AD1981B

Rev. C | Page 15 of 32

MONO VOLUME REGISTER

Index 0x06

This register controls the mono output volume and mute bit. The volume register contains five bits, generating 32 volume levels with

31 steps of 1.5 dB each. Because AC ’97 defines 6-bit volume registers, to maintain compatibility, whenever the D5 bit is set to 1, their

respective lower five volume bits are automatically set to 1 by the codec logic. On readback, all lower five bits read 1s whenever this bit is

set to 1. Refer to Table 14 for examples.

Reg No.

Name

D15

D14

D13

D12

D11

D10

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

Default

0x06

Mono Volume

MVM

X

X

X

X

X

X

X

X

X

X

MV4

MV3

MV2

MV1

MV0

0x8000

All registers are not shown, and bits containing an X are assumed to be reserved.

Table 13.

Bit

Mnemonic

Function

MV [4:0]

Mono Volume Control

The least significant bit represents 1.5 dB. This register controls the output from 0 dB to a maximum

attenuation of 46.5 dB.

MVM

Mono Volume Mute

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

Table 14. Volume Settings for Mono

Control Bits D [4:0] for Mono (0x06)

D15

Write

Readback

Function

0

0000

0 0000

0 dB Gain

0

0 1111

0 1111

−22.5 dB Gain

0

1 1111

1 1111

−46.5 dB Gain

1

X XXXX

X XXXX

−∞ dB Gain, Muted

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

PHONE VOLUME REGISTER

Index 0x0C

Reg No.

Name

D15

D14

D13

D12

D11

D10

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

Default

0x0C

Phone Volume

PHM

X

X

X

X

X

X

X

X

X

X

PHV4

PHV3

PHV2

PHV1

PHV0

0x8008

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

Table 15.

Bit

Mnemonic

Function

PHV [4:0]

Phone Volume

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.

PHM

Phone Mute

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

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