wm8987 Wolfson Microelectronics plc, wm8987 Datasheet - Page 40

• Manufacturer Part Number: wm8987
• Description: Stereo Codec For Portable Audio Applications
• Manufacturer: Wolfson Microelectronics plc

WM8987L
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MASTER MODE ADCLRC AND DACLRC ENABLE
In Master mode, by default ADCLRC is disabled when the ADC is disabled and DACLRC is disabled
when the DAC is disabled. Register bit LRCM, register 24(18h) bit[2] changes the control so that the
ADCLRC and DACLRC are disabled only when ADC and DAC are disabled. This enables the user to
use e.g. ADCLRC for both ADC and DAC LRCLK and disable the ADC when DAC only operation is
required, (see Table 34).
Table 34 ADCLRC/DACLRC Enable
BIT CLOCK MODE
The default master mode bit clock generator produces a bit clock frequency based on the sample
rate and input MCLK frequency as shown in Table 38. When enabled by setting the appropriate
BCM[1:0] bits, the bit clock mode (BCM) function overrides the default master mode bit clock
generator to produce the bit clock frequency shown in the table below:
Table 35 Master Mode BCLK Frequency Control
The BCM mode bit clock generator produces 16 or 24 bit clock cycles per sample. The number of bit
clock cycles per sample in this mode is determined by the word length bits (WL[1:0]) in the Digital
Audio Interface Format register (R7). When these bits are set to 00, there will be 16 bit clock cycles
per sample. When these bits are set to 01, 10 or 11, there will be 24 bit clock cycles per sample.
Please refer to Figure 19.
The BCM generator uses the ADCLRC signal, hence the ADCLRC signal must be enabled when
using bit clock mode. To enable the ADCLRC signal, either the ADC must be powered up or, if the
ADC is not in use, the LRCM bit must be set to enable both the ADCLRC and DACLRC signals when
either the ADC or the DAC is enabled.
When the BCM function is enabled, the following restrictions apply:
1. The DAC and ADC must be operated at the same sample rate.
2. DSP late digital audio interface mode is not available and must not be enabled.
Figure 19 Bit Clock Mode
R24(18h)
Additional
Control (2)
R8 (08h)
Clocking and
Sample Rate
Control
REGISTER
REGISTER
ADDRESS
ADDRESS
BIT
BIT
8:7
2
BCM[1:0]
LABEL
LABEL
LRCM
DEFAULT
DEFAULT
00
0
Selects disable mode for ADCLRC and
DACLRC
0 = ADCLRC disabled when ADC (Left and
1 = ADCLRC and DACLRC disabled only when
BCLK Frequency
00 = BCM function disabled
01 = MCLK/4
10 = MCLK/8
11 = MCLK/16
Right) disabled, DACLRC disabled when
DAC (Left and Right) disabled.
ADC (Left and Right) and DAC (Left and
Right) are disabled.
DESCRIPTION
DESCRIPTION
PD Rev 4.0 August 2008
Production Data
40