Specifications

ESS Technology, Inc. SAM0025A-062397 75
ES1879 DATA SHEET
REGISTERS
PRELIMINARY
I
2
S Record Volume (6Fh, R/W)
This register controls the record volume for the I
2
S input.
Set low by hardware reset but not by mixer reset.
Audio 2 Mixer Registers
This section describes registers related to the second
audio channel. These registers are accessed via I/O
addresses Audio_Base+4h and Audio_Base+5h.
Audio 2 Sample Rate Generator (70h, R/W)
This register should be programmed for the sample rate
for all DAC operations in extended mode.
The sample rate is determined by the two’s complement
divider in bits 6:0.
Sample_Rate = Clock_Source / (256 - Sample_Rate_Divider)
This register is reset to zero by hardware reset.
Bits Definitions:
Audio 1 and Audio 2 Mode (71h, R/W)
This register controls a variety of modes for the first and
second audio channels.
This register is reset to zero by hardware reset.
Bits Definitions:
I
2
S record volume left I
2
S record volume right
76543210
Clock
source
Sample rate divider
76543210
Bits Name Description
7 Clock
source
1 = 768 kHz (used to generate 48 kHz, 32 kHz,
16 kHz, 8 kHz, etc.).
0 = 793.8 kHz (used to generate 44.1 kHz,
22.05 kHz, etc.).
6:0 Sample
rate
divider
Signed sample rate divider of master clock.
For example:
value
sample rate
A0h 8000
F0h 48000
6Eh 44100
0
I
2
S
enable
Controller
register A1h
mode select
Audio 2
oversam-
pling
enable
Audio 2
SCF
bypass
enable
Audio 1
SCF
bypass
enable
Asynchro-
nous
mode
enable
FM
mix
enable
76 5 4 3 2 1 0
Bits Name Description
7 – Reserved. Always write 0.
6
I
2
S
enable
1 = Enable I
2
S source input.
0 = Disable I
2
S source input.
5 Control-
ler regis-
ter A1h
mode
select
1 = Enable controller register A1h to behave
just as mixer register 70h. This gives more
accurate sample rates that are divisors of 48
kHz..
0 = Controller register A1h behaves as
described under that register’s description.
4 Audio 2
oversam-
pling
enable
1 = enable 4x oversampling mode for the
Audio 2 DAC. This mode bypasses the switch
capacitor filter.
0 = Disable oversampling for the Audio 2 DAC.
3 Audio 2
SCF
bypass
enable
1 = Enable bypass of the switch capacitor filter
for the Audio 2 DAC. This filter is bypassed
automatically when bit 4 of this register is set
high.
0 = Disable bypass of the switch capacitor filter
for the Audio 2 DAC.
2 Audio 1
SCF
bypass
enable
1 = Enable bypass of the switch capacitor filter
for the Audio 1 CODEC.
0 = Disable bypass of the switch capacitor filter
for the Audio 1 CODEC.
1Asyn-
chronous
mode
enable
1 = The sample rate for Audio 2 may be asyn-
chronous to Audio 1.
0 = the Audio 2 sample rate is slaved to the
sample rate for Audio 1.
0 FM mix
enable
1 = Audio 2 is slaved to the FM synthesizer
sample rate and digitally mixed with the FM
synthesizer output.
0 = Audio 2 is not slaved to the FM synthe-
sizer.