WM8771 datasheet(26/44 Pages) WOLFSON

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WM8771

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PP Rev 2.0 December 2001

Figure 21 shows the application and release of MUTE whilst a full amplitude sinusoid is being played

at 48kHz sampling rate. When MUTE (lower trace) is asserted, the output (upper trace) begins to

decay exponentially from the DC level of the last input sample. The output will decay towards VMID

with a time constant of approximately 64 input samples. If MUTE is applied to all channels for 1024

or more input samples the outputs will be connected directly to Vmid, if IZD is set. When MUTE is

de-asserted, the output will restart immediately from the current input sample.

Note that all other means of muting the DAC channels: setting the PL[3:0] bits to 0, setting the

PDWN bit or setting attenuation to 0 will cause much more abrupt muting of the output.

Each ADC channel also has an individual mute control bit, which mutes the input to the ADC. In

addition both channels may be muted by setting ADCMUTE.

BIT

LABEL

DEFAULT

DESCRIPTION

11001

ADC Mute

ADCMUTE

ADC MUTE Left and Right

0 : Normal Operation

1: mute ADC left and ADC right

11001

ADC Mute Left

MUTE

ADC Mute select

0 : Normal Operation

1: mute ADC left

11010

ADC Mute Right

MUTE

ADC Mute select

0 : Normal Operation

1: mute ADC right

The Record outputs may be enabled by setting RECEN[2:0], where RECEN[0] mutes the REC1L and

REC1R outputs, RECEN[1] mutes the REC2L and REC2R outputs and RECEN[2] mutes the REC3L

and REC3R outputs.

BIT

LABEL

DEFAULT

DESCRIPTION

10100

REC Enable

[7:5]

RECMUTE[2:0]

000

REC Output Enable

0 : REC output disabled

1: REC output enabled

DE-EMPHASIS MODE

A digital De-emphasis filter may be applied to each DAC channel. The De-emphasis filter for each

stereo channel is enabled under the control of DEEMP[3:0]. DEEMP[0] enables the de-emphasis

filter for channel 1, DEEMP[1] enables the de-emphasis filter for channel 2, DEEMP[2] enables the

de-emphasis filter for channel 3 and DEEMP[3] enables the de-emphasis filter for channel 4.

BIT

LABEL

DEFAULT

DESCRIPTION

10101

DAC De-emphasis

Control

[3:0]

DEEMPH[3:0]

0000

De-emphasis mode select:

0 : Normal Mode

1: De-emphasis Mode

Refer to Figure 29, Figure 30, Figure 31, Figure 32, Figure 33 and Figure 34 for details of the De-

Emphasis modes at different sample rates.

POWERDOWN MODE AND ADC/DAC DISABLE

Setting the PDWN register bit immediately powers down the WM8771. All trace of the previous input

samples are removed, but all control register settings are preserved. When PDWN is cleared the

digital filters will be reinitialised. . It is recommended that the 8-channel input mux and buffer, ADC,

DAC and output buffers are powered down before setting PDWN.

BIT

LABEL

DEFAULT

DESCRIPTION

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