Specifications

48 SAM0025A-062397 ESS Technology, Inc.
ES1879 DATA SHEET
PROGRAMMING THE ES1879
PRELIMINARY
Mixing Modes Not Recommended
Avoid mixing Extended mode commands with
Compatibility mode commands. The Audio 1 DAC Enable/
Disable commands D1h and D3h are safe to use when
using Extended mode to process ADC or DAC. However,
other Compatibility mode commands can cause problems.
The Extended mode commands may be used to set up the
DMA or IRQ channels before entering Compatibility mode.
Data Formats
This section briefly describes the different audio data
formats used by the ES1879.
Compressed Data Formats
The ES1879 supports two types of compressed sound
DAC operations:
ESPCM
®
, which uses a variety of
proprietary compression techniques developed by ESS
Technology, and ADPCM, which is supported by many
other sound cards but is of a lower quality.
Both ADPCM and
ESPCM
®
are only transferred using DMA
transfer. The first block of a multiple-block transfer uses a
different command than subsequent blocks. The first byte
of the first block is called the reference byte.
Use Compatibility mode when transferring compressed
data.
Sound Blaster Pro-Compatible Data Formats
There are four formats available from combining the
following two options:

8-bit or 16-bit

Mono or stereo
The 8-bit samples are unsigned, ranging from 0h to 0FFh,
with the DC levels around 80h.
16-bit samples are unsigned, ranging from 0000h to
0FFFFh, with the DC levels around 8000h.
Stereo DMA Transfers in Compatibility Mode
Stereo DMA transfers are only available using DMA rather
than Direct mode commands.
To perform a stereo DMA transfer, first set bit 1 of mixer
register 0Eh high. Then set the timer divider to twice the
per-channel sample rate.
The maximum stereo transfer rate for 8-bit data is 22 kHz
per channel, so for this case, program the timer divider as
if it were for 44 kHz mono. The maximum stereo transfer
rate for 16-bit data is 11 kHz per channel. Stereo ADC
transfers for 16-bit data are not allowed in Compatibility
mode.
For 8-bit data, the ES1879 expects the first byte
transferred to be for the right channel, and subsequent
bytes to alternate left, right, etc.
Table 15 Comparison of Operation Modes
Compatibility Mode
(Sound Blaster Pro)
Extended Mode
Sound Blaster Pro-compatible Yes No
FIFO size 64 bytes (firmware managed) 256 bytes (hardware managed)
Mono 8-bit ADC, DAC Yes, to 44 kHz Yes, to 44 kHz
Mono 16-bit ADC, DAC Yes, to 22 kHz Yes, to 44 kHz
Stereo 8-bit DAC Yes, to 22 kHz Yes, to 44 kHz
Stereo 8-bit ADC Yes, to 22 kHz Yes, to 44 kHz
Stereo 16-bit DAC Yes, to 11 kHz Yes, to 44 kHz
Stereo 16-bit ADC No Yes, to 44 kHz
Signed/Unsigned Control No Yes
Automatic Gain Control during recording Firmware controlled, to 22 kHz, mono only No
Programmed I/O block transfer for ADC and DAC No Yes
FIFO status flags No Yes
Auto reload DMA Yes Yes
Time base for programmable timer 1 MHz or 1.5 MHz 800 kHz or 400 kHz
ADC and DAC jitter ± 2 microseconds None