WM8805
Production Data
AUDIO DATA FORMATS
Five interface formats are supported:
•
•
•
•
•
Left Justified Mode
Right Justified Mode
I2S Mode
DSP Mode A
DSP Mode B
The MSB is sent first in all formats. Word lengths of 16, 20 and 24 bits are supported.
Audio data for each stereo channel is clocked with the BCLK signal. Data is time multiplexed with the
LRCLK, indicating whether the left or right channel data is present. The LRCLK is also used as a
timing reference to indicate the beginning or end of the data words.
In Left Justified, Right Justified and I2S modes the minimum number of BCLKs per LRCLK period is
two times the number of bits in the selected word length. LRCLK must be high for a minimum of n
BCLKs and low for a minimum of n BCLKs, where n is the number of bits in an audio word. Any mark
to space ratio on LRCLK is acceptable provided the above requirements are met.
The data may also be output in DSP Mode A or Mode B, with LRCLK used as a frame sync to
identify the MSB of the first word. The minimum number of BCLKs per LRCLK period is two times the
number of bits in the word length.
LEFT JUSTIFIED MODE
In Left Justified mode, the MSB of DIN is sampled by the WM8805 on the first rising edge of BCLK
following an LRCLK transition. The MSB of the output data (DOUT) changes on the same falling
edge of BCLK as LRCLK and may be sampled on the next rising edge of BCLK. LRCLK is high
during the left samples and low during the right samples (Figure 18).
1/fs
LEFT CHANNEL
RIGHT CHANNEL
LRCLK
BCLK
DIN / DOUT
1
2
3
n
n-2 n-1
1
2
3
n
n-2 n-1
MSB
LSB
MSB
LSB
Figure 18 Left Justified Mode
PD Rev 4.1 September 07
46
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
