STAC9752A Datasheet, PDF (34/106 Pages) Integrated Device Technology – AC’97 2.3 CODECS WITH STEREO MICROPHONE & UNIVERSAL JACK

STAC9752A/9753A
AC’97 2.3 CODECS WITH STEREO MICROPHONE & UNIVERSAL JACK
PC AUDIO
5.2.3.
AC-Link input frame signal which active output slots require data from the AC‘97 Digital Controller in
the next audio output frame. An active output slot is defined as any slot supported by the CODEC
that is not in a power-down state. For fixed 48KHz operation the SLOTREQ bits are always set
active (low) and a sample is transferred in each frame.
For variable sample rate input, the tag bit for each input slot indicates whether valid data is present
or not. Thus, even in variable sample rate mode, the CODEC is always the master: for SDATA_IN
(CODEC to Controller), the CODEC sets the TAG bit; for SDATA_OUT (Controller to CODEC), the
CODEC sets the SLOTREQ bit and then checks for the TAG bit in the next frame.
The VRM (Variable Rate Mic Audio) bit in the Extended Audio Status and Control Register controls
the optional MIC ADC input behavior in the same way that VRA = 1 controls the PCM ADC.
5.2.2.1. SLOTREQ Behavior and Power Management
SLOTREQ bits for fixed rate, powered down, and all unsupported Slots should be driven with 0s for
maximum compatibility with the original AC '97 Component Specification. When a DAC channel is
powered down, it disappears completely from the serial frame: output tag and slot are ignored, and
the SLOTREQ bit is absent (forced to zero).
When the Controller wants to power-down a channel, all it needs to do is:
1. Disable source of DAC samples in Controller
2. Set PR bit for DAC channel in Registers 26h, 2Ah, or 3Eh
When it wants to power up the channel, all it needs to do is:
1. Clear PR bit for DAC channel in Registers 26h, 2Ah, or 3Eh
2. Enable source of DAC samples in Controller
Primary and Secondary CODEC Register Addressing
The 2-bit CODEC ID field in the LSBs of Output Slot 0 is an addition to the original AC-Link protocol
that enables an AC‘97 Digital Controller to independently access Primary and Secondary CODEC
registers.
For Primary CODEC access, the AC‘97 Digital Controller:
1. Sets the AC-Link Frame valid bit (Slot 0, bit 15).
2. Validates the tag bits for Slot 1 and 2 Command Address and Data (Slot 0, bits 14 and 13).
3. Sets a zero value (00) into the CODEC ID field (Slot 0, bits 1 and 0).
4. Transmits the desired Primary CODEC Command Address and Command Data in Slots 1 and
2.
For Secondary CODEC access, the AC‘97 Digital Controller:
1. Sets the AC-Link Frame valid bit (Slot 0, bit 15).
IDT™
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AC’97 2.3 CODECS WITH STEREO MICROPHONE & UNIVERSAL JACK
STAC9752A/9753A
V 1.5 1206