STAC9704 Datasheet, PDF (29/49 Pages) Hynix Semiconductor – Multimedia Audio Codec for AC97

SigmaTel, Inc.
STAC9704/7
4.4.6 Record Gain Registers (Index 1Ch)
The 1Ch register adjusts stereo input record gain. Each step corresponds to 1.5 dB. 22.5 dB
corresponds to 0F0Fh and 000Fh respectively. The MSB of the register is the mute bit. When this bit
is set to 1, the level for that channel(s) is set at -∞ dB.
The default value is 8000h, which corresponds to 0 dB gain with mute on.
Table 14: Record Gain Registers
MUTE
0
0
1
GX3… GX0
1111
0000
xxxx
FUNCTION
+22.5 dB gain
0 dB gain
-∞ gain
4.4.7 General Purpose Register (Index 20h)
This register is used to control some miscellaneous functions. Below is a summary of each bit and its
function. The MS bit controls the mic selector. The LPBK bit enables loopback of the ADC output to
the DAC input, without involving the AC-link, allowing for full system performance measurements.
Table 15: General Purpose Register
BIT
3D
MIX
MS
LPBK
FUNCTION
3D Stereo Enhancement on/off 1 = on
Mono output select 0 = Mix, 1= Mic
Mic select 0 = Mic1, 1 = Mic2
ADC/DAC loopback mode
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10/02/98