Pre-Production
WM8940
HI-FI DIGITAL TO ANALOGUE CONVERTER (DAC)
The DAC is enabled by the DACEN register bit.
REGISTER
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R3
0
DACEN
0
DAC enable
Power
Management 3
0 = DAC disabled
1 = DAC enabled
Table 30 DAC Enable
The WM8940 also has a Soft Mute function, which gradually attenuates the volume of the digital
signal to zero. When removed, the gain will step back up to the digital gain setting. This function is
disabled by default. To play back an audio signal, it must first be disabled by setting the DACMU bit
to zero.
REGISTER
ADDRESS
BIT
LABEL
DACMU
DEFAULT
DESCRIPTION
DAC soft mute enable
R10
DAC Control
6
0
0 = DACMU disabled
1 = DACMU enabled
Table 31 DAC Control Register
The digital audio data is converted to over sampled bit streams in the on-chip, true 24-bit digital
interpolation filters. The bit stream data enters a multi-bit, sigma-delta DAC, which converts it to a
high quality analogue audio signal. The multi-bit DAC architecture reduces high frequency noise and
sensitivity to clock jitter.
The DAC output defaults to non-inverted. Setting DACPOL will invert the DAC output phase.
AUTOMUTE
The DAC has an automute function which applies an analogue mute when 1024 consecutive zeros
are detected. The mute is released as soon as a non-zero sample is detected. Automute can be
enabled using the AMUTE control bit.
REGISTER
ADDRESS
BIT
LABEL
AMUTE
DEFAULT
DESCRIPTION
R10
DAC Control
2
0
DAC auto mute enable
0 = auto mute disabled
1 = auto mute enabled
Table 32 DAC Auto Mute Control Register
Pre-Production, Rev 3.0, February 2007
41
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
