WM8746

Production Data

w

March 2006, PD Rev 4.0

13

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.

LRCIN

BCKIN

DIN0

Input Word Length (IWL)

1/fs

CHANNEL 0

LEFT

n

2

1

n-1

LSB

MSB

n

2

1

n-1

CHANNEL 0

RIGHT

2

1

CHANNEL 1

LEFT

n

n-1

CHANNEL 2

RIGHT

NO VALID DATA

1

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.

LEFT CHANNEL

RIGHT CHANNEL

LRCIN

BCKIN

DIN0

2/fs

LSB

MSB

LSB

MSB

LEFT CHANNEL

RIGHT CHANNEL

n

2

1n

2

1n

2

1n

2

1

LSB

MSB

LSB

MSB

n

2

1

n

2

1

MSB

LSB

LSB

MSB

DIN1/2

LRCIN2

LEFT CHANNEL

RIGHT CHANNEL

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 I

2. The edges of LRCIN and LRCIN2 must be coincidental.