CMI9738 Datasheet, PDF (13/36 Pages) List of Unclassifed Manufacturers – Integrated Multi-channel AC97

CMI 9738
Integrated Multi-channel AC‘97
Bit 19 4
Bit 3 0
Control Register Read Data
RESERVED
(Stuffed with 0’s if tagged “invalid”)
(Stuffed with 0’s)
If Slot 2 is tagged invalid by CMI9738, then the entire slot will be stuffed with 0’s.
Slot 3: PCM Record Left Channel
Audio input frame slot 3 is the left channel output of CMI9738 input MUX, post-ADC.
CMI9738 ADCs are implemented to support 18-bit resolution.
CMI9738 outputs its ADC data (MSB first), and stuffs any trailing non-valid bit positions
with 0's to fill out its 20-bit time slot.
Slot 4: PCM Record Right Channel
Audio input frame slot 4 is the right channel output of CMI9738 input MUX, post-ADC.
CMI9738 outputs its ADC data (MSB first), and stuffs any trailing non-valid bit positions
with 0's to fill out its 20-bit time slot.
Slot 5: Optional Modem Line 1 ADC
Audio input frame slots 5-12 are not used by the CMI9738 and are always stuffed with 0's.
4.6 AC-LINK AUDIO OUTPUT FRAME SDATA_OUT
The audio output frame data streams correspond to the multiplexed bundles of all digital output
data targeting the CMI9738 DAC inputs, and control registers. Each audio output frame supports
up to 12 20-bit outgoing data time slots. Slot 0 is a special reserved time slot containing 16 bits
that are used for AC-Link protocol infrastructure.
Within slot 0, the first bit is a global bit (SDATA_OUT slot 0, bit 15) which flags the validity for
the entire audio frame. If the “Valid Frame” bit is a 1, this indicates that the current audio frame
contains at least one slot time of valid data. The next 12 bit positions sampled by the CMI9738
indicate which of the corresponding 12 times slots contain valid data. In this way data streams of
differing sample rates can be transmitted across AC-Link at its fixed 48kHz audio frame rate. The
following diagram illustrates the time slot based AC-Link protocol.
Figure5 . AC-Link Audio Output Frame
C-MEDIA Electronics Inc.
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Revision Date Apr./2002
Revision 1.1