Specifications

Digitized Sound I/O Programming 3-21

8-bit Stereo High-speed Single-cycle Transfer

The following are the steps needed to perform 8-bit stereo 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. Set the hardware to stereo mode.

a. For stereo input:

outp(wSBCBaseAddx+0xC, 0xA8)

b. For stereo output:

i. Set stereo mode.

outp(wSBCBaseAddx+0x4, 0xE)

bTmp = inp(wSBCBaseAddx+0x5)

outp(wSBCBaseAddx+0x5, (bTmp | 0x2))

ii. Program the DMA controller for one byte single-cycle output.

iii. Program the DSP to output one silent byte (value 0x80).

outp(wSBCBaseAddx+0xC, 0x14)

outp(wSBCBaseAddx+0xC, 0)

iv Upon receiving a DSP interrupt, acknowledge the DSP then exit

the ISR.

5. Program the DMA controller for 8-bit single-cycle DMA mode transfer.

6. Set the DSP transfer Time Constant.

outp(wSBCBaseAddx+0xC, 0x40)

outp(wSBCBaseAddx+0xC, bTimeConstant)

7. Preserve the current input and output filter status, then turn it off.

a. For stereo input:

outp(wSBCBaseAddx+0x4, 0xC)

bInputFilter = inp(wSBCBaseAddx+0x5)

outp(wSBCBaseAddx+0x5, (bInputFilter | 0x20))

b. For stereo output:

outp(wSBCBaseAddx+0x4, 0xE)

bOutputFilter = inp(wSBCBaseAddx+0x5)

outp(wSBCBaseAddx+0x5, (bOutputFilter | 0x20))