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added interrupts

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This commit is contained in:
Lauchmelder 2021-10-24 16:52:15 +02:00
parent 56c9dfbe6e
commit 034645154d
3 changed files with 60 additions and 1 deletions
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49
NES Emulator/cpu.c
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@ -37,6 +37,9 @@ struct CPU* createCPU(struct Bus* parent)
cpu->remainingCycles = 7;
cpu->totalCycles = 0;
cpu->irq = 0;
cpu->nmi = 0;
cpu->bus = parent;
return cpu;
}
@ -54,6 +57,40 @@ int tickCPU(struct CPU* cpu)
cpu->remainingCycles--;
cpu->totalCycles += 1;
if (cpu->remainingCycles == 1)
{
// Handle interrupts
if (cpu->nmi)
{
Push(cpu->bus, cpu->pc.hi);
Push(cpu->bus, cpu->pc.lo);
Push(cpu->bus, cpu->status.raw & 0b11101111);
cpu->nmi = 0;
cpu->pc.lo = readBus(cpu->bus, 0xFFFA);
cpu->pc.hi = readBus(cpu->bus, 0xFFFB);
return 0;
}
if (!cpu->status.id)
{
if (cpu->irq)
{
Push(cpu->bus, cpu->pc.hi);
Push(cpu->bus, cpu->pc.lo);
Push(cpu->bus, cpu->status.raw & 0b11101111);
cpu->status.id = 1;
cpu->pc.lo = readBus(cpu->bus, 0xFFFE);
cpu->pc.hi = readBus(cpu->bus, 0xFFFF);
cpu->irq = 0;
}
}
}
if (cpu->remainingCycles == 0)
{
fetch(cpu);
@ -189,7 +226,7 @@ void fetch(struct CPU* cpu)
void execute(struct CPU* cpu)
{
LOG_BUS(cpu->bus);
// LOG_BUS(cpu->bus);
switch (cpu->currentOpcode->op)
{
@ -795,3 +832,13 @@ void execute(struct CPU* cpu)
break;
}
}
void IRQ(struct CPU* cpu)
{
cpu->irq = 1;
}
void NMI(struct CPU* cpu)
{
cpu->nmi = 1;
}