
REV. 0
AD1888
–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]
D15 WRITE
READBACK Function
Right Channel Volume D[5:0]
WRITE
READBACK
MSPLT
*
D7
*
Function
0
0
00 0000
00 0000
0 dB Gain
x
00 0000
00 0000
0 dB Gain
0
0
00 1111
00 1111
–22.5 dB Gain
x
00 1111
00 1111
–22.5 dB Gain
0
0
01 1111
01 1111
–46.5 dB Gain
x
01 1111
01 1111
–46.5 dB Gain
0
0
1x xxxx
01 1111
–46.5 dB Gain
x
1x xxxx
01 1111
–46.5 dB Gain
0
1
xx xxxx
xx xxxx
– dB Gain, Muted
x
xx xxxx
xx xxxx
– dB Gain, Muted
1
0
1x xxxx
01 1111
–46.5 dB Gain
1
xx xxxx
xx xxxx
– dB Gain, only
Right Muted
1
1
xx xxxx
xx xxxx
– dB Gain, Left only Muted
0
xx xxxx
xx xxxx
–46.5 dB Gain
1
1
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 volume
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)
WRITE
D15
READBACK
Function
0
0
0
0 0000
0 1111
1 1111
x xxxx
0 0000
0 1111
1 1111
x xxxx
0 dB Gain
–22.5 dB Gain
–46.5 dB Gain
–
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
Volume
HPM
X LHV5 LHV4
LHV3
LHV2
LHV1
LHV0 HPRM
*
X RHV5 RHV4 RHV3 RHV2
RHV1 RHV0 8000h
*
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.