153 lines
2.9 KiB
C
153 lines
2.9 KiB
C
#include "bus.h"
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#include <stdlib.h>
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#include <stdio.h>
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#include <memory.h>
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#include "cpu.h"
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#include "ppu.h"
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#include "cartridge.h"
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struct Bus* createBus(SDL_Renderer* renderer)
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{
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struct Bus* bus = (struct Bus*)malloc(sizeof(struct Bus));
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if (bus == NULL)
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{
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fprintf(stderr, "Failed to create Bus object, aborting.");
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exit(1);
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}
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// 2KB of memory, equates to 2048 Bytes (0x800)
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bus->ram = (Byte*)malloc(0x800);
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if (bus->ram == NULL)
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{
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fprintf(stderr, "Failed to allocate memory for NES RAM, aborting.");
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exit(1);
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}
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memset(bus->ram, 0x00, 0x800);
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bus->io = (Byte*)malloc(0x18);
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if (bus->io == NULL)
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{
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fprintf(stderr, "Failed to allocate memory for NES I/O, aborting.");
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exit(1);
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}
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memset(bus->ram, 0x00, 0x18);
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// Create and insert cartridge
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bus->cartridge = createCartridge(bus, "roms/nestest.nes");
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// Create CPU and attach it
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bus->cpu = createCPU(bus);
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// Create PPU and attack it
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bus->screen = renderer;
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bus->ppu = createPPU(bus);
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bus->masterClockTimer = 0;
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return bus;
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}
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void destroyBus(struct Bus* bus)
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{
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destroyPPU(bus->ppu);
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destroyCPU(bus->cpu);
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destroyCartridge(bus->cartridge);
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free(bus->io);
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free(bus->ram);
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free(bus);
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}
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Byte readBus(struct Bus* bus, Word addr)
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{
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Byte val = 0;
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// Return from the appropriate device depending on the address
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if (addr <= 0x1FFF) // RAM (or one of the mirrored addresses)
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{
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val = bus->ram[addr & 0x7FF];
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}
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else if (0x2000 <= addr && addr < 0x4000)
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{
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val = ppuRead(bus->ppu, addr & 0x2007);
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}
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else if (0x4000 <= addr && addr <= 0x4017) // I/O space
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{
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switch (addr)
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{
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case 0x4016:
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val = pollInput(&bus->controller);
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break;
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}
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}
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else if (0x4020 <= addr && addr <= 0xFFFF) // Cartridge space
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{
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val = readCartridgeCPU(bus->cartridge, addr);
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}
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else
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{
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fprintf(stderr, "Access violation at $%x", addr);
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exit(1);
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}
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return val;
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}
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void writeBus(struct Bus* bus, Word addr, Byte val)
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{
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// writeCartridge to the appropriate memory or device
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if (addr <= 0x1FFF) // RAM (or one of the mirrored addresses)
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{
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bus->ram[addr & 0x7FF] = val;
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}
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else if (0x2000 <= addr && addr < 0x4000)
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{
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ppuWrite(bus->ppu, addr & 0x2007, val);
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}
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else if (0x4000 <= addr && addr <= 0x4017) // I/O space
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{
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switch (addr)
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{
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case 0x4016:
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bus->controller.strobe = (val & 0x1);
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if (val & 0x1)
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fillRegister(&bus->controller);
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break;
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}
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}
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else if (0x4020 <= addr && addr <= 0xFFFF) // Cartridge space
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{
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writeCartridgeCPU(bus->cartridge, addr, val);
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}
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else
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{
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fprintf(stderr, "Access violation at $%x", addr);
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exit(1);
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}
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}
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int tick(struct Bus* bus)
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{
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bus->masterClockTimer++;
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tickPPU(bus->ppu);
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if (bus->masterClockTimer == 3)
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{
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tickCPU(bus->cpu);
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bus->masterClockTimer = 0;
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}
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}
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int doInstruction(struct Bus* bus)
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{
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while(bus->cpu->remainingCycles > 0)
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tick(bus);
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tick(bus);
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}
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int doFrame(struct Bus* bus)
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{
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do tick(bus); while (bus->ppu->x != 0 || bus->ppu->y != 0);
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} |