Specifications

84 SAM0025A-062397 ESS Technology, Inc.
ES1879 DATA SHEET
AUDIO MICROCONTROLLER COMMAND SUMMARY
PRELIMINARY
AUDIO MICROCONTROLLER COMMAND SUMMARY
Table 28 Command Summary
Command
Data Byte(s)
Write/Read
Function
10h 1 write Direct write 8-bit DAC. Data is 8-bit unsigned format.
11h 2 writes Direct write 16-bit DAC. Data is 16-bit unsigned format, first low byte then high byte.
14h 2 writes Start Normal mode DMA for 8-bit DAC transfer. Data is transfer count-1, least byte first. Stereo DAC
transfer if Stereo flag is set in Mixer register 0Eh. Maximum sample rate is 44 kHz mono, 22 kHz ste-
reo.
15h 2 writes Start Normal mode DMA for 16-bit DAC transfer. Data is transfer count-1, least byte first. Stereo
DAC transfer if Stereo flag is set in Mixer register 0Eh. Maximum sample rate is 22 kHz mono,
11 kHz stereo.
1Ch Start Auto-Initialize mode DMA for 8-bit DAC transfer. Block size must be previously set by com-
mand 48h. Stereo DAC transfer if Stereo flag is set in Mixer register 0Eh. Maximum sample rate is
44 kHz mono, 22 kHz stereo.
1Dh Start Auto-Initialize mode DMA for 16-bit DAC transfer. Block size must be previously set by com-
mand 48h. Stereo DAC transfer if Stereo flag is set in Mixer register 0Eh. Maximum sample rate is
22 kHz mono, 11 kHz stereo.
20h 1 read Direct mode 8-bit ADC. Data is 8-bit unsigned. Firmware-controlled input volume for AGC.
21h 2 read Direct mode 16-bit ADC, returns least byte first. Data is 16-bit unsigned format. Input volume con-
trolled via command DDh.
24h 2 writes Start Normal mode DMA for 8-bit ADC transfer. Data is transfer count-1, least byte first. Firmware-
controlled input volume for AGC. Maximum sample rate is 22 kHz: use command 99h for higher
rates up to 44 kHz.
25h 2 writes Start Normal mode DMA for 16-bit ADC transfer. Data is transfer count-1, least byte first. Input vol-
ume controlled via command DDh. Maximum sample rate is 22 kHz.
2Ch Start Auto-Initialize mode DMA for 8-bit ADC transfer. Block size must be previously set by com-
mand 48h. Firmware-controlled input volume for AGC. Maximum sample rate is 22 kHz: use com-
mand 98h for higher rates up to 44 kHz.
2Dh Start Auto-Initialize mode DMA for 16-bit ADC transfer. Block size must be previously set by com-
mand 48h. Input volume is controlled via command DDh. Maximum sample rate is 22 kHz.
30h/31h MIDI input mode. Detects MIDI serial input data and transfers to Data register, setting Data-Available
flag in register Audio_Base+Eh. Command 31h will also generate an interrupt request for each byte
received.
Exit MIDI input mode by executing a write to port Audio_Base+Ch. The data written is ignored. A
software reset will also exit this mode.
34h/35h MIDI UART mode. Acts like commands 30h and 31h, except that any data written to Audio_Base+Ch
will be transmitted as MIDI serial output data. The only way to exit this mode is a software reset.
38h 1 write MIDI output. Transmit one byte.
40h 1 write Set time constant, X, for timer used for DMA mode DAC/ADC transfers: rate = 1 MHz / (256-X). X
must be less than or equal to 233. For stereo DAC, program sample rate for twice the per-channel
rate.
41h 1 write Alternate set time constant, X: rate = 1.5 MHz / (256-X). This command provides more accurate tim-
ing for certain rates such as 22,050. X must be less than or equal to 222. For stereo DAC, program
sample rate for twice the per-channel rate.
42h 1 write Set filter clock independently of timer rate. (Note that the filter clock is automatically set by com-
mands 40h/41h.) Filter clock rate = 7.16E6 / (256-X).
The relationship between the low-pass filter -3 dB point and the filter clock rate is approximately
1:82.
48h 2 writes Set block size to -1 for High-Speed mode and Auto-Initialize mode transfer, least byte first.