mirror of https://github.com/bsnes-emu/bsnes.git
145 lines
3.1 KiB
C++
145 lines
3.1 KiB
C++
auto PPU::readCIRAM(uint11 addr) -> uint8 {
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return ciram[addr];
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}
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auto PPU::writeCIRAM(uint11 addr, uint8 data) -> void {
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ciram[addr] = data;
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}
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auto PPU::readCGRAM(uint5 addr) -> uint8 {
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if((addr & 0x13) == 0x10) addr &= ~0x10;
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uint8 data = cgram[addr];
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if(io.grayscale) data &= 0x30;
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return data;
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}
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auto PPU::writeCGRAM(uint5 addr, uint8 data) -> void {
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if((addr & 0x13) == 0x10) addr &= ~0x10;
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cgram[addr] = data;
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}
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auto PPU::readIO(uint16 addr) -> uint8 {
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uint8 result = 0x00;
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switch(addr.bits(0,2)) {
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//PPUSTATUS
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case 2:
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result |= io.mdr.bits(0,4);
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result |= io.spriteOverflow << 5;
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result |= io.spriteZeroHit << 6;
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result |= io.nmiFlag << 7;
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io.v.latch = 0;
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io.nmiHold = 0;
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cpu.nmiLine(io.nmiFlag = 0);
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break;
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//OAMDATA
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case 4:
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result = oam[io.oamAddress];
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break;
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//PPUDATA
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case 7:
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if(enable() && (io.ly <= 240 || io.ly == 261)) return 0x00;
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addr = (uint14)io.v.address;
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if(addr <= 0x1fff) {
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result = io.busData;
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io.busData = cartridge.readCHR(addr);
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} else if(addr <= 0x3eff) {
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result = io.busData;
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io.busData = cartridge.readCHR(addr);
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} else if(addr <= 0x3fff) {
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result = readCGRAM(addr);
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io.busData = cartridge.readCHR(addr);
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}
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io.v.address += io.vramIncrement;
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break;
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}
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return result;
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}
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auto PPU::writeIO(uint16 addr, uint8 data) -> void {
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io.mdr = data;
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switch(addr.bits(0,2)) {
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//PPUCTRL
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case 0:
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io.t.nametable = data.bits(0,1);
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io.vramIncrement = data.bit (2) ? 32 : 1;
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io.spriteAddress = data.bit (3) ? 0x1000 : 0x0000;
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io.bgAddress = data.bit (4) ? 0x1000 : 0x0000;
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io.spriteHeight = data.bit (5) ? 16 : 8;
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io.masterSelect = data.bit (6);
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io.nmiEnable = data.bit (7);
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cpu.nmiLine(io.nmiEnable && io.nmiHold && io.nmiFlag);
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break;
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//PPUMASK
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case 1:
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io.grayscale = data.bit (0);
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io.bgEdgeEnable = data.bit (1);
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io.spriteEdgeEnable = data.bit (2);
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io.bgEnable = data.bit (3);
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io.spriteEnable = data.bit (4);
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io.emphasis = data.bits(5,7);
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break;
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//PPUSTATUS
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case 2:
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break;
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//OAMADDR
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case 3:
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io.oamAddress = data;
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break;
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//OAMDATA
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case 4:
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if(io.oamAddress.bits(0,1) == 2) data.bits(2,4) = 0; //clear non-existent bits (always read back as 0)
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oam[io.oamAddress++] = data;
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break;
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//PPUSCROLL
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case 5:
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if(io.v.latch++ == 0) {
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io.v.fineX = data.bits(0,2);
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io.t.tileX = data.bits(3,7);
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} else {
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io.t.fineY = data.bits(0,2);
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io.t.tileY = data.bits(3,7);
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}
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break;
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//PPUADDR
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case 6:
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if(io.v.latch++ == 0) {
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io.t.addressHi = data.bits(0,5);
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} else {
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io.t.addressLo = data.bits(0,7);
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io.v.address = io.t.address;
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}
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break;
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//PPUDATA
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case 7:
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if(enable() && (io.ly <= 240 || io.ly == 261)) return;
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addr = (uint14)io.v.address;
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if(addr <= 0x1fff) {
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cartridge.writeCHR(addr, data);
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} else if(addr <= 0x3eff) {
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cartridge.writeCHR(addr, data);
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} else if(addr <= 0x3fff) {
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writeCGRAM(addr, data);
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}
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io.v.address += io.vramIncrement;
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break;
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}
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}
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