WM8750JL
Production Data
BCLK
ADCLRC
DACLRC
ADCDAT
DACDAT
DSP
ENCODER/
DECODER
WM8750JL
CODEC
Note: The ADC and DAC can run at different sample rates
Figure 16 Master Mode
Figure 17 Slave Mode
Note: For optimum ADC audio performance in slave mode, the BCLK input signal should be
configured to transition at the same time as the falling edge of MCLK.
The ADCDAT digital data output is buffered inside the CODEC using a digital logic buffering block.
However, the ADCDAT buffering block is not reset by the power-on reset circuit and hence the
ADCDAT pin stage (logic high or logic low) is undefined at power up until data is clocked out from the
ADC. Implementation of either of these workarounds will ensure correct operation:
Ensure that any external connection to the ADCDAT pin is made with the understanding
that ADCDAT pin may be driven high or low by the CODEC until ADC data is clocked out.
Tri-state the ADCDACDAT output pin by setting the TRI bit in R24 (Additional Control 2
register). Setting this bit will also configure ADCLRC, DACLRC and BCLK as inputs and (as
the CODEC has no internal pull-up/down resistors) the input voltage level must be set on
these pins by an external source (either the device connected to the digital audio interface
or pull-up/down resistors) to prevent excess current consumption.
AUDIO DATA FORMATS
In I2S mode, the MSB is available on the second rising edge of BCLK following a LRCLK transition.
The other bits up to the LSB are then transmitted in order. Depending on word length, BCLK
frequency and sample rate, there may be unused BCLK cycles between the LSB of one sample and
the MSB of the next.
Figure 18 I2S Audio Interface Format (assuming n-bit word length)
In Left Justified mode, the MSB is available on the first rising edge of BCLK following a LRCLK
transition. The other bits up to the LSB are then transmitted in order. Depending on word length,
BCLK frequency and sample rate, there may be unused BCLK cycles before each LRCLK transition.
PD, April 2012, Rev 4.1
38
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
