Specifications

ESS Technology, Inc. SAM0023-122898 53
ES1869 DATA SHEET
PROGRAMMING THE ES1869
Resetting the Mixer Registers
The mixer registers are not affected by software reset. To
reset the registers to initial conditions, write any value to
mixer register 00h:
1. Write 00h to Audio_Base+4h
(select mixer register to 00h).
2. Write 00h to Audio_Base+5h
(write 00h to the selected mixer register).
Extended Access to SB Pro Mixer Volume Controls
The Sound Blaster Pro Mixer Volume controls are mostly
3 bits per channel. See the Sound Blaster Compatibility
register 04h in Table 23 for details. Bits 0 and 4 are always
high when read. The ES1869 offers an alternate way to
write each mixer register. Use the “extended access”
registers for volume control of 4 bits per channel. If the
Sound Blaster Pro compatible interface is used, bits 0 and
4 are cleared by a write and forced high on all reads. See
Table 18 for a list of Sound Blaster Pro registers and the
extended access counterparts.
For example, if you write 00h to Sound Blaster Pro register
04h, you will read back 11h because bits 0 and 4 are “stuck
high” on reads. Inside the register, these bits are “stuck
low,” so that writing 00h is the same as writing 11h.
A write or read to address 14h instead of 04h allows direct
access to all 8 bits of this mixer register.
Extended Access to Mic Mix Volume
If Sound Blaster Compatibility mode register address 0Ah
is used to control Mic Mix Volume, only bits 2 and 1 are
significant. Bit 0 is stuck high on reads and stuck low on
writes. Since this is a mono control, panning is not
supported.
For extended access, use register address 1Ah instead.
Register 1Ah offers 4 bits-per-channel for pan control of
the mono microphone input to the mixer.
Mic Mix Volume (1Ah, R/W)
Access to register 1Ah through address 0Ah is mapped as
follows:
Extended Access to ADC Source Select
In Sound Blaster Compatibility mode in the Sound Blaster
Pro mixer, there are three choices for recording source,
set by bits 2 and 1 of mixer register 0Ch. Note that bit 0 is
set to zero upon any write to 0Ch and set to one upon any
read from 0Ch:
For extended access, use register address 1Ch to select
recording from the mixer as follows:
Table 18 Sound Blaster Pro/Extended Access Registers
Register Function
Extended Access Register
for 4 bits/Channel
04h Voice volume 14h
22h Master volume 32h
26h FM volume 36h
28h CD (Aux) volume 38h
2Eh Line volume 3Eh
Mic mix volume left Mic mix volume right
7 6 5 4 3 2 1 0
Write to 0Ah D2=0, D1=0 Mic mix volume = 00h
D2=0, D1=1 Mic mix volume = 55h
D2=1, D1=0 Mic mix volume = AAh
D2=1, D1=1 Mic mix volume = FFh
Read from
0Ah
D2 = Mic Mix Volume register bit 3
D1 = Mic Mix Volume register bit 2
D0 = 1
others are undefined.
D2 D1 Source Selected
0 0 Microphone (default)
0 1 CD (Aux) input
1 0 Microphone
1 1 Line input
D2 D1 D0 Source Selected
x 0 x Microphone (default)
0 1 x CD (Aux) input
1 1 0 Line input
1 1 1 Mixer * (Bits 4:3 of Mixer register 7Ah deter-
mine if the mixer input source is the play-
back or record mixer).