WM8958 Datasheet, PDF (106/377 Pages) Wolfson Microelectronics plc – Multi-Channel Audio Hub CODEC for Smartphones

WM8958
Pre-Production
AIF2 - INPUT PATH VOLUME CONTROL
The AIF2 interface supports two input channels. A digital volume control is provided on each input
signal path, allowing attenuation in the range -71.625dB to 0dB in 0.375dB steps. The level of
attenuation for an eight-bit code X is given by:
0.375  (X-192) dB for 1  X  192; MUTE for X = 0 0dB for 192  X  255
The AIF2DAC_VU bit controls the loading of digital volume control data. When AIF2DAC_VU bit is set
to 0, the AIF2DACL_VOL and AIF2DACR_VOL control data will be loaded into the respective control
register, but will not actually change the digital gain setting. Both left and right gain settings are
updated when a 1 is written to AIF2DAC_VU. This makes it possible to update the gain of left and
right channels simultaneously.
Note that a digital gain function is also available at the audio interface input, to boost the DAC volume
when a small signal is received on DACDAT2. See “Digital Audio Interface Control” for further details.
Digital volume control is also possible at the DAC stage of the signal path, after the audio signal has
passed through the DAC digital mixers. See “Digital to Analogue Converter (DAC)” for further details.
REGISTER
ADDRESS
R1282
(0502h)
AIF2 DAC
Left Volume
BIT
LABEL DEFAULT
8 AIF2DAC_V
N/A
U
7:0 AIF2DACL_
VOL [7:0]
C0h
(0dB)
R1283
(0503h)
8 AIF2DAC_V
U
AIF2 DAC
Right Volume
7:0 AIF2DACR_
VOL [7:0]
N/A
C0h
(0dB)
Table 51 AIF2 Input Path Volume Control
DESCRIPTION
AIF2DAC input path Volume Update
Writing a 1 to this bit will cause the AIF2DACL
and AIF2DACR volume to be updated
simultaneously
AIF2DAC (Left) input path Digital Volume
00h = MUTE
01h = -71.625dB
… (0.375dB steps)
C0h = 0dB
FFh = 0dB
(See Table 45 for volume range)
AIF2DAC input path Volume Update
Writing a 1 to this bit will cause the AIF2DACL
and AIF2DACR volume to be updated
simultaneously
AIF2DAC (Right) input path Digital Volume
00h = MUTE
01h = -71.625dB
… (0.375dB steps)
C0h = 0dB
FFh = 0dB
(See Table 45 for volume range)
AIF2 - INPUT PATH SOFT MUTE CONTROL
The WM8958 provides a soft mute function for each of the AIF2 interface input paths. When the soft-
mute function is selected, the WM8958 gradually attenuates the associated signal paths until the path
is entirely muted.
When the soft-mute function is de-selected, the gain will either return instantly to the digital gain
setting, or will gradually ramp back to the digital gain setting, depending on the
AIF2DAC_UNMUTE_RAMP register field.
The mute and un-mute ramp rate is selectable between two different rates.
The AIF2 input paths are soft-muted by default. To play back an audio signal, the soft-mute must first
be de-selected by setting AIF2DAC_MUTE = 0.
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PP, August 2012, Rev 3.4
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