Audio Codec '97

AC ‘97 Component Specification Revision 2.3 Rev 1.0
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4.5.4 The Codec-Ready Bit and Audio or Modem DAC/ADC Status Bits
AC ‘97 compliance requires that Codec-Ready and audio or modem DAC/ADC status bits only change from
“ready” to “not ready” in response to a PR state change issued by the Controller to the Powerdown Control/Status
Registers 26h, 2Ah, or 3Eh. This ensures that once data is actively flowing on a slot, the Controller or Driver does
not have to continuously read the registers to detect any unexpected Codec PR status change.
5. Audio Features
L RC
S S
4 channel Surround
(Home Theater)
via line level out
LNLVL_OUT
L C R
S
L
S
R
LFE
5.1 channel Digital
(DVD movie
& DVD audio)
CE home theater
via S/PDIF
SPDIF_OUT*
Analog sources (legacy)
•CD/DVD: Redbook audio
•VIDEO*: TV tuner or VidCap
•
A
U
X
*: internal source
AC ’97
Analog
Codec
AC-link
PHONE*
MONO_OUT*
MIC_IN
LINE_IN
Speakerphone I/O
(legacy)
L R
Stereo audio
(w/ 3D positional)
(all PC audio)
via line out
MIC_IN
LINE_OUT
+
L
R
S
L
S
R
Discrete 4 channel
(3D PC Games)
via
line out + 4CH out
LINE_OUT
4CH_OUT*
+
LINE_OUT
AUX_OUT
or 4CH_OUT*
or HP_OUT*
SPDIF_OUT*
LNLVL_OUT
analog mono
analog stereo
optional
*
Key
Figure 15. Audio I/O
5.1 Overview
AC ‘97’s PCM Digital to Analog Converters (DACs) support stereo (optional multichannel) output that contains a
mix generated in the AC '97 Controller of all digital audio sources. PCM output is mixed with analog mixer
sources, processed with optional 3D stereo enhancement, loudness and tone controls, and sent to LINE_OUT and
the independently controlled AUX_OUT, which by default functions as a line level output. AUX_OUT can
optionally be configured as headphone or 4-channel output.
MONO_OUT was originally designed for analog speakerphone connections, and can be configured as either
microphone only or a mix of sources.
The PCM Analog to Digital Converters (ADCs) support an input capability that can record any mono or stereo
source, or a mix of sources. The optional third PCM ADC is dedicated to voice input, and also extends the range of
acoustic echo cancellation (AEC) capabilities.
Consumer equipment (CE) compatible digital output is supported via optional SPDIF_OUT. Linear PCM or
encoded digital formats, such as Dolby Digital** streams are supported via S/PDIF.
The AC ‘97 architecture supports a variety of audio output options, including:
• Analog stereo output (LINE_OUT) transmitted to amplified stereo PC speaker array via stereo mini-jack.