WM8731 Wolfson Microelectronics Ltd., WM8731 Datasheet - Page 37

• Manufacturer Part Number: WM8731
• Description: WM8731 : Low Power Audio Codec With Integrated Headphone Driver
• Manufacturer: Wolfson Microelectronics Ltd.

WM8731
AUDIO DATA SAMPLING RATES
As a master mode device the WM8731 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 29. ADCDAT is always an output from and DACDAT
is always an input to the WM8731 independent of master or slave mode.
Figure 29 Master Mode
As a slave device the WM8731 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 30.
Figure 30 Slave Mode
Note that the WM8731 relies on controlled phase relationships between audio interface BCLK,
DACLRC and the master MCLK or CLKOUT. To avoid any timing hazards, refer to the timing section
for detailed information.
The WM8731 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 WM8731 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 WM8731 can be directly used within such systems. WM8731 can
generate all the normal audio sample rates from this one Master Clock frequency, removing the need
for different master clocks or PLL circuits.
Note: ADC and DAC can run at different rates
Note: The ADC and DAC can run at different rates
WM8731
CODEC
WM8731
CODEC
ADCLRC
ADCDAT
DACLRC
DACDAT
ADCLRC
ADCDAT
DACLRC
DACDAT
BCLK
BCLK
ENCODER/
DECODER
ENCODER/
DECODER
DSP
DSP
AI Rev 2.3 August 2001
Advanced Information
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