WM8775

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PP Rev 1.8, June 2004

16

AUDIO INTERFACE FORMATS

Audio data output from the ADC filters, via the Digital Audio Interface. 5 popular interface formats are

supported:

•

Left Justified mode

•

Right Justified mode

•

I

•

DSP Early mode

•

DSP Late mode

All 5 formats send the MSB first and support word lengths of 16, 20, 24 and 32 bits, with the

exception of 32 bit right justified mode, which is not supported.

In left justified, right justified and I

Audio Data for each stereo channel is time multiplexed with ADCLRC indicating whether the left or

right channel is present. ADCLRC is also used as a timing reference to indicate the beginning or end

of the data words.

In left justified, right justified and I

times the selected word length. ADCLRC must be high for a minimum of word length BCLKs and low

for a minimum of word length BCLKs. Any mark to space ratio on ADCLRC is acceptable provided

the above requirements are met.

In DSP early or DSP late mode, the ADC data may also be output, with ADCLRC used as a frame

sync to identify the MSB of the first word. The minimum number of BCLKs per ADCLRC period is 2

times the selected word length

LEFT JUSTIFIED MODE

In left justified mode, the MSB of the ADC data is output on DOUT and changes on the same falling

edge of BCLK as ADCLRC and may be sampled on the rising edge of BCLK. ADCLRC is high during

the left samples and low during the right samples (Figure 12).

LEFT CHANNEL

RIGHT CHANNEL

ADCLRC

BCLK

DOUT

1/fs

n

3

2

1

n-2 n-1

LSB

MSB

n

3

2

1

n-2 n-1

LSB

MSB

Figure 12 Left Justified Mode Timing Diagram

RIGHT JUSTIFIED MODE

In right justified mode, the LSB of the ADC data is output on DOUT and changes on the falling edge

of BCLK preceding a ADCLRC transition and may be sampled on the rising edge of BCLK. ADCLRC

is high during the left samples and low during the right samples (Figure 13).