WM8746
Production Data
DSP MODE B
In DSP mode B, the first bit is sampled on the BCKIN edge which detects a low to high transition on
LRCIN.
1/fs
LRCIN
BCKIN
CHANNEL 0
LEFT
CHANNEL 0
RIGHT
CHANNEL 1
LEFT
CHANNEL 2
RIGHT
NO VALID DATA
1
2
n
1
2
n
1
2
n
1
DIN0
n-1
n-1
n-1
MSB
LSB
Input Word Length (IWL)
Figure 8 DSP Mode B Timing Diagram
In both DSP modes, DAC0 left is always sent first, followed immediately by data words for the other 5
channels. No BCKIN edges are allowed between the data words. The word order is DAC0 left, DAC0
right, DAC1 left, DAC1 right, DAC2 left, DAC2 right.
SPLIT RATE MODE
The WM8746 can be used with differing sample rates on the front and rear channels. This allows
extremely high quality audio to be played on the front two channels whilst the other channels use
normal high quality data streams.
This mode will only work with a front data rate of 192kHz and a rear rate of 96kHz but can be used
with all the normal data formats except the two DSP modes and with the system at either 128fs or
192fs see Table 4.
When running in split rate mode all the channels are clocked in using a common BCKIN; the front
channels using LRCIN and all the other channels using LRCIN2 see Figure 9.
2/fs
LEFT CHANNEL
LEFT CHANNEL
RIGHT CHANNEL
RIGHT CHANNEL
LRCIN
BCKIN
DIN0
1
2
n
1
2
n
1
2
n
1
2
n
LSB MSB
MSB
LSB MSB
MSB
LSB
LSB
LRCIN2
DIN1/2
LEFT CHANNEL
RIGHT CHANNEL
1
2
n
1
2
n
MSB
LSB
MSB
LSB
Figure 9 Split Rate Audio Mode Timing Diagram
Notes:
1. Figure 9 shows the timing for left justified however this is similar for right justified and I2S.
2. The edges of LRCIN and LRCIN2 must be coincidental.
March 2006, PD Rev 4.0
13
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
