Crystal CS4281, Programming Manual

Page: 60 / 231

Confidential Draft 3/7/00
CS4281 Programming Manual
60 DS308PRM1
8.2.3 6-Channel Dual-Codec Playback
Setup Example
The following example, illustrated in Figure 16,
describes the codec register configuration needed
for a dual-codec system where the primary codec is
a standard AC ‘97 codec, such as the
CS4297/CS4297A, and the secondary codec is a
quad-channel CS4294. The primary codec supports
the standard stereo output stream and the secondary
codec supports the other four channels. The Sound
System Start-Up and the Sound System Playback
sections describe how to set-up the CS4281. The
CS4281 must be configured to use three streams
where AC-Link slots 3 and 4 are left and right
channels, slots 7 and 8 are left and right surround
channels, and slots 6 and 9 are center and LFE
channels. Three CS4281 FIFOs must be mapped to
the above mentioned slot pairs and the appropriate
six output slot valid bits (ACOSV) must be set
when everything else is configured. The following
list describes what registers inside the AC ‘97 co-
decs need to be configured to support playback of
6-channels (3 streams) through the two codecs.
• Make sure primary codec (CS4297/CS4297A)
is ready;
ACSTS.CRDY
set
• Make sure calibration finished; Read primary
codec Index 26h,
REF
=
ANL
=
DAC
= 1
• If
ACSTS.VSTS
set, read ACSAD and
ACSDA to clear
VSTS
• Write Command register index; ACCAD =
0026h
• Send read request down AC Link; Set
ACCTL.CRW
and
ACCTL.DCV
• When
ACSTS.VSTS
set, read ACSAD = 26h
(index) and ACSDA = xxxEh/xxxFh (
REF
,
ANL
,
DAC
set)
• Unmute and set volume for Slot 3/4 DACs;
Write primary codec Index 18h = 0808 (0 dB)
• Write Command register index; ACCAD =
0018h
• Write Data register; ACCDA = 0808h
• Send write request down AC link; Clear
ACCTL.CRW
, set
ACCTL.DCV
CS4281
AC Link
CS4297/
CS4297A
Line Out
CS4294
Line Out
ASDIN2
ASDIN
Left
Right
Alt-Line
Out
Surround Left
Surround Right
Center
LFE
Figure 16. 6-Channel Playback Block Diagram
D
ra
ft