WM8978 Wolfson Microelectronics Ltd., WM8978 Datasheet - Page 65

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WM8978

Manufacturer Part Number
WM8978
Description
The WM8978 is a low power, high quality stereo codec designed for portable applications such as Digital still camera or Digital Camcorde
Manufacturer
Wolfson Microelectronics Ltd.
Datasheet

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Preliminary Technical Data
DIGITAL AUDIO INTERFACES
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The audio interface has four pins:
The clock signals BCLK, and LRC can be outputs when the WM8978 operates as a master, or inputs
when it is a slave (see Master and Slave Mode Operation, below).
Five different audio data formats are supported:
All 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 WM8978 audio interface may be configured as either master or slave. As a master interface
device the WM8978 generates BCLK and LRC and thus controls sequencing of the data transfer on
ADCDAT and DACDAT. To set the device to master mode register bit MS should be set high. In
slave mode (MS=0), the WM8978 responds with data to clocks it receives over the digital audio
interfaces.
AUDIO DATA FORMATS
In Left Justified mode, the MSB is available on the first rising edge of BCLK following an LRC
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 LRC transition.
Figure 33 Left Justified Audio Interface (assuming n-bit word length)
ADCDAT: ADC data output
DACDAT: DAC data input
LRC: Data Left/Right alignment clock
BCLK: Bit clock, for synchronisation
Left justified
Right justified
I
DSP mode A
DSP mode B
2
S
PTD Rev 2.6 November 2005
WM8978
65