REV. 0

AD1980

–11–

Table I. Volume Settings for Master and Headphone

Control Bits

Reg. 76h

Master Volume (02h) and Headphone Volume (04h)

Left Channel Volume D[13:8]

Right Channel Volume D[5:0]

MSPLT

*

D15 WRITE

READBACK Function

D7

*

WRITE

READBACK

Function

00

00 0000

00 0000

0 dB Gain

x

00 0000

00 0000

0 dB Gain

00

00 1111

00 1111

–22.5 dB Gain

x

00 1111

00 1111

–22.5 dB Gain

00

01 1111

01 1111

–46.5 dB Gain

x

01 1111

01 1111

–46.5 dB Gain

00

1x xxxx

01 1111

–46.5 dB Gain

x

1x xxxx

01 1111

–46.5 dB Gain

01

xx xxxx

xx xxxx

–

dB Gain, Muted

x

xx xxxx

xx xxxx

–

dB Gain, Muted

10

1x xxxx

01 1111

–46.5 dB Gain

1

xx xxxx

xx xxxx

–

dB Gain, only

Right Muted

11

xx xxxx

xx xxxx

–

dB Gain, Left only Muted

0

xx xxxx

xx xxxx

–46.5 dB Gain

11

xx xxxx

xx xxxx

–

dB Gain, Left Muted

1

xx xxxx

xx xxxx

–

dB Gain, Right

Muted

*For AC ’97 compatibility, Bit D7 is available only by setting the MSPLT bit, Register 76h. The MSPLT bit enables separate mute bits for the left and right

channels. If MSPLT is not set, Bit D7 has no effect.

x in the above table is “don’t care.”

Mono Volume Register (Index 06h)

Reg

No.

Name

D15

D14

D13

D12

D11

D10

D9

D8

D7

D6

D5

*

D4

D3

D2

D1

D0

Default

06h

Mono Volume

MVM

X

X

X

X

X

X

X

X

X

MV5

MV4

MV3

MV2

MV1

MV0

8000h

*Refer to Table II for examples. 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 vol-

ume bits are automatically set to “1” by the codec logic. On readback, all lower five bits will read “1s” whenever this bit is set to “1.” All registers not shown and bits

containing an X are assumed to be reserved.

MV[5:0]

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 II. Volume Settings for Mono

Control Bits D[4:0] for Mono (06h)

D15

WRITE

READBACK

Function

00 0000

0 0000

0 dB Gain

00 1111

0 1111

–22.5 dB Gain

01 1111

1 1111

–46.5 dB Gain

1x xxxx

x xxxx

– dB Gain, Muted

x in the above table is a wild card and has no effect on the value.

Headphones Volume Register (Index 04h)

Reg

No.

Name

D15

D14

D13

D12

D11

D10

D9

D8

D7

D6 D5

D4

D3

D2

D1

D0

Default

04h

Headphones

HPM

X

LHV5 LHV4 LHV3 LHV2 LHV1 LHV0 HPRM

* X

RHV5 RHV4 RHV3 RHV2

RHV1 RHV0 8000h

Volume

*For AC ’97 compatibility, Bit D7 is available only by setting the MSPLT bit, Register 76h. The MSPLT bit enables separate mute bits for the left and right

channels. If MSPLT is not set, Bit D7 has no effect.