CMI9738 Datasheet, PDF (11/36 Pages) List of Unclassifed Manufacturers – Integrated Multi-channel AC97

CMI 9738
Integrated Multi-channel AC‘97
SYNC remains high for a total duration of 16 BIT_CLKs at the beginning of each audio frame.
Theportion of the audio frame where SYNC is high is defined as the “Tag Phase”. The remainder
of theaudio frame where SYNC is low is defined as the “Data Phase”.
Additionally, for power savings, all clock, sync, and data signals can be halted.
4.5 AC-LINK AUDIO INPUT FRAME SDATA_IN
The audio input frame data streams correspond to the multiplexed bundles of all digital input data
targeting the AC 97 Controller. As is the case for audio output frame, each AC-link audio input
frame consists of 12, 20-bit timeslots. Slot 0 is a special reserved time slot containing 16-bits
which are used for AC-link protocol infrastructure.
Within slot 0 the first bit is a global bit (SDATA_IN slot 0, bit 15) which flags whether CMI9738
is in the “CodecReady” state or not. If the “Codec Ready” bit is a 0, this indicates thatCMI9738 is
not ready for normal operation. This condition is normal following the deassertion of power on
reset for example, while CMI9738’s voltage references settle. When the AC-link “Codec Ready”
indicator bit is a 1 it indicates that the AC-link and CMI9738 control and status registers are in a
fully operational state. The AC ‘97 Controller must further probe the Powerdown Control/Status
Register (section 6.3) to determine exactly which subsections, if any, are ready.
Prior to any attempts at putting CMI9738 into operation the AC ’97 Controller should poll the
first bit in the audio input frame (SDATA_IN slot 0, bit 15) for an indication that CMI9738 has
gone “Codec Ready”. Once CMI9738 is sampled “Codec Ready”8 then the next 12 bit positions
sampled by the AC ’97 Controller indicate which of the corresponding 12 time slots are assigned
to input data streams, and that they contain valid data. The following diagram illustrates the time
slot-based AC-link protocol.
Figure3. AC-link Audio Input Frame
C-MEDIA Electronics Inc.
6F, 100, Sec. 4, Civil Boulevard, Taipei, Taiwan, R.O.C. 106
TEL: [phone] FAX: [phone] E-mail:[e-mail]
Revision Date Apr./2002
Revision 1.1