WM8804 datasheet(45/66 Pages) WOLFSON

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Production Data

WM8804

PD Rev 4.1 September 2007

AUDIO DATA FORMATS

Five interface formats are supported:

•

Left Justified Mode

•

Right Justified Mode

•

I2S Mode

•

DSP Mode A

•

DSP Mode B

The MSB is sent first in all formats. Word lengths of 16, 20 and 24 bits are supported.

Audio data for each stereo channel is clocked with the BCLK signal. Data is time multiplexed with the

LRCLK, indicating whether the left or right channel data is present. The LRCLK is also used as a

timing reference to indicate the beginning or end of the data words.

In Left Justified, Right Justified and I2S modes the minimum number of BCLKs per LRCLK period is

two times the number of bits in the selected word length. LRCLK must be high for a minimum of n

BCLKs and low for a minimum of n BCLKs, where n is the number of bits in an audio word. Any mark

to space ratio on LRCLK is acceptable provided the above requirements are met.

The data may also be output in DSP Mode A or Mode B, with LRCLK used as a frame sync to

identify the MSB of the first word. The minimum number of BCLKs per LRCLK period is two times the

number of bits in the word length.

LEFT JUSTIFIED MODE

In Left Justified mode, the MSB of DIN is sampled by the WM8804 on the first rising edge of BCLK

following an LRCLK transition. The MSB of the output data (DOUT) changes on the same falling

edge of BCLK as LRCLK and may be sampled on the next rising edge of BCLK. LRCLK is high

during the left samples and low during the right samples (Figure 18).

LEFT CHANNEL

RIGHT CHANNEL

LRCLK

BCLK

DIN / DOUT

1/fs

n-2 n-1

LSB

MSB

n-2 n-1

LSB

MSB

Figure 18 Left Justified Mode

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