CS4297 datasheet(26/46 Pages) CIRRUS

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DS242F5

CS4297

CrystalClear™ SoundFusion™ Audio Codec ’97

Record Gain Register (Index 1Ch)

This register controls the input gain on the analog source which is applied after the input mux and before

the ADCs. The 4-bit value allows for 0 dB to +22.5 dB of gain in 1.5 dB steps. The most significant bit of

the register controls an analog Mute which mutes the signal prior to the ADCs. The following table shows

the possible gain values available:

The default value for this register is 8000h, which corresponds to 0 dB gain with mute on.

Record Gain Mix (Index 1Eh)

The CS4297 does not support the optional 3rd ADC for the MIC PCM input. The Record Gain Mix register

has no function in The CS4297. Writes to this register are ignored, and reads from this register will always

return 0000h.

General Purpose Register (Index 20h)

This register controls miscellaneous facets of the CS4297 mixer. The only bits which have defined func-

tions in the CS4297 are the MIX, MS, and LPBK bits. The MIX bit selects which data to send to the Mono

Output Path. A ‘cleared’ value enables the Mono Mix out (a mix of the 5 analog stereo sources plus

PCM_OUT), while a ‘set’ value passes the MIC to the output. The MS (Mic Select) bit determines which

of the 2 MIC inputs are passed to the rest of the mixer. A ‘cleared’ value selects the MIC1 input, while a

‘set’ value selects the MIC2 input. The LPBK bit enables ADC/DAC Loopback Mode which is used to

facilitate performance evaluation of the CS4297.

D15

D14

D13

D12

D11

D10

Mute

GL3

GL2

GL1

GL0

GR3

GR2

GR1

GR0

D15

D14

D13

D12

D11

D10

MIX

LPBK

00000

Gx3 - Gx0

Gain

1111

+22.5 dB

0000

0 dB

Table 5. Input Mux Selection Options

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