lm4546a National Semiconductor Corporation, lm4546a Datasheet - Page 21

• Manufacturer Part Number: lm4546a
• Description: Ac ?97 Rev 2 Multi-channel Audio Codec With Sample Rate Conversion And National 3d Sound
• Manufacturer: National Semiconductor Corporation

Register Descriptions
Default settings are indicated by *.
RESET REGISTER (00h)
Writing any value to this register causes a Register Reset
which changes all registers back to their default values. If a
read is performed on this register, the LM4546A will return a
value of 0D40h. This value can be interpreted in accordance
with the AC ’97 specification to indicate that National 3D
Sound is implemented and 18-bit data is supported for both
the ADCs and DACs.
MASTER VOLUME REGISTER (02h)
This output register allows the output level from either chan-
nel of the stereo LINE_OUT to be muted or attenuated over
the range 0 dB – 46.5 dB in nominal 1.5 dB steps. There are
5 bits of volume control for each channel and both stereo
channels can be individually attenuated. The mute bit (D15)
acts simultaneously on both stereo channels of LINE_OUT.
MONO VOLUME REGISTER (06h)
This output register allows the level from MONO_OUT to be
muted or attenuated over the range 0 dB – 46.5 dB in
nominal 1.5 dB steps. There are 5 bits of volume control and
one mute bit (D15).
PC BEEP VOLUME REGISTER (0Ah)
This input register adjusts the level of the mono PC_BEEP
input to the stereo mixer MIX2 where it is summed equally
into both channels of the Stereo Mix signal. PC_BEEP can
be both muted and attenuated over a range of 0 dB to 45 dB
in nominal 3 dB steps. Note that the default setting for the
PC_Beep Volume register is 0 dB attenuation rather than
mute.
MIXER INPUT VOLUME REGISTERS (Index 0Ch - 18h)
These input registers adjust the volume levels into the stereo
mixers MIX1 and MIX2. Each channel may be adjusted over
a range of +12dB gain to 34.5dB attenuation in 1.5dB steps.
For stereo ports, volumes of the left and right channels can
be independently adjusted. Muting a given port is accom-
plished by setting the MSB to 1. Setting the MSB to 1 for
stereo ports mutes both the left and right channel. The Mic
Default: 8000h
Default: 8000h
Default: 0000h
Mute
Mute
Mute
0
0
1
0
0
1
0
0
1
MM4:MM0
Mx4:Mx0
PV3:PV0
X XXXX
X XXXX
0 0000
0 0000
1 1111
1 1111
XXXX
0000
1111
0dB attenuation
46.5dB attenuation
*mute
0dB attenuation
46.5dB attenuation
*mute
*0dB attenuation
45dB attenuation
mute
Function
Function
Function
21
Volume register (0Eh) controls an additional 20dB boost for
the selected microphone input by setting the 20dB bit (D6).
RECORD SELECT REGISTER (1Ah)
This register independently controls the sources for the right
and left channels of the stereo ADC. The default value of
0000h corresponds to selecting the (mono) Mic input for both
channels.
RECORD GAIN REGISTER (1Ch)
This register controls the input levels for both channels of the
stereo ADC. The inputs come from the Record Select Mux
and are selected via the Record Select Control register, 1Ah.
The gain of each channel can be individually programmed
from 0dB to +22.5dB in 1.5dB steps. Both channels can also
be muted by setting the MSB to 1.
Default:
Default: 0000h
Default: 8000h
SR2:SR0
SL2:SL0
Mute
Mute
0
0
0
1
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
0
0
1
8008h (mono registers)
8808h (stereo registers)
Record Gain Register (1Ch)
Gx4:Gx0
Gx3:Gx0
X XXXX
0 0000
0 1000
1 1111
XXXX
0000
1111
Source for Right Channel ADC
Source for Left Channel ADC
*Mic input
CD input (L)
VIDEO input (L)
AUX input (L)
LINE_IN input (L)
Stereo Mix (L)
Mono Mix
PHONE input
*Mic input
CD input (R)
VIDEO input (R)
AUX input (R)
LINE_IN input (R)
Stereo Mix (R)
Mono Mix
PHONE input
+12dB gain
0dB gain
34.5dB attenuation
*mute
22.5dB gain
0dB gain
*mute
Function
Function
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