mirror of https://github.com/bsnes-emu/bsnes.git
74 lines
1.8 KiB
C++
74 lines
1.8 KiB
C++
auto CPU::dma_run() -> void {
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active.dma = true;
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while(true) {
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bool transferred = false;
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for(auto n : range(4)) {
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auto& dma = regs.dma[n];
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if(dma.pending) {
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dma_exec(dma);
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if(dma.control.irq) regs.irq.flag.dma[n] = 1;
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if(dma.control.drq && n == 3) regs.irq.flag.cartridge = 1;
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transferred = true;
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break;
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}
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}
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if(!transferred) break;
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}
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active.dma = false;
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}
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auto CPU::dma_exec(Registers::DMA& dma) -> void {
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unsigned seek = dma.control.size ? 4 : 2;
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unsigned mode = dma.control.size ? Word : Half;
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mode |= dma.run.length == dma.length ? Nonsequential : Sequential;
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if(mode & Nonsequential) {
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if((dma.source & 0x0800'0000) && (dma.target & 0x0800'0000)) {
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//ROM -> ROM transfer
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} else {
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idle();
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idle();
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}
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}
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uint32 word = bus_read(mode, dma.run.source);
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bus_write(mode, dma.run.target, word);
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switch(dma.control.sourcemode) {
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case 0: dma.run.source += seek; break;
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case 1: dma.run.source -= seek; break;
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}
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switch(dma.control.targetmode) {
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case 0: dma.run.target += seek; break;
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case 1: dma.run.target -= seek; break;
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case 3: dma.run.target += seek; break;
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}
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if(--dma.run.length == 0) {
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dma.pending = false;
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if(dma.control.targetmode == 3) dma.run.target = dma.target;
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if(dma.control.repeat == 1) dma.run.length = dma.length;
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if(dma.control.repeat == 0) dma.control.enable = false;
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}
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}
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auto CPU::dma_vblank() -> void {
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for(auto& dma : regs.dma) {
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if(dma.control.enable && dma.control.timingmode == 1) dma.pending = true;
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}
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}
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auto CPU::dma_hblank() -> void {
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for(auto& dma : regs.dma) {
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if(dma.control.enable && dma.control.timingmode == 2) dma.pending = true;
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}
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}
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auto CPU::dma_hdma() -> void {
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auto& dma = regs.dma[3];
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if(dma.control.enable && dma.control.timingmode == 3) dma.pending = true;
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}
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