AD1981B

Rev. C | Page 16 of 32

MIC VOLUME REGISTER

Index 0x0E

Reg No.

Name

D15

D14

D13

D12

D11

D10

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

Default

0x0E

MIC Volume

MCM

X

X

X

X

X

X

X

X

M20

X

MCV4

MCV3

MCV2

MCV1

MCV0

0x8008

All registers are not shown, and bits containing an X are assumed to be reserved. Refer to Table 17 for examples.

Table 16.

Bit

Mnemonic

Function

MCV [4:0]

MIC Volume Gain

Allows setting the phone volume attenuator in 32 volume levels with 31 steps of 1.5 dB each. The LSB

represents 1.5 dB, and the gain range is +12 dB to −34.5 dB. The default value is 0 dB, with the mute bit

enabled.

M20

MIC Gain Boost

This bit allows setting additional MIC gain to increase the microphone sensitivity. The nominal gain

boost by default is 20 dB; however, Bits D0 and D1 (MBG [1:0]) on the miscellaneous control bits register

(0x76) allow changing the gain boost to 10 dB or 30 dB, if necessary.

0 = Disabled; Gain = 0 dB

1 = Enabled; Default Gain = 20 dB (see Register 0x76, Bits D0, D1)

MCM

MIC Mute

When this bit is set to 1, the MIC channel is muted.

Table 17. Volume Settings for Phone and MIC

Control Bits D [4:0] Phone (0x0C) and MIC (0x0E)

D15

Write

Readback

Function

0

0 0000

0 0000

12 dB Gain

0

0 1000

0 1000

0 dB Gain

0

1 1111

1 1111

−34.5 dB Gain

1

X XXXX

X XXXX

−∞ db Gain, Muted

X is a wild card, and has no effect on the value.

LINE-IN VOLUME REGISTER

Index 0x10

Reg No.

Name

D15

D14

D13

D12

D11

D10

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

Default

0x10

Line-In Volume

LVM

X

X

LLV4

LLV3

LLV2

LLV1

LLV0

RM1

X

X

RLV4

RLV3

RLV2

RLV1

RLV0

0x8808

If MSPLT is not set, the RM bit has no effect. All registers are not shown, and bits containing an X are assumed to be reserved. Refer to

for examples.

Table 22

Table 18.

Bit

Mnemonic

Function

RLV [4:0]

Line-In Volume Right

Allows setting the line-in right-channel attenuator in 32 volume levels. The LSB represents 1.5 dB, and

the range is +12 dB to −34.5 dB. The default value is 0 dB, mute enabled.

RM

Right-Channel Mute

Once enabled by the MSPLT bit in Register 0x76, this bit mutes the right channel separately from the

LM bit. Otherwise, this bit always reads 0 and has no effect when set to 1.

LLV [4:0]

Line-In Volume Left

Allows setting the line-in left-channel attenuator in 32 volume levels. The LSB represents 1.5 dB, and

the range is +12 dB to −34.5 dB. The default value is 0 dB, mute enabled.

LVM

Line-In Mute

When this bit is set to 1, both the left and right channels are muted, unless the MSPLT bit in

Register 0x76 is set to 1, in which case this mute bit affects only the left channel.