mirror of https://github.com/bsnes-emu/bsnes.git
30 lines
737 B
C++
30 lines
737 B
C++
auto CPU::dmaTransfer() -> void {
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//length of 0 or SRAM source address cause immediate termination
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if(s.dmaLength == 0 || s.dmaSource.b2 == 1) {
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s.dmaEnable = false;
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return;
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}
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wait(5);
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while(s.dmaLength) {
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wait(2);
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uint16 data = 0;
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//once DMA is started; SRAM reads still incur time penalty, but do not transfer
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if(s.dmaSource.b2 != 1) {
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data |= read(s.dmaSource + 0) << 0;
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data |= read(s.dmaSource + 1) << 8;
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write(s.dmaTarget + 0, data >> 0);
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write(s.dmaTarget + 1, data >> 8);
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}
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if(s.dmaMode == 0) {
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s.dmaSource += 2;
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s.dmaTarget += 2;
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} else {
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s.dmaSource -= 2;
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s.dmaTarget -= 2;
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}
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s.dmaLength -= 2;
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};
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s.dmaEnable = false;
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}
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