CS4281 Programming Manual
DS308PRM1
21
Confidential Draft
3/7/00
through the Playback SRC before being sent out
the AC Link.
The registers needed to setup a playback sequence
are enumerated in the Start-Up Configuration and
Status section. That section also enumerates global
CS4281 chip setup through both the PCI Start-Up
Configuration and the Sound-System Start-Up sec-
tions.
If the FM synthesizer is enabled and programmed
to generate sounds, the FM digital audio output will
be mixed with the data output from the Playback
SRC before being sent to the AC-Link engine.
The record data flow is depicted in Figure 7. The
audio data comes from the Codec, across the AC
Link, where the SSC moves the audio data into
FIFOn. The audio data comes from either the
AS-
DIN
pin for the primary Codec, or from the
ASDIN2
pin if a second Codec is present. The SSC gets a
signal from the AC-Link engine indicating that val-
id data for Slot y is available for transfer. The slot
valid bits for the input pins are set by the Codec it-
self. The SSC knows which FIFOn to connect to
Slot y via slot mapping IDs in the FIFOn FCRn
register. If the Record SRC is configured for the
same slot IDs as FIFOn, the audio stream is sent
through the Capture SRC before being loaded into
FIFOn.
On the other side of FIFOn, the DMAn engine con-
trols the data movement and configures the format-
ter for the data transfer. The formatter converts the
CS4281 internal 20-bit signed format to what ever
format is programmed for PC bus audio data trans-
fers (from the DMRn register). For record, FIFOn
sends a signal to the DMAn engine indicating
FIFOn is not empty. The DMAn engine responds
by acquiring the PCI bus and moving a sample
from FIFOn to host memory. The DMAn engine
continues moving samples until FIFOn is empty.
Anytime FIFOn becomes “not empty” the DMAn
reacquires the PCI bus and empties FIFOn. The
registers needed to setup a record sequence are
enumerated in the Start-Up Configuration and Sta-
tus section.
Capture
SRC
A
C
Li
nk E
ngi
ne
FIFOn
DMAn
DMRn
F
o
rm
atter
P
C
I
B
u
s
I
n
te
rf
a
c
e
FIFO not
empty
Slot x Valid
AC ’97
Codec
CS4281
Sound System
Controller
(SSC)
AC Link
Figure 7. Capture Data Flow Diagram
D
ra
ft
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