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AD1980

DMIX[1:0]

Down Mix Mode Select. Provides analog down-mixing of the center, LFE, and/or surround channels into the

mixer channels. This allows the full content of 5.1 or quad media to be played through stereo headphones or

speakers.

Note that the Jack Sense pins can also be set up to control (gate) this function depending on the JS0DMX and

JS1DMX Bits (see Register 72h).

The upper bit allows forcing the down-mix function:

DMIX[1] = 0, no down-mix unless activated by the Jack Sense and JSxDMX bits (default).

DMIX[1] = 1, forces down-mix function.

The lower bit selects the down-mix type:

DMIX[0] = 0, selects 6-to-4 down-mix. The center and LFE channels are summed equally into the mixer left and

right channels (default).

DMIX[0] = 1, selects 6-to-2 down-mix. The surround left and right channels are summed into the mixer left and

right channels.

Default for DMIX[1:0] is “00.”

HPSEL

Headphone Amplifier Input Select. This bit allows the headphone power amps to be driven from the surround

DACs or from the mixer outputs. There are two reasons for this: one is to allow 2-channel media to use the

higher power headphone amplifiers available on the SURR/HP_OUT outputs; the other is to allow spreading of

2-channel media to the surround outputs.

Together with the LOSEL bit (see above), this bit also provides for analog swapping of the mixer (front) and sur-

round outputs.

0 = SURR_out/HP_out outputs are driven by the surround DACs (reset default).

1 = SURR_out/HP_out outputs are driven by the mixer outputs.

CLDIS

Center and LFE Disable. Disables the center and LFE output pins, placing them into High-Z mode so that the

assigned output audio jack(s) can be shared for MIC inputs or other functions.

0 = Center and LFE output pins have normal audio drive capability (reset default).

1 = Center and LFE output pins are placed into High-Z mode.

LODIS

Line_out Disable. Disables the Line_out pins (L/R), placing them into High-Z mode so that the assigned output

audio jack can be shared for Line Input function.

0 = Line_out pins have normal audio drive capability (reset default).

1 = Line_out pins are placed into High-Z mode.

MSPLT

Mute Split. Allows separate mute control bits for master, HP, Line_in, CD, PCM OUT, and record volume/gain

control registers.

0 = Both left and right channel mutes are controlled by Bit D15 in the respective registers (reset default).

1 = Bit D15 affects only the left channel mute and Bit D7 affects only the right channel mute.

AC97NC

AC ’97 No Compatibility Mode. This bit allows the surround, center, and LFE volume control registers and

output attenuators to operate in a more functional mode than defined by the AC97 2.2 spec. This is called ADI

compatibility mode.

In AC ’97 compatibility mode, the DAC Gain/Attenuators for the surround, center, and LFE are controlled by

Register 18h (PCM volume). The output pin attenuators for the surround are controlled by Register 38h, and the

output pin attenuators for the center and LFE are controlled by Register 36h.

In ADI compatibility mode, the Surround DAC Gain/Attenuators are controlled by Register 38h, and the Center/

LFE DAC are controlled by Register 36h.

The output pin attenuators for Center/LFE are controlled by Register 02h (Master Volume), and the output pin

attenuators for Surround are controlled by Register 04h.

0 = AC97 compatibility mode (reset default).

1 = ADI compatibility mode.

DACZ

DAC Zero-Fill. Determines DAC data fill under starved condition.

0 = DAC data is repeated when DACs are starved for data (reset default).

1 = DAC data is zero-filled when DACs are starved for data.