Baseband Processor For Mixed Mode Land Mobile Radio
CMX880
$B1 ANALOGUE OUTPUT PATH CONFIGURATION: 16-bit write-only
Bit:
15
14
13
12
11
10
0
9
0
8
0
7
0
6
0
5
4
3
2
1
0
Data
DAC1
Dest
MOD2
Source
SA
Dest
MOD 1
Attenuation
MOD 2
Attenuation
Source
Data source (to DAC 1)
Bit 15
Bit 14
0
0
1
1
0
1
0
1
No output data source selected
C-BUS
FSB
Internal (from SD ADC)
DAC 1 destination
MOD 2 source
Bit 13
Bit 12
0
1
Audio output port
Modulator output ports (MOD_1 and,
if Bit 12 = 0, MOD_2)
0
1
DAC 1
DAC 2
Sub-Audio destination
Bit 11
0
1
Composite Sub-audio + in-band signal to both DACs
In-band signal to DAC 1; Sub-audio to DAC 2
Fine output gain control 2 is only available when bit 12 is set to 1. To utilise the independent fine output
attenuation controls, when transmitting using two point modulation, bit 12 should be set to 1. If the coarse
adjustment is sufficiently accurate, then clearing bit 12 to 0 can save power.
When transmitting ‘CQPSK’ bit 12 must be set to 1. During ‘CQPSK’ transmission the ‘I’ component is routed to
the MOD_1 output via DAC 1 and the ‘Q’ component is routed to the MOD_2 output via DAC 2. The state of bit
11 does not affect operation of CQPSK transmission.
When transmitting ‘voice + sub-audio’ with voice and sub-audio routed to separate modulator output ports, bit 12
must be set to 1. During ‘voice + sub-audio’ transmission the voice can be routed to the MOD_1 output via DAC
1 and the sub-audio signal routed to the MOD_2 output via DAC 2, or the voice and sub-audio can be combined
and either routed to both MOD_1 and MOD_2 via DAC 1 or MOD_1 via DAC 1 and MOD_2 via DAC 2. The
facility to merge sub-audio with voice or to keep them separate is controlled by ‘SA Dest’ bit (bit 11).
NOTE: voice in this context refers to any of the ‘ín-band’ signals; voice, Selcall tone, DTMF tones or FFSK/MSK.
Bits 6 to 10 reserved - set to 0.
MOD 1 Output
Attenuation
MOD 2 Output
Attenuation
Bit 5 Bit 4 Bit 3
Bit 2 Bit 1 Bit 0
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
4dB
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
4dB
2dB
0dB
2dB
0dB
Note:
The output paths provide user programmable attenuation stages to independently adjust the modulators’ output
levels. Finer level control of the ‘MOD 1’ output can be achieved with the ‘FINE OUTPUT GAIN 1’ control
register and fine level control of the ‘MOD 2’ output can be achieved with the ‘FINE OUTPUT GAIN 2’ control
register.
ã 2001 Consumer Microcircuits Limited
44
D/880/1
CMLMICRO [ CML MICROCIRCUITS ]
