PCM1795 datasheet(49/58 Pages) TI

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LRCK

BCK

Don’t

Care

Ch1

Ch2

Ch3

Ch1

Ch4

INandOUTChannelOrdersareCompletelyIndependent

7Packets

32Bits

Ch5

Ch6

1/f (256BCKClocks)

Ch2

CMD

Command Field

Command

DID

EMD

DCS

R/W

DeviceID

RegisterID

Data

NotUsed

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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