Specifications

56 SAM0023-122898 ESS Technology, Inc.
ES1869 DATA SHEET
REGISTERS
REGISTERS
Register Types
Types of Register Access
There are two types of audio registers in the ES1869:
• Mixer registers.
These registers are accessed through I/O ports Audio_Base+4h and Audio_Base+5h. Audio_Base+4h is written
with the register address. Then the register can be read written through Audio_Base+5h. These registers control
many functions other than the mixer.
• Controller registers.
These registers are used to control Extended mode DMA playback and record through the first audio channel.
Controller registers are accessed through an extension to the Sound Blaster common interface. This interface
uses I/O ports Audio_Base+Ah, Audio_Base+Ch, and Audio_Base+Eh to transfer read data, write data/
commands, and status respectively.
Mixer Registers
There are two types of mixer registers. Sound Blaster Pro Compatible mixer registers are fully compatible with the Sound
Blaster Pro. ESS mixer registers are specific to ESS Technology, Inc. ES1869 AudioDrive
®
chips, although many registers
are shared throughout the AudioDrive
®
family of chips.
Sound Blaster Pro Compatible Mixer Registers
This section provides a summary of Sound Blaster Pro compatible mixer registers in the ES1869 and some comments
on the characteristics of these registers.
* Sound Blaster Filter Control bits F2, F1, and F0 have no equivalent function in the ES1869 and are ignored.
Filter Control Bits
The Sound Blaster Pro mixer has three bits that control
input and output filters. They are labeled F0, F1, and F2 in
Table 23 and Table 24. They have no equivalent function
in the ES1869 and their values are ignored.
Mixer Stereo Control Bit
Bit 1 of register 0Eh is the Mixer Stereo Control bit. It is
normally zero. Set this bit high to enable Sound Blaster
Pro compatible stereo DAC functions. In this case,
program the DAC sample rate to be twice the sample rate
of each channel. For example, for 22 kHz stereo, program
the “sample rate” to be 44 kHz using command 40h.
This bit enables stereo only for DMA transfer to the DAC
in Compatibility mode. It should not be used in Extended
mode.
Clear this bit after completing the stereo DMA transfer,
because this bit is unaffected by software reset (only mixer
reset).
See also “Stereo DMA Transfers in Compatibility Mode”
on page44.
Table 23 Sound Blaster Compatibility Register Summary
Reg D7 D6 D5 D4 D3 D2 D1 D0 Description
00h Write: reset mixer Mixer reset
04h DAC play volume left X DAC play volume right X DAC playback volume
0Ah X X X X X Mic mix volume X Mic mix volume
0Ch X X F1 * X F0 * ADC source X See note for F0, F1.
0Eh X X F2 * X X X Stereo X See note for F2.
22h Master volume left X Master volume right X Master volume
26h FM volume left X FM volume right X Music DAC volume
28h AuxA (CD) volume left X AuxA (CD) volume right X AuxA (CD) volume
2Eh Line volume left X Line volume right X Line volume