STAC9704 datasheet(30/49 Pages) HYNIX

30 / 49 page

SigmaTel, Inc.

STAC9704/7

10/02/98

4.4.8

3D Control Register (Index 22h)

This register is used to control the 3D stereo enhancement function, Sigmatel Surround 3D (SS3D),

built into the AC'97 component. Note the register bits, DP1 – DP0, are used to control the separation

ratios in the 3D control. SS3D provides for a wider soundstage extending beyond the normal 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.

Table 16: 3D Control Registers

DP1 – DP0

SEPARATION

RATIO

0 0

3 (Default)

0 1

3 (Low)

1 0

4.5 (Med.)

1 1

6 (High)

3 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 for options to narrow or widen the soundstage.

4.4.9

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, the bit

values that come in on AC-link will have no effect on read only bits 0-7.

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 to determine exactly which subsections, if

any are ready.

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