CS4299-BQ_06 Datasheet, PDF (16/52 Pages) Cirrus Logic – CrystalClear SoundFusion Audio Codec 97

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3.2 AC-Link Audio Input Frame
In the serial data input frame, data is passed on the SDATA_IN pin from the CS4299-BQ to the AC ’97
controller. The data format for the input frame is very similar to the output frame. Figure 9 on page 13 il-
lustrates the serial port timing.
The PCM capture data from the CS4299-BQ 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 truncate) to the desired bit depth.
Bits that are reserved or not implemented in the CS4299-BQ will always be returned ‘cleared’.
3.2.1 Serial Data Input Slot Tag Bits (Slot 0)
Bit 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
Codec Slot 1 Slot 2 Slot 3 Slot 4 Slot 5 Slot 6 Slot 7 Slot 8 Slot 9 Slot 10
Ready Valid Valid Valid Valid Valid Valid Valid Valid Valid Valid
0
0
0
0
0
Codec Ready
The Codec Ready bit indicates the readiness of the CS4299-BQ AC-link. Immediately after a
Cold Reset this bit will be ‘clear’. Once the CS4299-BQ 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 Reg-
ister (Index 26h) by the controller before any access is made to the mixer registers. Any ac-
cesses to the CS4299-BQ 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-BQ ADCs. Only if a Slot [3:10] Valid bit is ‘set’ will the corresponding input slot con-
tain valid data.
3.2.2 Status Address Port (Slot 1)
Bit 19 18 17 16 15 14 13 12 11 10 9
8
7
6
5
4
3
0 RI6 RI5 RI4 RI3 RI2 RI1 RI0 SR3 SR4 SR5 SR6 SR7 SR8 SR9 SR10 0
210
Reserved
RI[6:0]
SR[3:10]
16
16
Register Index. The RI[6:0] bits echo the AC ’97 register address when a register read has
been requested in the previous frame. The CS4299-BQ will only echo the register index for
a read access. Write accesses will not return valid data in Slot 1.
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.
DS319-BQPP2