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Merge pull request #2 from mtleblanc/emufixes

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Fix errors in 6502 emulation
This commit is contained in:
Nobuhiro Hatano 2022-04-09 09:30:49 +09:00 committed by GitHub
commit edb994f74d
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1 changed files with 7 additions and 7 deletions
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14
src/m6502.c
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@ -40,7 +40,7 @@
#define Z 0x02
#define C 0x01
static unsigned char accumulator, xRegister, yRegister, statusRegister = 0x24, stackPointer;
static unsigned char accumulator, xRegister, yRegister, statusRegister = I, stackPointer;
static int IRQ = 0, NMI = 0;
static unsigned short programCounter;
static unsigned char btmp;
@ -101,7 +101,7 @@ static void popProgramCounter(void)
static void handleIRQ(void)
{
pushProgramCounter();
memWrite((unsigned short)(0x100 + stackPointer), (unsigned char)(statusRegister & ~0x10));
memWrite((unsigned short)(0x100 + stackPointer), (unsigned char)((statusRegister & ~B) | M));
stackPointer--;
statusRegister |= I;
programCounter = memReadAbsolute(0xFFFE);
@ -111,7 +111,7 @@ static void handleIRQ(void)
static void handleNMI(void)
{
pushProgramCounter();
memWrite((unsigned short)(0x100 + stackPointer), (unsigned char)(statusRegister & ~0x10));
memWrite((unsigned short)(0x100 + stackPointer), (unsigned char)((statusRegister & ~B) | M));
stackPointer--;
statusRegister |= I;
NMI = 0;
@ -190,7 +190,7 @@ static void Ind(void)
static void IndZeroX(void)
{
ptr = xRegister + memRead(programCounter++);
ptr = (xRegister + memRead(programCounter++)) & 0xFF;
op = memRead(ptr);
op += memRead((unsigned short)((ptr + 1) & 0xFF)) << 8;
cycles += 3;
@ -319,7 +319,7 @@ static void ADC(void)
tmp = (Op1 & 0x0F) + (Op2 & 0x0F) + (statusRegister & C ? 1 : 0);
accumulator = tmp < 0x0A ? tmp : tmp + 6;
tmp = (Op1 & 0xF0) + (Op2 & 0xF0) + (tmp & 0xF0);
tmp = (Op1 & 0xF0) + (Op2 & 0xF0) + (accumulator & 0xF0);
if (tmp & 0x80)
statusRegister |= N;
@ -617,7 +617,7 @@ static void PHA(void)
static void PHP(void)
{
memWrite((unsigned short)(0x100 + stackPointer), statusRegister);
memWrite((unsigned short)(0x100 + stackPointer), statusRegister | B | M);
stackPointer--;
cycles++;
}
@ -641,7 +641,7 @@ static void BRK(void)
{
pushProgramCounter();
PHP();
statusRegister |= B;
statusRegister |= I;
programCounter = memReadAbsolute(0xFFFE);
cycles += 3;
}