Audio Scrambler and Sub-Audio Signalling Processor
CMX138A
MIC - MOD bypass
gain
MIC Input
MOD Output
Enable: $C0:1
Gain: $B1:5-2
MOD output
gain
Enable: $C0:8
Enable: $C0:14
Gain: $B0:4-2
Enable: $C0:11
Gain: $B1:12-10
DISC Input
DISC – AUDIO
bypass gain
Enable: $C0:2
Gain: $B1:9-6
Select: $B0:5
AUDIO
Output
AUDIO
output gain
Enable: $C0:12
Gain: $B1:15-13
Enable: $C0:10
Enable: $C0:15
Gain: $B0:10-8
Input Select
Tx MOD
Enable: $C0:13
mux
Enable: $A7:13-12
mux
Select: $B0:1-0
Enable: $C0:6
Signal Processing
Figure 5 Signal Routing
The analogue gain/attenuation of each input and output can be set individually, with additional Fine Gain
control available via the Programming registers.
See:
o
o
o
Analogue Input Gain - $B0 write
Analogue Output Gain - $B1 write
Audio Tone - $CD: 16-bit write.
7.3.2 Mode Control
The CMX138A operates in one of three modes:
o
o
o
Idle
Rx
Tx
At power-on or following a Reset, the device will automatically enter Idle mode, which allows for the
maximum powersaving whilst still retaining the capability of monitoring the AuxADC input (if enabled). It is
only possible to write to the Programming register whilst in Idle mode.
See:
o
Mode Control – $C1 write.
© 2010 CML Microsystems Plc
Page 16
D/138A/2
CMLMICRO [ CML MICROCIRCUITS ]
