mirror of https://github.com/bsnes-emu/bsnes.git
86 lines
3.0 KiB
C++
86 lines
3.0 KiB
C++
auto CPU::_idle() -> void {
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prefetchStep(1);
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}
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auto CPU::_read(uint mode, uint32 addr) -> uint32 {
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uint wait = this->wait(mode, addr);
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uint word = pipeline.fetch.instruction;
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if(addr >= 0x1000'0000) {
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prefetchStep(wait);
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} else if(addr & 0x0800'0000) {
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if(mode & Prefetch && regs.wait.control.prefetch) {
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prefetchSync(addr);
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word = prefetchRead();
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if(mode & Word) word |= prefetchRead() << 16;
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} else {
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if(!active.dma) prefetchWait();
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step(wait - 1);
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word = cartridge.read(mode, addr);
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step(1);
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}
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} else {
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prefetchStep(wait - 1);
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if(addr < 0x0200'0000) word = bios.read(mode, addr);
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else if(addr < 0x0300'0000) word = readEWRAM(mode, addr);
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else if(addr < 0x0400'0000) word = readIWRAM(mode, addr);
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else if(addr >= 0x0700'0000) word = ppu.readOAM(mode, addr);
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else if(addr >= 0x0600'0000) word = ppu.readVRAM(mode, addr);
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else if(addr >= 0x0500'0000) word = ppu.readPRAM(mode, addr);
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else if((addr & 0xffff'fc00) == 0x0400'0000) word = bus.io[addr & 0x3ff]->readIO(mode, addr);
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else if((addr & 0xff00'ffff) == 0x0400'0800) word = ((IO*)this)->readIO(mode, 0x0400'0800 | (addr & 3));
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prefetchStep(1);
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}
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return word;
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}
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auto CPU::_write(uint mode, uint32 addr, uint32 word) -> void {
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uint wait = this->wait(mode, addr);
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if(addr >= 0x1000'0000) {
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prefetchStep(wait);
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} else if(addr & 0x0800'0000) {
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if(!active.dma) prefetchWait();
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step(wait);
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cartridge.write(mode, addr, word);
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} else {
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prefetchStep(wait);
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if(addr < 0x0200'0000);
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else if(addr < 0x0300'0000) writeEWRAM(mode, addr, word);
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else if(addr < 0x0400'0000) writeIWRAM(mode, addr, word);
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else if(addr >= 0x0700'0000) ppu.writeOAM(mode, addr, word);
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else if(addr >= 0x0600'0000) ppu.writeVRAM(mode, addr, word);
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else if(addr >= 0x0500'0000) ppu.writePRAM(mode, addr, word);
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else if((addr & 0xffff'fc00) == 0x0400'0000) bus.io[addr & 0x3ff]->writeIO(mode, addr, word);
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else if((addr & 0xff00'ffff) == 0x0400'0800) ((IO*)this)->writeIO(mode, 0x0400'0800 | (addr & 3), word);
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}
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}
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auto CPU::wait(uint mode, uint32 addr) -> uint {
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if(addr >= 0x1000'0000) return 1; //unmapped
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if(addr < 0x0200'0000) return 1;
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if(addr < 0x0300'0000) return (16 - regs.memory.control.ewramwait) * (mode & Word ? 2 : 1);
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if(addr < 0x0500'0000) return 1;
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if(addr < 0x0700'0000) return mode & Word ? 2 : 1;
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if(addr < 0x0800'0000) return 1;
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static uint timings[] = {5, 4, 3, 9};
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uint n = timings[regs.wait.control.nwait[addr >> 25 & 3]];
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uint s = regs.wait.control.swait[addr >> 25 & 3];
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switch(addr & 0x0e00'0000) {
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case 0x0800'0000: s = s ? 2 : 3; break;
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case 0x0a00'0000: s = s ? 2 : 5; break;
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case 0x0c00'0000: s = s ? 2 : 9; break;
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case 0x0e00'0000: s = n; break;
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}
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bool sequential = (mode & Sequential);
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if((addr & 0x1fffe) == 0) sequential = false; //N cycle on 16-bit ROM crossing 128KB page boundary (RAM S==N)
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uint clocks = sequential ? s : n;
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if(mode & Word) clocks += s; //16-bit bus requires two transfers for words
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return clocks;
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}
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