AD1981B
Record Gain Register (Index 1Ch)
Reg
No. Name
D15 D14 D13 D12 D11
D10
D9
D8
D7
D6
D5 D4 D3
D2
D1
D0
Default
1Ch Record Gain IM
X
X
X
LIM3 LIM2
LIM1 LIM0 RM*
X
X
X
RIM3 RIM2 RIM1 RIM0 8000h
*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
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. Refer to Table VI for examples.
RIM[3:0]
RM
Right Input Mixer Gain Control. Each LSB represents 1.5 dB, 0000 = 0 dB, and the gain range is 0 dB to 22.5 dB.
Right Channel Mute. Once enabled by the MSPLT bit in Register 76h, this bit mutes the right channel separately
from the IM bit. Otherwise, this bit will always read 0 and will have no affect when set to 1.
LIM[3:0]
IM
Left Input Mixer Gain Control. Each LSB represents 1.5 dB, 0000 = 0 dB, and the gain range is 0 dB to 22.5 dB.
Input 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.
Table VI. Settings for Record Gain Register
Control Bits
Record Gain (1Ch)
Reg. 76h
Left Channel Input Mixer D[11:8]
MSPLT* D15 WRITE READBACK Function
Right Channel Input Mixer D[3:0]
D7* WRITE READBACK Function
0
0
0
1
0
0
1
0
1111
0000
xxxx
1111
1111
0000
xxxx
1111
22.5 dB Gain
0 dB Gain
x
x
x
1
1111
0000
xxxx
xxxx
1111
0000
xxxx
xxxx
22.5 dB Gain
0 dB Gain
–ꢁ dB Gain, Muted
22.5 dB Gain
–ꢁ dB Gain, Muted
–ꢁ dB Gain,
Right Only Muted
1
1
1
1
xxxx
xxxx
xxxx
xxxx
–ꢁ dB Gain,
Left Only Muted
0
1
1111
xxxx
1111
xxxx
22.5 dB Gain
–ꢁ dB Gain,
–ꢁ dB Gain, Right Muted
Left Muted
*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
channels. If MSPLT is not set, RM bit has no effect.
x is a wild card and has no effect on the value.
General-Purpose Register (Index 20h)
Reg
No. Name
D15
D14 D13 D12 D11 D10 D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
Default
20h General-Purpose
X
X
X
X
X
X
MIX MS
LPBK
X
X
X
X
X
X
X
0000h
This register should be read before writing to generate a mask for only the bit(s) that need to be changed. All registers not shown and bits containing an X are assumed
to be reserved.
LPBK
MS
Loopback Control. ADC/DAC Digital Loopback Mode.
0 = No Loopback (Default).
1 = Loopback PCM Digital Data from ADC Output to DAC.
MIC Select. Selects mono MIC input.
0 = Select MIC1.
1 = Select MIC2.
See 2CMIC bit in Register 76h to enable stereo microphone recording.
MIX
Mono Output Select. Selects mono output audio source.
0 = Mixer mono output (reset default).
1 = MIC1 channel.
REV. B
–16–
ADI [ ADI ]
