WM8734 datasheet(27/46 Pages) WOLFSON

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WM8734

Production Data

PD Rev 4.1 November 2006

As a master mode device the WM8734 controls the sequencing of data transfer (ADCDAT,

DACDAT) and output of clocks (BCLK, ADCLRC, DACLRC) over the digital audio interface. It uses

the timing generated from either its on-board crystal or the MCLK input as the reference for the clock

and data transitions. This is illustrated in Figure 21. ADCDAT is always an output from and DACDAT

is always an input to the WM8734 independent of master or slave mode.

BCLK

ADCDAT

ADCLRC

DACDAT

DACLRC

WM8734

CODEC

DSP

ENCODER/

DECODER

Figure 21 Master Mode

As a slave device the WM8734 sequences the data transfer (ADCDAT, DACDAT) over the digital

audio interface in response to the external applied clocks (BCLK, ADCLRC, DACLRC). This is

illustrated in Figure 22.

BCLK

ADCDAT

ADCLRC

DACDAT

DACLRC

WM8734

CODEC

DSP

ENCODER/

DECODER

Figure 22 Slave Mode

Note that the WM8734 relies on controlled phase relationships between audio interface BCLK,

DACLRC and the master MCLK. To avoid any timing hazards, refer to the timing section for detailed

information.

AUDIO DATA SAMPLING RATES

The WM8734 provides for two modes of operation (normal and USB) to generate the required DAC

and ADC sampling rates. Normal and USB modes are programmed under software control according

to the table below.

In Normal mode, the user controls the sample rate by using an appropriate MCLK or crystal

frequency and the sample rate control register setting. The WM8734 can support sample rates from

8ks/s up to 96ks/s.

In USB mode, the user must use a fixed MLCK or crystal frequency of 12MHz to generate sample

rates from 8ks/s to 96ks/s. It is called USB mode since the common USB (Universal Serial Bus)

clock is at 12MHz and the WM8734 can be directly used within such systems. WM8734 can

generate all the normal audio sample rates from this one Master Clock frequency, removing the need

for different master clocks or PLL circuits.

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