WM8988 Datasheet, PDF (37/56 Pages) Wolfson Microelectronics plc – Stereo CODEC for Portable Audio Applications

Production Data
WM8988
AUDIO INTERFACE CONTROL
The register bits controlling audio format, word length and master / slave mode are summarised in
Table 31. MS selects audio interface operation in master or slave mode. In Master mode BCLK and
LRC are outputs. The frequency of LRC is set by the sample rate control bits SR[4:0] and USB. In
Slave mode BCLK and LRC are inputs.
REGISTER
ADDRESS
R7 (07h)
Digital Audio
Interface
Format
BIT
LABEL
7
BCLKINV
6
MS
5
LRSWAP
4
LRP
3:2 WL[1:0]
1:0 FORMAT[1:0]
Table 31 Audio Data Format Control
DEFAULT
DESCRIPTION
0
BCLK invert bit (for master and slave
modes)
0 = BCLK not inverted
1 = BCLK inverted
0
Master / Slave Mode Control
1 = Enable Master Mode
0 = Enable Slave Mode
0
Left/Right channel swap
1 = swap left and right DAC data in
audio interface
0 = output left and right data as normal
0
right, left and i2s modes – LRCLK
polarity
1 = invert LRCLK polarity
0 = normal LRCLK polarity
DSP Mode – mode A/B select
1 = MSB is available on 1^st BCLK rising
edge after LRC rising edge (mode B)
0 = MSB is available on 2^nd BCLK rising
edge after LRC rising edge (mode A)
10
Audio Data Word Length
11 = 32 bits (see Note)
10 = 24 bits
01 = 20 bits
00 = 16 bits
10
Audio Data Format Select
11 = DSP Mode
10 = I²S Format
01 = Left justified
00 = reserved (do not use this setting)
AUDIO INTERFACE OUTPUT TRISTATE
Register bit TRI, register 24(18h) bit[3] can be used to tristate the ADCDAT pin and switch ADCLRC,
DACLRC and BCLK to inputs. In Slave mode (MASTER=0) LRC and BCLK are by default configured
as inputs and only ADCDAT will be tri-stated, (see Table 32).
REGISTER BIT LABEL DEFAULT
ADDRESS
DESCRIPTION
R24(18h)
Additional
Control (2)
3
TRI
0
Tristates ADCDAT and switches ADCLRC,
DACLRC and BCLK to inputs.
0 = ADCDAT is an output, LRC and BCLK are
inputs (slave mode) or outputs (master mode)
1 = ADCDAT is tristated, LRC and BCLK are
inputs
Table 32 Tri-stating the Audio Interface
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PD, Rev 4.0, October 2008
37