CS4297 datasheet(25/46 Pages) CIRRUS

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DS242F5

CS4297

CrystalClear™ SoundFusion™ Audio Codec ’97

Stereo Analog Mixer Input Gain Registers (Index 10 - 18h)

These registers control the gain levels of the analog input sources to the Input Mixer. Each register step for

all registers corresponds to 1.5 dB gain adjustment, thus allowing a range of 12 dB to -34.5 dB of gain.

The MSB of these registers control an analog mute for each source to input mixer. Bits Gx4 - Gx0 of the

registers are used to control the gain levels for each source. The gain mapping for these bits is shown in

Table 3.

For the stereo source registers (10h through 18h), the default values are 8808h, corresponding to 0 dB at-

tenuation for both channels, and mute on.

Input Mux Select Register (Index 1Ah)

This register selects the input source to pass to the ADCs for capturing PCM data. The AC’97 specification

allows for independent control of the left and right channels for this mux. Bits SL2 - SL0 provide the de-

code for the left input mux, and bits SR2 - SR0 provide the decode for the right. Shown below are the pos-

sible values for each of these decodes:

The default power-on value for this register is 0000h, selecting the MIC inputs for both channels.

D15

D14

D13

D12

D11

D10

Mute

GL4

GL3

GL2

GL1

GL0

GR4

GR3

GR2

GR1

GR0

D15

D14

D13

D12

D11

D10

SL2

SL1

SL0

SR2

SR1

SR0

Gx4 - Gx0

Gain Level

00000

+12 dB

00001

+10.5 dB

……

00111

+1.5 dB

01000

0 dB

01001

-1.5 dB

……

11111

-34.5 dB

Table 3. Analog Mixer Input Gain Values

Sx2 - Sx0

Record Source

0MIC

CD Input

Video Input

AUX Input

Line Input

5Stereo Mix

Mono Mix

Phone Input

Table 4. Input Mux Selection Options

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