CS4297A Datasheet, PDF (13/52 Pages) Cirrus Logic – CrystalClear SoundFusion Audio Codec 97

CS4297A
3. AC LINK FRAME DEFINITION
The AC-link is a bidirectional serial port with data
organized into frames consisting of one 16-bit and
twelve 20-bit time-division multiplexed slots. The
first slot, called the tag slot, contains bits indicating
if the CS4297A is ready to receive data (input
frame) and which, if any, other slots contain valid
data. Slots 1 through 12 contain audio or con-
trol/status data. Both the serial data output and in-
put frames are defined from the controller
perspective, not from the CS4297A perspective.
The controller synchronizes the beginning of a
frame with the assertion of the SYNC signal.
Figure 9 shows the position of each bit location
within the frame. The first bit position in a new se-
rial data frame is F0 and the last bit position in the
serial data frame is F255. When SYNC goes active
(high) and is sampled active by the CS4297A (on
the falling edge of BIT_CLK), both devices are
synchronized to a new serial data frame. The data
on the SDATA_OUT pin at this clock edge is the
final bit of the previous frame’s serial data. On the
next rising edge of BIT_CLK, the first bit of Slot 0
is driven by the controller on the SDATA_OUT
pin. On the next falling edge of BIT_CLK, the
CS4297A latches this data in, as the first bit of the
frame.
Tag Phase
SYNC
BIT_CLK
12.288 MHz
81.4 ns
20.8 µ s
(48 kHz)
Data Phase
Bit Frame Position: F255
SDATA_OUT 0
F0
Valid
Frame
F1
Slot 1
Valid
F2
Slot 2
Valid
F12
F13
Slot 12
Valid
0
F14
Codec
ID1
F15
Codec
ID0
F16
R/W
F35
F36
0 WD15
F56
F57
D19 D18
F76
D19
F96
F255
D19
0
Bit Frame Position:
SDATA_IN
F255
GPIO
INT
F0
Codec
Ready
F1
Slot 1
Valid
F2
Slot 2
Valid
F12
F13
F14 F15
F16
Slot 12
0
0
Valid
0
0
F35
F36
0 RD15
F56 F57
D19 D18
F76
D19
F96
D19
F255
GPIO
INT
Slot 0
Slot 1
Slot 2
Slot 3
Figure 9. AC-link Input and Output Framing
Slot 4
Slots 5-12
13