STAC9704 datasheet(26/49 Pages) HYNIX

26 / 49 page

SigmaTel, Inc.

STAC9704/7

10/02/98

4.4.1 Reset Register (Index 00h)

Writing any value to this register performs a register reset, which causes all registers to revert to their

default values. Reading this register returns the ID code of the part.

4.4.2 Play Master Volume Registers (Index 02h, 04h, and 06h)

These registers manage the output signal volumes. Register 02h controls the stereo master volume

(both right and left channels), register 04h controls the optional stereo true line level out, and register

06h controls the mono volume output. Each step corresponds to 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. ML5 through ML0 is for

left channel level, MR5 through MR0 is for the right channel and MM5 through MM0 is for the mono

out channel.

The default value is 8000h (1000 0000 0000 0000), which corresponds to 0 dB attenuation with mute

on.

Table 10: Play Master Volume Register

MUTE

Mx5…Mx0

FUNCTION

RANGE

00 0000

0dB Attenuation

Req.

01 1111

46.5 Attenuation

Req.

xx xxxx

∞ dB Attenuation

Req.

4.4.3 PC Beep Register (Index 0Ah)

This register controls the level for the PC Beep input. Each step corresponds to approximately 3 dB of

attenuation. 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. PC_BEEP supports motherboard implementations. The intention of routing

PC_BEEP through the STAC9704/7 mixer is to eliminate the requirement for an onboard speaker by

guaranteeing a connection to speakers connected via the output jack. In order for this to be viable the

PC_BEEP signal needs to reach the output jack at all times. NOTE: the PC_BEEP is recommended to

be routed to L & R Line outputs even when the STAC9704/7 is in a RESET state. This is so that

Power On Self Test (POST) codes can be heard by the user in case of a hardware problem with the PC.

For further PC_BEEP implementation details please refer to the AC’97 Technical FAQ sheet. The

default value can be 0000h or 8000h, which corresponds to 0 dB attenuation with mute off or on.

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