Cocr Mute Bit (Mut) Bit 10; Cocr Microphone Gain Select Bits (Mgs1-0) Bits 11,12 - Motorola DSP56156 Manual

INTERFACE WITH THE DSP56156 CORE PROCESSOR
Table 6-3 Audio Level Control with DSP Filter Gain
VC3 VC2 VC1 VC0
0 0
0 0
0 0
0 0
0 1
0 1
0 1
0 1
1 0
1 0
1 0
1 0
1 1
1 1
1 1
1 1
6.4.5.2 COCR Codec Ratio Select Bits (CRS1-0) Bits 8,9
The Codec Ratio Select Bits are used by the DSP core to program the decimation and
interpolation ratio of the on-chip codec comb filter sections. As shown in Table 6-4, the
value selected as decimation and interpolation ratio also affects the DC gain of the comb
filter in the A/D and D/A sections. The overall DC gain of the A/D and D/A sections is dis-
cussed in detail Sections 6.5.1 and 6.5.2.
Table 6-4 Decimation/Interpolation Ratio Control
CRS1 CRS0 Decimation
Interpolation
0 0
0 1
1 0
1 1
6.4.5.3

COCR Mute Bit (MUT) Bit 10

The mute bit is used to mute the output signal. When the MUT bit is cleared, the output
signal is muted. When the MUT bit is set, the output signal is not muted.
6.4.5.4

COCR Microphone Gain Select Bits (MGS1-0) Bits 11,12

The Microphone Gain Select Bits are used by the DSP core to program the analog input
gain. The values are given in Table 6-5. The analog modulator is guaranteed to be linear
6 - 8
Relative Level Digital Filter Final Output
dB
0 0 -20
0 1 -15
1 0 -10
1 1 -5
0 0 0
0 1 6
1 0 12
1 1 18
0 0 0
0 1 6
1 0 12
1 1 18
0 0 24
0 1 30
1 0 30
1 1 35
A/D Comb Filter
DC Gain
Ratio Rate
3 21
125 125 /2
128 1
3 21
105 2(105 )/2
3 21
81 2(81 )/2
DSP56156 ON-CHIP SIGMA/DELTA CODEC
Gain Level
0 -20
0 -15
0 -10
0
0
-1
-2
-3
0
-1
-2
-3
-4
-5
0
0
D/A Comb Filter
DC Gain
-0.618 dB 125/128
0 dB 1
0.859 dB 105/128
0.118 dB 81/128
-5
0
5
10
15
0
5
10
15
20
25
30
35
-0.206 dB
0 dB
-1.720 dB
-3.974 dB
MOTOROLA