REV. 0

AD1981A

–10–

Headphones Volume Register (Index 04h)

1

Reg Num Name

D15 D14 D13

D12

D11

D10

D9

D8

D7 D6 D5

D4

D3

D2

D1

D0

Default

04h

Headphones Volume HPM

X

X

LHV4 LHV3 LHV2 LHV1 LHV0 RM

2

X

X RHV4 RHV3 RHV2 RHV1 RHV0 8000h

NOTES

with 31 steps of 1.5 dB each. Because AC ‘97 defines 6-bit volume registers, to maintain compatibility whenever the D5 or D13 Bits are set to “1, ” their respective

lower five volume bits are automatically set to “1” by the CODEC logic. On readback, all lower 5 bits will read ones when ever these bits are set to “1.”

channels. If MSPLT is not set, RM bit has no effect.

RHV [4:0]

Right Headphone 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.

RM

Right Channel Mute: Once enabled by the MSPLT Bit in Register 76h, this bit mutes the right channel separately

from the HPM Bit. Otherwise, this bit will always read “0” and will have no effect when set to “1.”

LHV [4:0]

Left Headphone 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.

HPM

Headphones Volume Mute: When this bit is set to “1,” both L/R channels are muted, unless the MSPLT Bit in

Register 76h is set to “1,” in which case, this mute bit will only affect the left channel.

xHV5…xHV0

Function

HPM

WRITE

READBACK

Function

0

00 0000

00 0000

0 dB Gain

0

00 1111

00 1111

–22.5 dB Gain

0

01 1111

01 1111

–46.5 dB Gain

0

1x xxxx

01 1111

–46.5 dB Gain

1

xx xxxx

xx xxxx

–

∞ dB Gain

Mono Volume (Index 06h)

*

Reg Num Name

D15

D14 D13 D12 D11 D10 D9 D8 D7 D6 D5

D4

D3

D2

D1

D0

Default

06h

Mono Volume MVM

XXXXX

XXXXX

MV4 MV3 MV2 MV1 MV0

8000h

*This register controls the headphone volume controls for both stereo channels and mute bit. Each volume subregister contains 5 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 or D13 Bits are set to “1, ” their respective

lower five volume bits are automatically set to “1” by the CODEC logic. On readback, all lower 5 bits will read ones when ever these bits are set to “1.”

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.

xMV5…xMV0

MVM

WRITE

READBACK

Function

0

00 0000

00 0000

0 dB Gain

0

00 1111

00 1111

–22.5 dB Gain

0

01 1111

01 1111

–46.5 dB Gain

0

1x xxxx

01 1111

–46.5 dB Gain

1

xx xxxx

xx xxxx

–

∞ dB Gain

Phone Volume (Index 0Ch)

Reg Num Name

D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5

D4

D3

D2

D1

D0

Default

0Ch

Phone Volume

PHM

XXXXX

XXXXX PHV4 PHV3 PHV2 PHV1 PHV0

8008h