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SigmaTel, Inc.
Data Sheet
STAC9721
19
04/07/00
04/07/00
Warm Reset - a warm reset will re-activate the AC-Link without altering the current
STAC9721/23 register values. A warm reset is signaled by driving SYNC high for a
minimum of 1us in the absence of BIT_CLK.
Note: Within normal audio frames, SYNC is a synchronous input. However, in the
absence of BIT_CLK, SYNC is treated as an asynchronous input used in the generation
of a warm reset to the STAC9721/23.
4. STAC9721/23 MIXER
The STAC9721/23 mixer is designed to the AC'97 specification to manage the playback and record of all
digital and analog audio sources in the PC environment. These include:
• System Audio: digital PCM input and output for business, games and multimedia
• CD/DVD: analog CD/DVD-ROM Redbook audio with internal connections to Codec mixer
• Mono microphone: choice of desktop mic, with programmable boost and gain
• Speakerphone: use of system mic and speakers for telephone, DSVD, and video conferencing
• Video: TV tuner or video capture card with internal connections to Codec mixer
• AUX/synth: analog FM or wavetable synthesizer, or other internal source
Figure 10. STAC9721/23 Mixer Functional Diagram
vol
mute
PCM out
D/A
Phone
LINE IN
LINE_OUT
CD
Video
AUX
Analog Audio
Sources
MONO_OUT
PCM IN
20dB
Master
Volume
Mono
Volume
A/D
A/D
Master
Input
Volume
Σ
Σ
vol
vol
vol
vol
vol
vol
vol
mute
mute
mute
mute
mute
mute
mute
KEY
MonoAnalog
StereoAnalog
Digital
LNLVL_OUT
LNLVL
Volume
3D
3D
-6dB
-6dB
PC_Beep
MIC1
MIC2
Σ
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