WM8734 datasheet(21/42 Pages) ETC

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WM8734

Advanced Information

AI Rev 2.2 November 2001

In Master mode, DACLRC and ADCLRC will be output with a 50:50 mark-space ratio with BCLK

output at 64fs.

The ADC and DAC digital audio interface modes are software configurable as indicated in Table 7.

Note that dynamically changing the software format may result in erroneous operation of the

interfaces and is therefore not recommended. The length of the digital audio data is programmable at

16/20/24 or 32 bits. Refer to the software control table below. The data is signed 2’s complement.

Both ADC and DAC are fixed at the same data length. The ADC and DAC digital filters process data

using 24 bits. If the ADC is programmed to output 16 or 20 bit data then it strips the LSBs from the

24 bit data. If the ADC is programmed to output 32 bits then it packs the LSBs with zeros. If the DAC

is programmed to receive 16 or 20 bit data, the WM8734 packs the LSBs with zeros. If the DAC is

programmed to receive 32 bit data, then it strips the LSBs.

The DAC outputs can be swapped under software control using LRP and LRSWAP as shown in

Table 7. Stereo samples are normally generated as a Left/Right sampled pair. LRSWAP reverses the

order of that a Left sample goes to the right DAC output and a Right sample goes to the left DAC

output. LRP swaps the phasing so that a Right/Left sampled pair is expected and preserves the

correct channel phase difference.

To accommodate system timing requirements the interpretation of BCLK may be inverted, this is

controlled vias the software shown in Table 6. This is especially appropriate for DSP mode.

ADCDAT lines are always outputs. They power up and return from standby low.

DACDAT is always an input. It is expected to be set low by the audio interface controller when the

WM8734 is powered off or in standby.

ADCLRC, DACLRC and BCLK can be either outputs or inputs depending on whether the device is

configured as a master or slave. If the device is a master then the ADCLRC, DACLRC and BCLK

signals are outputs that default low. If the device is a slave then the ADCLRC, DACLRC and BCLK

are inputs.

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