wm8988 Wolfson Microelectronics plc, wm8988 Datasheet - Page 34

• Manufacturer Part Number: wm8988
• Description: Stereo Codec For Portable Audio Applications
• Manufacturer: Wolfson Microelectronics plc

WM8988
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DIGITAL AUDIO INTERFACE
The digital audio interface is used for inputting DAC data into the WM8988 and outputting ADC data
from it. It uses four pins:
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The clock signals BCLK and LRC can be an output when the WM8988 operates as a master, or an
input when it is a slave (see Master and Slave Mode Operation, below).
Four different audio data formats are supported:
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All four of these modes are MSB first. They are described in Audio Data Formats, below. Refer to the
Electrical Characteristic section for timing information.
MASTER AND SLAVE MODE OPERATION
The WM8988 can be configured as either a master or slave mode device. As a master device the
WM8988 generates BCLK, ADCLRC and DACLRC and thus controls sequencing of the data transfer
on ADCDAT and DACDAT. In slave mode, the WM8988 responds with data to clocks it receives over
the digital audio interface. The mode can be selected by writing to the MS bit (see Table 23). Master
and slave modes are illustrated below.
Figure 10 Master Mode
AUDIO DATA FORMATS
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.
Figure 12 Left Justified Audio Interface (assuming n-bit word length)
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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.
2
S mode, the MSB is available on the second rising edge of BCLK following a LRCLK transition.
ADCDAT: ADC data output
DACDAT: DAC data input
LRC: DAC and ADC data alignment clock
BCLK: Bit clock, for synchronisation
Left justified
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DSP mode
2
S
Figure 11 Slave Mode
PD, Rev 4.0, October 2008
Production Data
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