DSD1796DBRG4 datasheet(43/61 Pages) TI1

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DSD1796

SLES101A – DECEMBER 2003 – REVISED NOVEMBER 2006

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Device ID Determination

The TDMCA mode also supports a multichip implementation in one system. This means a host controller (DSP) can

simultaneously support several TDMCA devices, which can be of the same type or different types, including PCM devices.

The PCM devices are categorized as IN device, OUT device, IN/OUT device, and NO device. The IN device has an input

port to receive audio data, the OUT device has an output port to supply audio data, the IN/OUT device has both input and

output ports for audio data, and the NO device has no port for audio data but needs command data from the host. A DAC

is an IN device, an ADC is an OUT device, a codec is an IN/OUT device, and a PLL is a NO device. The DSD1796 is an

IN device. For the host controller to distinguish the devices, each device is assigned its own device ID by the daisy chain.

The devices obtain their own device IDs automatically by connecting their DCI to the DCO of the preceding device and their

DCO to the DCI of the following device in the daisy chain. The daisy chains are categorized as the IN chain and the OUT

chain, which are completely independent and equivalent. Figure 50 shows an example daisy chain connection. If a system

needs to chain the DSD1796 and a NO device in the same IN or OUT chain, the NO device must be chained at the back

end of the chain because it does not require any audio data. Figure 51 shows an example of a TDMCA system including

an IN chain and an OUT chain with a TI DSP. For a device to get its own device ID, the DID signal must be set to 1 (see

the Command Field section for details), and LRCK and BCK must be driven in the TDMCA mode for all PCM devices which

are chained. The device at the top of the chain knows its device ID is 1 because its DCI is fixed HIGH. Other devices count

the BCK pulses and observe their own DCI signal to determine their position and ID. Figure 52 shows the initialization of

each device ID.

IN Device

OUT Device

OUT

IN/OUT

IN Chain

OUT Chain

IN Device

OUT Device

OUT

NO Device

Device

IN/OUT

Device

• • •

Figure 50. Daisy Chain Connection

DSD1796DBRG4 Datasheet(PDF) 43 Page - Texas Instruments