AD1981B Analog Devices, AD1981B Datasheet - Page 11

• Manufacturer Part Number: AD1981B
• Description: AD1981B AC'97 SoundMAX® Codec
• Manufacturer: Analog Devices

Reg. 76h
MSPLT*
0
0
0
0
0
1
1
1
*For AC ’97 compatibility, Bit D7 (RM) is available only by setting the MSPLT bit, Register 76h. The MSPLT bit enables separate mute bits for the left and right
REV. A
*For AC ’97 compatibility, Bit D7 (RM) is available only by setting the MSPLT bit, Register 76h. The MSPLT bit enables separate mute bits for the left and right
Refer to Table I for examples. This register controls the headphone volume controls for both stereo channels and mute bit. Each
volume subregister 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 or D13 bits are set to “1,” their respective lower five volume bits are automati-
cally set to “1” by the codec logic. On readback, all lower five bits will read “1s” whenever these bits are set to “1.”
RHV [4:0]
RM
LHV [4:0]
HPM
Reg
No. Name
04h Headphone HPM X
channels. If MSPLT is not set, RM bit has no effect.
X in the above table is a wild card and has no effect on the value.
channels. If MSPLT is not set, RM bit has no effect. All registers not shown and bits containing an X are assumed to be reserved.
Volume
D15 WRITE
0
0
0
0
1
0
1
1
D15
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.
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.”
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.
Headphones Volume Mute. When this bit is set to “1,” both the left and right channels are muted, unless the
MSPLT bit in Register 76h is set to “1,” in which case this mute bit will affect only the left channel.
00 0000
00 1111
01 1111
1x xxxx
xx xxxx
1x xxxx
xx xxxx
xx xxxx
D14
Left Channel Volume D[13:8]
D13
X
READBACK Function
00 0000
00 1111
01 1111
01 1111
xx xxxx
01 1111
xx xxxx
xx xxxx
D12
LHV
4
Table I. Volume Settings for Master and Headphone
Master Volume (02h) and Headphone Volume (04h)
D11
LHV
3
0 dB Gain
–22.5 dB Gain
–46.5 dB Gain
–46.5 dB Gain
– dB Gain, Muted
–46.5 dB Gain
– dB Gain, Left Only Muted
– dB Gain, Left Muted
Headphones Volume Register (Index 04h)
D10
LHV
2
D9
LHV
1
D8
LHV
0
Control Bits
–11–
D7
RM*
X
D6
D7* WRITE READBACK
x
x
x
x
x
1
0
1
D5
X
Right Channel Volume D[5:0]
00 0000 00 0000
00 1111 00 1111
01 1111 01 1111
1x xxxx
xx xxxx
xx xxxx
xx xxxx
xx xxxx
D4
RHV
4
D3
RHV
3
01 1111
xx xxxx
xx xxxx
xx xxxx
xx xxxx
D2
RHV
2
RHV
1
D1
Function
0 dB Gain
–22.5 dB Gain
–46.5 dB Gain
–46.5 dB Gain
– dB Gain, Muted
– dB Gain, Right
Only Muted
–46.5 dB Gain
– dB Gain, Right
Muted
AD1981B
D0
RHV
0
Default
8000h