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PCM1870

SLAS544A – MAY 2007 – REVISED SEPTEMBER 2007

B15

B14

B13

B12

B11

B10

IDX6

IDX5

IDX4

IDX3

IDX2

IDX1

IDX0

RALC

RSV

RRTC

RATC

RCP1

RCP0

RLV1

RLV0

IDX[6:0]: 1010011b (53h) Register 83

RALC: Automatic Level Control (ALC) Enable for Recording

Default value: 0

Auto level control can be enabled with some parameters for microphone input or lower-level analog source.

RALC = 0

Disabled (default)

RALC = 1

Enabled

RRTC: ALC Recovery Time Control for Recording

Default value: 0

This bit selects the time during which a gain level change completes to compress the signal when the input to the

ADC increases in amplitude.

RRTC = 0

3.4 s (default)

RRTC = 1

13.6 s

RATC: ALC Attack Time Control for Recording

Default value: 0

This bit selects the time during which a gain level change completes to expand the signal when the input to the

ADC decreases in amplitude.

RATC = 0

1 ms (default)

RATC = 1

2 ms

RCP[1:0]: ALC Compression Level Control for Recording

Default value: 00

Auto level control can set the compression level to –2, –6, or –12 dB. Higher-level signals should be compressed

to avoid saturation or degradation of sound quality.

RCP[1:0]

ALC Compression Level Control for Recording

0 0

–2 dB (default)

0 1

–6 dB

1 0

–12 dB

1 1

Reserved

RLV[1:0]: ALC Expansion Level Control for Recording

Default value: 00

Auto level control can set the expansion level to 0, 6, 14, or 24 dB. Lower-level signals should be expanded to

make a small signal easy to hear. If set to 0 dB, the ALC can be operated only as a limiter.

RLV[1:0]

ALC Expansion Level Control for Recording

0 0

0 dB (default)

0 1

6 dB

1 0

14 dB

1 1

24 dB

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