Datasheet

58BCKs
CommandField
DID
LRCK
BCK
DI
DCO1,
DCI2
DeviceID=1
DeviceID=2
DCO1
DCO2,
DCI3
DCO29,
DCI30
DeviceID=3
DeviceID=30
TDMCA Frame
LRCK
BCK
DI
CMD
EMD EMD EMD
CMD
Don’t
Care
EMD
EMD
DO
Ch1
Ch(m)
Ch2
CMD
CMD Ch2 Ch3
Ch(n)
CMDCh1 Ch4
DI
Ch3
Ch4
[ForInitialization]
[ForOperation]
32Bits
DO
CMD
CMD CMD CMD CMD
CMD
1/f
S
Don’t
Care
PCM1795
SLES248 – MAY 2009 ........................................................................................................................................................................................................ www.ti.com
Figure 64. Device ID Determination Sequence
In general, the TDMCA frame consists of the command field, extended command (EMD) field, and audio data
fields. All fields are 32 bits in length, but the lowest byte has no meaning. The MSB is transferred first for each
field. The command field is always transferred as the first packet of the frame. The EMD field is transferred if the
EMD flag of the command field is high. If any EMD packets are transferred, no audio data follow the EMD
packets. This frame is for quick system initialization. All devices of a daisy-chain should respond to the command
field and extended command field. The PCM1795 has two audio channels that can be selected by OPE (register
19). If the OPE bit is not set to high, those audio channels are transferred. Figure 65 shows the general TDMCA
frame. If some DACs are enabled, but corresponding audio data packets are not transferred, the analog outputs
are unpredictable.
Figure 65. General TDMCA Frame
48 Submit Documentation Feedback Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): PCM1795