Intel PXA26X - Manual (Page 472)

13-10 Intel® PXA26x Processor Family Developer’s Manual
AC97 Controller Unit
13.4.2.2 Slot 1: Status Address Port/SLOTREQ bits
The status port monitors the status for the ACUNIT functions including, but not limited to, mixer
settings and power management.
Audio input frame slot 1’s stream echoes the control register index for the data to be returned in
slot 2, if the controller tags slots 1 and 2 valid during slot 0.
The controller only accepts status data if the accompanying status address matches the last valid
command address issued during the most recent read command.
For multiple sample rate output, the codec examines its sample-rate control registers, its FIFOs’
states, and the incoming SDATA_OUT tag bits at the beginning of each audio output frame to
determine which SLOTREQ bits to set active (low). SLOTREQ bits asserted during the current
audio input frame indicate which output slots require data from the controller in the next audio
output frame. For fixed 48-KHz operation, the SLOTREQ bits are set active (low), and a sample is
transferred each frame.
For multiple sample-rate input, the tag bit for each input slot indicates whether valid data is
present.
For slot 1, the audio input frame’s status address port delivers codec control register read address
and multiple sample-rate slot request flags for all output slots. AC97 defines the ten least
significant bits as on-demand data request flags for output slots 3-12. For two-channel audio,
codec-only data-request flags corresponding to slots 3 and 4 are meaningful.
Audio input frame slot 1 tag bit pertains to status address port data. SLOTREQ bits are always
valid independent of the slot 1 tag bit.
Table 13-5. Input Slot 1 Bit Definitions
Bit Description
19 RESERVED (Filled with zero)
18-12 Control register Index (Filled with zeroes if AC97 tags it invalid)
11 Slot 3 request: PCM Left channel
10 Slot 4 request: PCM Right channel
9 Slot 5 request: Modem Line 1
8 Slot 6 request: NA
7 Slot 7 request: NA
6 Slot 8 request: NA
5 Slot 9 request: NA
4 Slot 10 request: NA
3 Slot 11 request: NA
2 Slot 12 request: NA
1,0 RESERVED (Filled with zero)