CS4299 datasheet(16/52 Pages) CIRRUS

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CS4299

3.2

AC-Link Audio Input Frame

In the serial data input frame, data is passed on the SDATA_IN pin from the CS4299 to the AC ’97 con-

troller. The data format for the input frame is very similar to the output frame. Figure 9 on page 13 illus-

trates the serial port timing.

The PCM capture data from the CS4299 is shifted out MSB first in the most significant 18 bits of each slot.

The least significant 2 bits in each slot will be ‘cleared’. If the host requests PCM data from the AC ’97

Controller that is less than 18 bits wide, the controller should dither and round or just round (but not trun-

cate) to the desired bit depth.

Bits that are reserved or not implemented in the CS4299 will always be returned ‘cleared’.

3.2.1

Serial Data Input Slot Tag Bits (Slot 0)

Codec Ready

The Codec Ready bit indicates the readiness of the CS4299 AC-link. Immediately after a Cold

Reset this bit will be ‘clear’. Once the CS4299 clocks and voltages are stable, this bit will be

‘set’. Until the Codec Ready bit is ‘set’, no AC-link transactions should be attempted by the

controller. The Codec Ready bit does not indicate readiness of the DACs, ADCs, Vref, or any

other analog function. Those must be checked in the Powerdown Control/Status Register (In-

dex 26h) by the controller before any access is made to the mixer registers. Any accesses to

the CS4299 while Codec Ready is ‘clear’ are ignored.

Slot 1 Valid

When ‘set’, the Slot 1 Valid bit indicates Slot 1 contains a valid read back address.

Slot 2 Valid

When ‘set’, the Slot 2 Valid bit indicates Slot 2 contains valid register read data.

Slot [3:10] Valid

When ‘set’, the Slot [3:10] Valid bits indicate Slot [3:10] contains valid capture data from the

CS4299 ADCs. Only if a Slot [3:10] Valid bit is ‘set’ will the corresponding input slot contain

valid data.

3.2.2

Status Address Port (Slot 1)

RI[6:0]

been requested in the previous frame. The CS4299 will only echo the register index for a read

access. Write accesses will not return valid data in Slot 1.

SR[3:10]

Slot Request. If SRx is ‘set’, this indicates the CS4299 SRC does not need a new sample on

the next AC-link frame for that particular slot. If SRx is ‘clear’, the SRC indicates a new sample

is needed on the following frame. If the VRA bit in the Extended Audio Status/Control Register

(Index 2Ah) is ‘clear’, the SR[3:10] bits are always 0. When VRA is ‘set’, the SRC is enabled

and the SR[3:10] bits are used to request data.

Bit 15

543210

Codec

Ready

Slot 1

Valid

Slot 2

Valid

Slot 3

Valid

Slot 4

Valid

Slot 5

Valid

Slot 6

Valid

Slot 7

Valid

Slot 8

Valid

Slot 9

Valid

Slot 10

Valid

00000

Bit 19

3210

RI6

RI5

RI4

RI3

RI2

RI1

RI0

SR3 SR4 SR5 SR6 SR7 SR8 SR9 SR10

Reserved

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