STAC9752A Datasheet, PDF (29/106 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
Figure 13. STAC9752A/9753A Powerdown Timing
SYNC
BIT_CLK
SDATA_OUT
SDATA_IN
Note: BIT_CLK not to scale
slot 2
per
frame
TAG
Write to
0x20
DATA
PR4
slot 2
per
frame
TAG
4.6.2.
BIT_CLK and SDATA_IN are transitioned low immediately following decode of the write to the Pow-
erdown Register (26h) with PR4. When the AC‘97 Controller driver is at the point where it is ready to
program the AC-Link into its low power mode, slots 1 and 2 are assumed to be the only valid stream
in the audio output frame.
After programming the AC‘97 device to this low power, halted mode, the AC‘97 Controller is required
to drive and keep SYNC and SDATA_OUT low.
Once the AC‘97 CODEC has been instructed to halt BIT_CLK, a special “wake-up” protocol must be
used to bring the AC-Link to the active mode since normal audio output and input frames can not be
communicated in the absence of BIT_CLK.
Waking up the AC-Link
There are two methods for bringing the AC-Link out of a low power, halted mode. Regardless of the
method, it is the AC‘97 Controller that performs the wake-up task.
4.6.2.1. Controller Initiates Wake-up
AC-Link protocol provides for a “Cold AC‘97 Reset”, and a “Warm AC‘97 Reset”. The current power-
down state would ultimately dictate which form of AC‘97 reset is appropriate. Unless a “cold” or “reg-
ister” reset (a write to the Reset Register) is performed, wherein the AC‘97 registers are initialized to
their default values, registers are required to keep state during all powerdown modes.
Once powered down, re-activation of the AC-Link via re-assertion of the SYNC signal must not occur
for a minimum of four audio frame times following the frame in which the powerdown was triggered.
When AC-Link powers up the CODEC indicates readiness via the CODEC Ready bit (input slot 0, bit
15).
4.6.2.2. CODEC Initiates Wake-up
The STAC9752A/9753A (running off Vaux) can trigger a wake event (PME#) by transitioning
SDATA_IN from low to high and holding it high until either a warm or cold reset is observed on the
IDT™
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AC’97 2.3 CODECS WITH STEREO MICROPHONE & UNIVERSAL JACK
STAC9752A/9753A
V 1.5 1206