Datasheet

LRCK
BCK
DI
Don’t
Care
Ch1
Ch2 Ch3Ch1 Ch4
INandOUTChannelOrdersareCompletelyIndependent
DO
7Packets 32Bits´
Ch5 Ch6
1/f (256BCKClocks)
S
Ch2
CMDCMD
CMD
Command Field
31
Command
30 29 2328 24 22 15 716 8 0
DID EMD DCS
R/
W
DeviceID
RegisterID
Data NotUsed
PCM1795
www.ti.com ........................................................................................................................................................................................................ SLES248 – MAY 2009
Figure 66. TDMCA Frame Example of Six-Channel DAC and Two-Channel ADC With Command Read
The normal command field is defined as shown in Figure 67 . When the DID bit (MSB) is '1', this frame is used
only for device ID determination, and all remaining bits in the field are ignored.
Figure 67. Normal Command Field
Bit 31: Device ID enable flag
The PCM1795 operates to get its own device ID for TDMCA initialization if this bit is high.
Bit 30: Extended command enable flag
The EMD packet is transferred if this bit is high; otherwise, it is skipped. Once this bit is high, this frame does not
contain any audio data. This is for system initialization.
Bit 29: Daisy-chain selection flag
A high setting designates OUT-chain devices, low designates IN-chain devices. The PCM1795 is an IN device,
so the DCS bit must be set low.
Bits[28:24]: Device ID
The device ID is five bits in length and it can be defined. These bits identify the order of a device in the IN or
OUT daisy-chain. The top of the daisy-chain defines device ID 1 and successive devices are numbered 2, 3, 4,
etc. All devices for which the DCI is fixed high are also defined as ID 1. The maximum device ID is 30 each in
the IN and OUT chains. If a device ID of 0x1F is used, all devices are selected as broadcast when in the write
mode. If a device ID of 0x00 is used, no device is selected.
Bit 23: Command Read/Write flag
If this bit is high, the command is a read operation.
Bits[22:16]: Register ID
The register ID is seven bits in length.
Bits[15:8]: Command data
The command data are eight bits in length. Any valid data can be chosen for each register.
Bits[7:0]: Not used
These bits are never transported when a read operation is performed.
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Product Folder Link(s): PCM1795