Creative SB0350 Hardware Programming Guide - Page 50

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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 singlecycle DMA mode transfer: 1. 2. 3. Set up the DSP interrupt service routine. Enable the interrupt used. Turn on the DAC speaker for digitized output. Otherwise, turn it off. to turn off the DAC speaker outp(wSBCBaseAddx+0xC, 0xD3) to turn on the DAC speaker outp(wSBCBaseAddx+0xC, 0xD1) Set the hardware to stereo mode. a. For stereo input: outp(wSBCBaseAddx+0xC, 0xA8) 4. 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) outp(wSBCBaseAddx+0xC, 0) iv Upon receiving a DSP interrupt, acknowledge the DSP then exit the ISR. 5. 6. Program the DMA controller for 8-bit single-cycle DMA mode transfer. 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))

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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)
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))