CMX983 Datasheet, PDF (27/93 Pages) CML Microcircuits – Programmable Channel Filter

Analogue Front End (AFE) for Digital Radio
CMX983
The following C-BUS registers control the signal routing, gain setting and overflow status of the two Rx input
circuits:
RX_INPUT - $1D: 16-bit Write
Reset value = $0000
Bit:
15 14 13 12 11 10 9
8
Cal
select
Rx B
enable
ADC
B
invert
Rx B gain
(-12dB … 12dB, +mute)
7
6
5
0
Rx A
enable
ADC
A
invert
4
3
2
1
0
Rx A gain
(-12dB … 12dB, +mute)
RX_INPUT b15: Calibration select
When this bit is set to 1 the calibration pin CALI is connected to channel A positive input, CALQ is
connected to channel B positive input, and the mid-rail reference voltage V_BIAS is buffered and applied
to both the channel A and B negative inputs. Also, the Rx A and Rx B programmable gain amplifiers
are automatically set to 0 dB while the calibration select bit is set to 1.
RX_INPUT b14: Rx B enable
Set to 1 to enable channel B gain stage and ADC modulator.
RX_INPUT b13: ADC B invert
Set to 1 to invert the channel B modulator output.
RX_INPUT b12-8: Rx B gain
Set channel B input gain to between -12dB and +12dB in 1dB steps, or mute the output. The gain
setting is in 2’s complement format:
10000 = mute
10100 = -12.0dB
10101 = -11.0dB
...
11111 = -1.0dB
00000 = 0.0dB
00001 = 1.0dB
...
01011 = 11.0dB
01100 = 12.0dB
RX_INPUT b7: Reserved, set to 0
RX_INPUT b6: Rx A enable
Set to 1 to enable channel A gain stage and ADC modulator.
RX_INPUT b5: ADC A invert
Set to 1 to invert the channel A modulator output.
RX_INPUT 4-0: Rx A gain
Set channel A input gain, similar in operation to bits 12-8.
 2015 CML Microsystems Plc
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