SigmaTel, Inc.
Data Sheet
STAC9721
4.4.7 3D Control Register (Index 22h)
This register is used to control the 3D stereo enhancement function, SigmaTel Surround
3D (SS3D), built into the codec. SS3D provides for a wider soundstage and speaker
separation for 2-speaker arrangements. Register bits, DP3-DP2 are used to control the
separation ratios in the 3D control for LINE_OUT. The 3D bit in the general purpose
register (register 20h bit D13) must be set to 1 to enable SS3D functionality and for the
bits in 22h to take effect.
Table 15. 3D Control Registers
DP3..DP0
LINE_OUT
Separation Ratio
00XX
01XX
10XX
11XX
0 (Off)
3 (Low)
4.5 (Med.)
6.0 (High)
The three separation ratios are implemented as shown above. The separation ratio defines
a series of equations that determine the amount of depth difference (High, Medium, and
Low) perceived during two-channel playback. The ratios provide an indication of how
much soundstage increase can be expected.
4.4.8 Powerdown Control/Status Register (Index 26h)
This read/write register is used to program powerdown states and monitor subsystem
readiness. The lower half of this register is read only status, a “1” indicating that the
subsection is “ready”. Ready is defined as the subsection’s ability to perform in its
nominal state. When this register is written, bits D7:D0 will not be affected. Bit D15
controls the External Amplifier Power Down pin.
When the AC-Link “Codec Ready” indicator bit (SDATA_IN slot 0, bit 15) is a 1, it
indicates that the AC-Link and AC'97 control and status registers are in a fully
operational state.
The AC'97 controller must further probe this Powerdown
Control/Status Register (D3:D0) to determine exactly which subsections, if any are ready.
Table 16. Powerdown Status Registers
BIT
FUNCTION
EAPD
REF
External Amplifier Power Down
Indicates VREF is at nominal level
Analog mixers, etc. ready
ANL
DAC
ADC
DAC section ready to playback data
ADC section ready to playback data
25
04/07/00
04/07/00
ETC [ ETC ]
