WM8778 datasheet(17/50 Pages) WOLFSON

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WM8778

PP Rev 1.7 June 2004

ADCBCLK

DOUT

ADCLRC

DIN

DACLRC

WM8778

CODEC

DVD

Controller

DACBCLK

Figure 11 Master Mode

AUDIO INTERFACE FORMATS

Audio data is applied to the internal DAC filters or output from the ADC filters, via the Digital Audio

Interface. 5 popular interface formats are supported:

•

Left Justified mode

•

Right Justified mode

•

2S mode

•

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

2S modes, the digital audio interface receives DAC data on the DIN

input and outputs ADC data on DOUT. Audio Data for each stereo channel is time multiplexed with

ADCLRC/DACLRC indicating whether the left or right channel is present. ADCLRC/DACLRC is also

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

In left justified, right justified and I

2S modes; the minimum number of BCLKs per DACLRC/ADCLRC

period is 2 times the selected word length. ADCLRC/DACLRC 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/DACLRC is acceptable provided the above requirements are met.

In DSP early or DSP late mode, DACLRC is used as a frame sync signal to identify the MSB of the

first word. The minimum number of DACBCLKs per DACLRC period is 2 times the selected word

length. Any mark to space ratio is acceptable on DACLRC provided the rising edge is correctly

positioned. The ADC data may also be output in DSP early or late modes, with ADCLRC used as a

frame sync to identify the MSB of the first word. The minimum number of ADCBCLKs per ADCLRC

period is 2 times the selected word length.

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