Datasheet

OBSOLETE

LM4550

SNAS032F –SEPTEMBER 2001–REVISED APRIL 2013

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Table 16. SLOT 4, INPUT FRAME

Bits Description Comment

19:2 PCM Record Right Channel data 18-bit PCM audio sample from right ADC

1:0 Reserved Stuffed with "0"s by LM4550

SDATA_IN: Slots 5 to 12 – Reserved

Slots 5 – 12 of the AC Link Input Frame are not used for data by the LM4550 and are always stuffed with zeros.

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 LM4550 will return a value of 0D50h. This value can be

interpreted in accordance with the AC '97 specification to indicate that National 3D Sound is implemented, 18-bit

data is supported for both the ADCs and DACs, and that headphone output is supported.

MASTER VOLUME REGISTER (02h)

This output register allows the output level from either channel 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.

Mute Mx4:Mx0 Function

0 0 0000 0dB attenuation

0 1 1111 46.5dB attenuation

1 X XXXX *mute

Default: 8000h

HEADPHONE VOLUME REGISTER (04h)

This output register allows the level from both channels of HP_OUT to be muted or individually 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 plus one

mute bit. The mute bit (D15) acts on both channels. Operation of this register and HP_OUT matches that of the

Master Volume register and the LINE_OUT output.

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).

Mute MM4:MM0 Function

0 0 0000 0dB attenuation

0 1 1111 46.5dB attenuation

1 X XXXX *mute

Default: 8000h

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.

Product Folder Links: LM4550