CS4299-BQ datasheet(13/52 Pages) CIRRUS

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CS4299-BQ

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 CS4299-BQ 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 CS4299-BQ 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 CS4299-BQ (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

CS4299-BQ latches this data in, as the first bit of

the frame.

20.8

µs

(48 kHz)

Tag Phase

Data Phase

12.288 MHz

81.4 ns

SYNC

BIT_CLK

SDATA_OUT

SDATA_IN

F16

F15

F14

F13

F12

F35

F56

F76

D19

F255

Valid

Frame

Slot 1

Valid

R/W

WD15

F36

F57

D19

D18

D19

D18

D19

RD15

F16

F15

F14

F13

F12

F35

F56

F76

F255

F36

F57

F255

GPIO

INT

F96

D19

Slot 0

Slot 1

Slot 2

Slot 3

Slot 4

Slots 5-12

Slot 2

Valid

Slot 1

Valid

Slot 2

Valid

Codec

Ready

Slot 12

Valid

Codec

ID1

Codec

ID0

Slot 12

Valid

GPIO

INT

Bit Frame Position:

Figure 9. AC-link Input and Output Framing

CS4299-BQ Datasheet(PDF) 13 Page - Cirrus Logic

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