SigmaTel, Inc.
Data Sheet
STAC9721
4.4.4 Analog Mixer Input Gain Registers (Index 0Ch - 18h)
These registers control the gain/attenuation for each of the analog inputs. Each step
corresponds to approximately 1.5 dB. The MSB of the register is the mute bit. When
this bit is set to 1 the level for that channel is set at -∞ dB. Register 0Eh (Mic Volume
Register) has an extra bit that is for a 20dB boost. When bit D6 is set to 1, the +20 dB
boost is on. The default value is 8008, which corresponds to 0 dB gain, bost off, and
mute on. The default value for the mono registers is 8008h, which is to 0dB gain with
mute on. The default value for stereo registers is 8808h, which is 0 dB gain with mute
on.
. Analog Mixer Input Gain Register
Table 10
Mute
Gx4…Gx0
Function
0
0
0
1
00000
01000
11111
xxxxx
+12 dB gain
0 dB gain
-34.5 dB gain
-∞ dB gain
4.4.5 Record Select Control Register (Index 1Ah)
Used to select the record source independently for right and left. The default value is
0000h, which corresponds to MIC in.
. Record Select Control Registers
Table 11
SR2…SR0
Right Record Source
0
1
2
3
4
5
6
7
MIC
CD In (right)
Video In (right)
Aux In (right)
Line In (right)
Stereo Mix (right)
Mono Mix
Phone
. Left Record Select Control Registers
Table 12
SL2…SL0
Left Record Source
0
1
2
3
4
5
6
7
MIC
CD In (L)
Video In (L)
Aux In (L)
Line In (L)
Stereo Mix (L)
Mono Mix
Phone
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04/07/00
04/07/00
ETC [ ETC ]
