Register Descriptions

Reset Register (00h)

Writing any value to this register causes a register reset

which changes all of the registers back to their default val-

ues. If this register is read, the LM4546 will return a value of

0D50h indicating that National 3D Sound is implemented

and 18bit data is supported by both the ADCs and DACs.

Master Volume Registers (02h, 06h)

These two registers allow the output levels from LINE_OUT,

and MONO_OUT to be attenuated or muted. There are

6-bits of volume control, plus one mute bit. It is a 5-bit vol-

ume range, where each step is nominally 1.5dB and each

output can be individually muted by either setting the most

significant bit (Mx5), and/or the mute bit (D15) to

″1.″

Mute

Mx5:Mx0

Function

0

00 0000

0dB attenuation

0

01 1111

46.5dB attenuation

0

1X XXXX

46.5dB attenuation

1

XX XXXX

mute

Default: 8000h

PC Beep Register (0Ah)

This register controls the level of the PC_BEEP input. The

PC_BEEP can be both attenuated and muted via register

0Ah. Step size is nominally 3dB. The signal present after the

attenuation and mute block is summed into both the left and

right channels.

Mute

PV3:0

Function

0

0000

0dB attenuation

0

1111

45dB attenuation

1

XXXX

mute

Default: 0000h

Mixer Input Volume Registers (Index 0Ch - 12h, 18h)

These registers set the input volume levels including mute.

Each volume control is 5 bit which provides from a range of

+12dB gain to 34.5dB attenuation in 1.5dB steps. For stereo

ports, the left and right levels can be independently set. Mut-

ing a given port is accomplished by setting the MSB to 1.

Setting the MSB to 1 for stereo ports mutes both the left and

right channel. Register 0Eh has an additional 20dB boost for

a microphone level input. This is enabled by setting bit 6 of

register 0Eh to 1.

Mute

Gx4:Gx0

Function

0

00000

+12dB gain

0

01000

0dB gain

0

11111

34.5dB attenuation

1

XXXXX

mute

Default: 8008h (mono regs.), 8808h (stereo regs.)

Record Select Register (1Ah)

This register independently controls the source for the right

and left channel which will be recorded by the stereo ADC.

The default value is 0000h which corresponds to Mic in.

SL2:SL0

Left Record Source

0

Mic

1

CDIn(L)

2

not used

3

not used

4

Line In (L)

5

Stereo Mix (L)

6

Mono Mix (L)

7

Phone

SR2:SR0

Right Record Source

0

Mic

1

CDIn(R)

2

not used

3

not used

4

Line In (R)

5

Stereo Mix (R)

6

Mono Mix (R)

7

Phone

Record (Input) Gain Register (1Ch)

This registers controls the Record (Input) Gain level for the

stereo input selected via the Record Select Control Register

(1Ah). The gain can be programmed from 0dB to +22.5dB in

1.5dB steps. The level for the left and right channel can be

individually controlled. The input can also be muted by set-

ting the MSB to 1.

Mute

Gx3:Gx0

Function

0

1111

22.5dB gain

0

0000

0dB gain

1

XXXX

mute

Default: 8000h

General Purpose Register (20h)

This register controls many miscellaneous functions imple-

mented on the LM4546. The miscellaneous functions include

POP which allows the PCM to bypass the National 3D

Sound circuitry, 3D which enables or disables the National

3D Sound circuitry, MIX which selects the MONO_OUT

source, MS which selects the microphone mux source, and

LPBK which connects the output of the stereo ADC to the in-

put of the stereo DAC. LPBK provides a digital loopthru path

when enabled.

BIT

Function

POP

PCM out path and mute,0=pre 3D,1=

post 3D

3D

National 3D Sound on / off1=on

MIX

Mono output select0=Mix,1=Mic

MS

Mic select 0 = Mic1 1 = Mic2

LPBK

ADC/DAC loopback

Powerdown Control / Status Register (26h)

This read/write register is used to monitor subsystem readi-

ness and also to program the LM4546 powerdown states.

The lower half of this register is read only with a

″1″, indicat-

ing the subsection is ready. Writing to the lower 8 bits will

have no effect.

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