Datasheet

Extended Command Field
31
ExtendedCommand
30 29 2328 24 22 15 716 8 0
RSVD EMD DCS
R/
W
DeviceID
RegisterID
Data NotUsed
Audio Fields
31
AudioData
12 716 8 0
MSB
24Bits
LSB All0s
4 3
TDMCA Register Requirements
Register Write/Read Operation
BCK
DI
DO
DOEN
(Internal)
1BCKEarly
Read ModeandProperRegisterID WriteDataRetrieved,ifWriteMode
ReadDataDriven,ifReadMode
RegisterIDPhase
DataPhase
PCM1795
SLES248 – MAY 2009 ........................................................................................................................................................................................................ www.ti.com
The extended command field is the same as the command field, except that it does not have a DID flag.
Figure 68 defines the extended command field.
Figure 68. Extended Command Field
The audio field is 32 bits in length and the audio data are transferred MSB first, so the other fields must be filled
with 0s as shown in Figure 69 .
Figure 69. Audio Field Example
The TDMCA mode requires device ID and audio channel information, as previously described. The OPE bit in
register 19 indicates audio channel availability and register 23 indicates the device ID. Register 23 is used only in
the TDMCA mode; see the mode control register map of Table 9 .
The command supports register write and read operations. If the command requests to read one register, the
read data are transferred on DO during the data phase of the timing cycle. The DI signal can be retrieved at the
positive edge of BCK, and the DO signal is driven at the negative edge of BCK. DO is activated one BCK cycle
early to compensate for the output delay caused by high impedance. Figure 70 shows the TDMCA write and
read timing.
Figure 70. TDMCA Write and Read Operation Timing
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