WM8956 datasheet(27/80 Pages) WOLFSON

27 / 80 page

Preliminary Technical Data

WM8956

PTD, July 2007, Rev 2.1

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

DACVU

DAC Volume Update

0 = Store LDACVOL in intermediate

latch (no gain change)

1 = Update left and right channel

gains (left = LDACVOL, right =

intermediate latch)

R10 (0Ah)

Left Channel

Digital Volume

7:0

LDACVOL

[7:0]

11111111

( 0dB )

Left DAC Digital Volume Control

0000 0000 = Digital Mute

0000 0001 = -127dB

0000 0010 = -126.5dB

... 0.5dB steps up to

1111 1111 = 0dB

DACVU

DAC Volume Update

0 = Store RDACVOL in intermediate

latch (no gain change)

1 = Update left and right channel

gains (left = intermediate latch, right

= RDACVOL)

R11 (0Bh)

Right Channel

Digital Volume

7:0

RDACVOL

[7:0]

11111111

( 0dB )

Right DAC Digital Volume Control

similar to LDACVOL

Table 9 Digital Volume Control

DAC SOFT MUTE AND SOFT UN-MUTE

The WM8956 also has a soft mute function, which, when enabled, gradually attenuates the volume of

the digital signal to zero. When soft mute is disabled, the gain will either gradually ramp back up to

the digital gain setting, or return instantly to the digital gain setting, depending on the DACSMM

The DAC is soft-muted by default. To play back an audio signal, this function must first be disabled

by setting the DACMU bit to zero.

DACSMM would typically be enabled when using soft mute during playback of audio data so that

when soft mute is then disabled, the sudden volume increase will not create pop noise by jumping

immediately to the previous volume level (e.g. resuming playback after pausing during a track).

DACSMM would typically be disabled when un-muting at the start of a digital music file, so that the

first part of the track is not attenuated (e.g. when starting playback of a new track, or resuming

playback after pausing between tracks).

DAC muting and un-muting using volume control bits

LDACVOL and RDACVOL.

DAC muting and un-muting using soft mute bit DACMU.

Soft un-mute not enabled (DACSMM = 0).

DAC muting and un-muting using soft mute bit DACMU.

Soft un-mute enabled (DACSMM = 1).

Figure 12 DAC Mute Control

The volume ramp rate during soft mute and un-mute is controlled by the DACMR bit. Ramp rates of

fs/32 and fs/2 are selectable as shown in Table 10 (fs = DAC sample rate).

WM8956 Datasheet(PDF) 27 Page - Wolfson Microelectronics plc

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