All of the legacy sound blaster mixer register except MX80, MX81 and MX82 are implemented virtually using the opl3 emulation

RAM (512 bytes). Please refer to section 2.3 to get detailed description of the virtual implementation method.

The implemented MX80, MX81 are all read/write registers. Contents of MX80 and MX81 must be consistent with header 1 inter-

rupt line configuration register. MX80 and MX81 can be accessed through AudioBase based port. MX82 is a part of the Audio in-

terrupt status register.

4.2.1.18 Implementation Note For Legacy Sound Blaster Mixer

4.2.1.18.1

To ease our design and maintain the game compatibility on mixer volume set, writing to the legacy sound blaster mixer

register will set a dirty flag, and this flag will inform the software which one of the AC97 mixer should be updated and

then update it using AudioBase based programming port.

When any one of the SBPRO mixer registers (mixer index from 00h–2Fh) has been updated, a SBPRO volume update dirty flag

will be set at Audio Status Register ASR0.

When any one of the SB16 mixer registers (mixer index from 30h–4Fh) has been updated, a SB16 volume update dirty flag will

be set at Audio Status Register ASR0.

Any time when legacy sound blaster mixer is mixer-reset, a mixer soft-reset dirty flag will be set at Audio Status Register ASR0.

All the SB16 / SBPRO mixer register (index from 02h to 4fh) are implemented using part of the opl3 emulation RAM(512bytes).

Any of the unused RAM cell (mixer index above 48h) can be used as the scratch registers for specific purpose and that’s user

defined.

The AC97 internal mixer registers are accessed via another AudioBase based port. (See 4. AC 97)

4.2.1.19 SBPRO Mixer Register

MX00 Mixer Reset

Write only

Any write to this port will reset MX00-MX4f to default value.

SB ESP_Reset() does not affect any of the mixer register.

When this port is written, a SB mixer soft-reset dirty flag will

be set in ASR0.

MX02 Master Volume

Default

808h

Write

Bit 7..4

reserved

Bit 3..0

16 level master volume for left and right channel

Read

Bit 7..4

master volume for left channel

Bit 3..0

master volume for right channel

MX04 Digital Audio Volume

Default 88h

Write

Bit 7..4 16 level left digital audio volume

Bit 3..0 16 level right digital audio volume

Read

Bit 7..4 left digital audio volume

Bit 3..0 right digital audio volume

MX06 Music Volume

Default 88h

Write

Bit 7..4 reserved

Bit 3..0 16 level music volume for left and right channel

Read

Bit 7..4 left music volume

Bit 3..0 right music volume

MX08 CD-Audio Volume

Default 00h

Write

Bit 7..4 reserved

Bit 3..0 16 level CD-Audio volume for left and right channel

Read

Bit 7..4 left CD-Audio volume

Bit 3..0 right CD-Audio volume

MX0A Microphone Volume

Default 00h

Write

Bit 7..3 reserved

Bit 2..0 8 level microphone volume

Read

Bit 7..3 reserved

Bit 2..0 microphone volume

MX0C Digital Audio Input Control

Default 00h

Dummy read/write register

Bit 7,6 reserved

Bit 5

input filter enable

Bit 4

reserved

Bit 3

input filter high/low

Bit 2,1 input source

Bit 0

reserved

Input filter enable and input filter high/low are dummy read/

write bits for SB PRO compatibility.

Input filter enable: 0 - input low-pass filter on,1-off

Input filter high/low: 0 - low filter (3.2 kHz low pass), 1 - high

filter (8.8 kHz low pass)

Input source

Bit 2 Bit 1

0

0

Microphone

0

1

CD-Audio

1

0

Microphone

1

1

External Line-In

MX0E Digital Audio Output Control

Default 00h

Bit 7,6

reserved

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