINE OUTPUT GAIN 2 registers (P4.2-3).
MOD_1 Output
Attenuation
MOD_2 Output
Attenuation
Bit 14 Bit 13 Bit 12
Bit 10 Bit 9 Bit 8
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
>40dB
12dB
10dB
8dB
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
>40dB
12dB
10dB
8dB
6dB
6dB
4dB
4dB
2dB
2dB
0dB
0dB
Bit 7 is reserved - set to 0.
Bits 6 to 4 control the input path programmable gain stage - useful when amplifying low power voice
signals from the microphone inputs. Finer gain control can be achieved with the ‘FINE INPUT GAIN’
control register (P4.0). In receive mode it is recommended to set the gain to 0dB.
Audio Output
Bit 6 Bit 5 Bit 4
Input Gain
Bit 3 Bit 2 Bit 1 Bit 0
Attenuation
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0dB
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
>60dB
44.8dB
41.6dB
38.4dB
35.2dB
32.0dB
28.8dB
25.6dB
22.4dB
19.2dB
16.0dB
12.8dB
9.6dB
3.2dB
6.4dB
9.6dB
12.8dB
16.0dB
19.2dB
22.4dB
6.4dB
3.2dB
0dB
Bits 3 to 0 control the output path programmable attenuation stage to adjust the volume of the audio
output signal. Finer volume control can be achieved with the ‘FINE OUTPUT GAIN 1’ control register
(P4.2).
2004 CML Microsystems Plc
31
D/881/7
CMLMICRO [ CML MICROCIRCUITS ]
