Specifications

Digitized Sound I/O Programming 3-17
8-bit Mono High-Speed Single-cycle Transfer
The following are the steps needed to perform 8-bit mono PCM high-speed single-
cycle DMA mode transfer:
1. Set up the DSP interrupt service routine.
2. Enable the interrupt used.
3. Turn on the DAC speaker for digitized output. Otherwise, turn it off.
outp(wSBCBaseAddx+0xC, 0xD3)
to turn off the DAC speaker
outp(wSBCBaseAddx+0xC, 0xD1)
to turn on the DAC speaker
4. Program the DMA controller for 8-bit single-cycle DMA mode transfer.
5. Set the DSP transfer Time Constant.
outp(wSBCBaseAddx+0xC, 0x40)
outp(wSBCBaseAddx+0xC, bTimeConstant)
6. Set the DSP transfer block size.
outp(wSBCBaseAddx+0xC, 0x48)
outp(wSBCBaseAddx+0xC, wBlkSize.LowByte)
outp(wSBCBaseAddx+0xC, wBlkSize.HighByte)
wBlkSize
is one byte less than the actual data transfer size.
7. Send an I/O command to start high-speed single-cycle DMA mode
transfer.
outp(wSBCBaseAddx+0xC, bCommand)
bCommand
is one of the following:
bCommand Description
99h
8-bit PCM high-speed input
91h
8-bit PCM high-speed output
When the DSP sends an interrupt, the following steps should be done in the interrupt
service routine:
1. Program the DMA controller for the next block.
2. Set the DSP block size and program the DSP for the next block.