STAC9750 Datasheet, PDF (40/73 Pages) Integrated Device Technology – VALUE-LINE TWO-CHANNEL AC’97 CODECS

STAC9750/9751
VALUE-LINE TWO-CHANNEL AC’97 CODECS
PC AUDIO
6.5.8.
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.
Bit
3D
MIX
MS
POP BYP
LPBK
Table 21. General Purpose Register
Function
3D Stereo Enhancement ON/OFF - 1 = on
Mono output select - 0 = Mix, 1= Mic
Mic select - 0 = Mic1, 1 = Mic2
DAC bypasses mixer and connects directly to Line Out
ADC/DAC loopback mode
3D Control (22h)
Default: 0000h
D15
D14
D13
D7
D6
D5
Reserved
D12
D11
D10
Reserved
D4
D3
D2
DP3
DP2
D9
D8
D1
D0
Reserved
This register is used to control the 3D stereo enhancement function, IDT Surround 3D (SS3D), built
into the AC'97 component. Note that register bits DP3-DP2 are used to control the separation ratios
in the 3D control for LINE_OUT. SS3D provides for a wider soundstage extending beyond the nor-
mal 2-speaker arrangement. Note that the 3D bit in the general purpose register (20h) must be set to
1 to enable SS3D functionality and for the bits in 22h to take effect.
DP3, DP2
00
01
10
11
Table 22. 3D Control Registers
LINE_OUT SEPARATION RATIO
0 (Off)
3 (Low)
4.5 (Med)
6 (High)
The three separation ratios are implemented as shown in Table 22. The separation ratio defines a
series of equations that determine the amount of depth difference (High, Medium, and Low) per-
ceived during two-channel playback. The ratios provide for options to narrow or widen the sound-
stage.
IDT™
VALUE-LINE TWO-CHANNEL AC’97 CODECS
40
STAC9750/9751
V 5.8 103106