STAC9704 Datasheet, PDF (26/49 Pages) Hynix Semiconductor – Multimedia Audio Codec for AC97

SigmaTel, Inc.
STAC9704/7
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
0
0
1
Mx5…Mx0
00 0000
01 1111
xx xxxx
FUNCTION
0dB Attenuation
46.5 Attenuation
∞ dB Attenuation
RANGE
Req.
Req.
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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10/02/98