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fix indirect JMP bug where the high byte does not increment out of page

Browse Source 
https://old.reddit.com/r/EmuDev/comments/15plfes/having_an_issue_with_nestest_on_my_6502_emulator/jvyck7k/

With this, it seems that all official opcodes run as nestest expects.
Now, it's the unofficial opcodes that need to be implemented.
This commit is contained in:
Vineet K 2024-06-30 15:14:38 -04:00
parent 718f89c9c5
commit 4525490beb
1 changed files with 4 additions and 3 deletions
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7
cpu.c
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@ -196,7 +196,7 @@ opcode_mem(enum addressing_mode mode)
val = arg + regs.y; val = arg + regs.y;
break; break;
case AM_IND: case AM_IND:
val = peek16(arg); val = peek(arg) | (peek(((arg + 1) & 0xFF) | (arg & 0xFF00)) << 8);
break; break;
case AM_IND_X: case AM_IND_X:
val = peek((arg + regs.x) % 256) + peek((arg + regs.x + 1) % 256) * 256; val = peek((arg + regs.x) % 256) + peek((arg + regs.x + 1) % 256) * 256;
@ -1308,9 +1308,10 @@ interpret(void)
case 0x6c: case 0x6c:
mode = AM_IND; mode = AM_IND;
mem = peek16(regs.pc); mem = peek16(regs.pc);
deref = peek(mem); deref = peek16(mem);
arg = opcode_mem(mode); arg = opcode_mem(mode);
jmp(deref); deref = arg;
jmp(arg);
cycles += 6; cycles += 6;
printf("JMP"); printf("JMP");
break; break;