AD1985 datasheet(40/48 Pages) AD

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AD1985

Rev. A | Page 40 of 48

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 0x72).

The upper bit allows forcing the down-mix function:

DMIX[1] = 0: No down-mix unless activated by the jack senses 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 L/R channels.

(Default.)

DMIX[0] = 1: Selects 6-to-2 down-mix. The surround L/R channels are summed into the mixer L/R channels. The center and

LFE are summed equally 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, and 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 surround

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 (approximately 30 kΩ

impedance) mode so that the assigned output audio jacks 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 (approximately 30 kΩ impedance) 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 left and right channels in 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 their 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. Changing this bit allows the surround, center, and LFE volume control registers and output

attenuators to operate in a more functional mode than what’s defined by the AC ’97 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 0x18

(PCM volume). The output pin attenuators for the surround are controlled by Register 0x38 and the output pin attenuators

for the center and LFE are controlled by Register 0x36.

In ADI compatibility mode, the surround DAC gain/attenuators are controlled by Register 0x38 and the center/LFE DAC

gain/attenuators are controlled by Register 0x36. The output pin attenuators for the surround, center, and LFE are

controlled by Register 0x02 (master volume).

0: AC ’97 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.

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