mirror of https://github.com/bsnes-emu/bsnes.git
30 lines
747 B
C++
30 lines
747 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(r.dmaLength == 0 || r.dmaSource.byte(2) == 1) {
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r.dmaEnable = false;
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return;
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}
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wait(5);
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while(r.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(r.dmaSource.byte(2) != 1) {
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data |= read(r.dmaSource + 0) << 0;
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data |= read(r.dmaSource + 1) << 8;
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write(r.dmaTarget + 0, data >> 0);
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write(r.dmaTarget + 1, data >> 8);
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}
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if(r.dmaMode == 0) {
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r.dmaSource += 2;
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r.dmaTarget += 2;
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} else {
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r.dmaSource -= 2;
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r.dmaTarget -= 2;
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}
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r.dmaLength -= 2;
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};
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r.dmaEnable = false;
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}
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