WM8706

Production Data

w

PD Rev 4.1 July 2005

18

ATTENUATION CONTROL

Each DAC channel can be attenuated digitally before being applied to the digital filter. Attenuation is 0dB by default but can be

set between 0 and 127.5dB in 0.5dB steps using the 8 Attenuation control bits. All attenuation registers are double latched

allowing new values to be pre-latched to both channels before being updated synchronously. Setting the UPDATE bit on any

attenuation write will cause all pre-latched values to be immediately applied to the DAC channels.

REGISTER

ADDRESS

A2, A1, A0

BIT

LABEL

DEFAULT

DESCRIPTION

7:0

LAT[7:0]

11111111

(0dB)

Attenuation data for Left channel DACL in 0.5dB steps.

000

DACL

Attenuation

8

UPDATEL

0

Controls simultaneous update of all Attenuation Latches

0: Store DACL in intermediate latch (no change to output)

1: Store DACL and update attenuation on all channels.

7:0

RAT[7:0]

11111111

(0dB)

Attenuation data for Right channel DACR in 0.5dB steps.

001

DACR

Attenuation

8

UPDATER

0

Controls simultaneous update of all Attenuation Latches

0: Store DACR in intermediate latch (no change to output)

1: Store DACR and update attenuation on all channels.

Table 9 Attenuation Register Map

Note:

1.

The UPDATE bit is not latched. If UPDATE=0, the Attenuation value will be written to the pre-latch but not applied to the

relevant DAC. If UPDATE=1, all pre-latched values will be applied from the next input sample.

2.

Care should be used in reducing the attenuation as rapid large volume changes can introduce zipper noise.

DAC OUTPUT ATTENUATION

Registers LAT and RAT control the left and right channel attenuation. Table 10 shows how the

attenuation levels are selected from the 8-bit words.

XAT[7:0]

ATTENUATION LEVEL

00(hex)

∞dB (mute)

01(hex)

127.5dB

:

:

:

:

:

:

FE(hex)

0.5dB

FF(hex)

0dB

Table 10 Attenuation Control Levels

MUTE MODES

Setting the MUT register bit will apply a 'soft' mute to the input of the digital filters:

REGISTER ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

010

DAC Control

0

MUT

0

Soft Mute select

0 : Normal Operation

1: Soft mute all channels

Table 11 Mute Control

DE-EMPHASIS MODE

Setting the DEEMPH register bit puts the all the digital filters into de-emphasis mode:

REGISTER ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

010

DAC Control

1

DEEMPH

0

De-emphasis mode select:

0 : De-emphasis Off

1: De-emphasis On

Table 12 De-emphasis Control