Specifications

3-22 Digitized Sound I/O Programming
8. Set the DSP block transfer size.
outp(wSBCBaseAddx+0xC, 0x48)
outp(wSBCBaseAddx+0xC, wBlkSize.LowByte)
outp(wSBCBaseAddx+0xC, wBlkSize.HighByte)
wBlkSize
is one less than the actual transfer size.
9. 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
Upon receiving an interrupt from the DSP, the following steps should be done in the
interrupt service routine:
1. Program the DMA controller for subsequent block.
2. Set the DSP block size and program the DSP for the next block.
At the end of data transfer:
1. Restore the filter status.
a. For stereo input:
outp(wSBCBaseAddx+0x4, 0xC)
outp(wSBCBaseAddx+0x5, bInputFilter)
b. For stereo output:
outp(wSBCBaseAddx+0x4, 0xE)
outp(wSBCBaseAddx+0x5, bOutputFilter)
2. Set the hardware to mono mode.
a. For stereo input:
outp(wSBCBaseAddx+0xC, 0xA0)
b. For stereo output:
outp(wSBCBaseAddx+0x4, 0xE)
bTmp = inp(wSBCBaseAddx+0x5)
outp(wSBCBaseAddx+0x5, (bTmp & 0xFD))
3. Turn off the DAC speaker.
outp(wSBCBaseAddx+0xC, 0xD3)
4. Disable the interrupt used.
5. Restore the original interrupt service routine.
During high-speed DMA mode data I/O, the DSP will not accept any commands.
Hence, to stop data transfer before the end of a block, send the reset DSP command.