AD1981B Analog Devices, AD1981B Datasheet - Page 16

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

AD1981B
RIM[3:0]
RM
LIM[3:0]
IM
Reg. 76h
MSPLT* D15 WRITE READBACK
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
x is a wild card and has no effect on the value.
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
MIX
Reg
No. Name
20h
channels. If MSPLT is not set, RM bit has no effect.
General-Purpose
0
0
1
0
1
1
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.”
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.
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.
Mono Output Select. Selects mono output audio source.
0 = Mixer mono output (reset default).
1 = MIC1 channel.
1111
0000
xxxx
1111
xxxx
xxxx
Left Channel Input Mixer D[11:8]
D15
X
1111
0000
xxxx
1111
xxxx
xxxx
D14
X
D13
X
D12
X
Table VI. Settings for Record Gain Register
Function
22.5 dB Gain
0 dB Gain
– dB Gain, Muted
22.5 dB Gain
– dB Gain,
Left Only Muted
– dB Gain,
Left Muted
General-Purpose Register (Index 20h)
D11
X
X
D10
Record Gain (1Ch)
Control Bits
D9
MIX
–16–
D8
MS
D7*
x
x
x
1
0
1
D7
LPBK
WRITE READBACK Function
1111
0000
xxxx
xxxx
1111
xxxx
Right Channel Input Mixer D[3:0]
D6
X
D5
X
1111
0000
xxxx
xxxx
1111
xxxx
D4
X
D3
X
22.5 dB Gain
0 dB Gain
– dB Gain, Muted
– dB Gain,
Right Only Muted
22.5 dB Gain
– dB Gain, Right Muted
D2
X
D1
X
D0
X
REV. A
Default
0000h