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start fixing bugs with memory access

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So this is why tests should be written while writing the program
and instructions instead of all at once later. If this were all to be
rewritten (which it probably will), I should add tests for each opcode
instead of waiting until the end for ROM loading support.
This commit is contained in:
Vineet K 2024-06-17 15:11:45 +05:30
parent 77d37dd455
commit 6a5b0b728e
1 changed files with 10 additions and 10 deletions
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20
cpu.c
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@ -81,10 +81,8 @@ peek(uint16_t addr)
static uint16_t
peek16(uint16_t addr)
{
MEMORY_MIRROR(addr);
/* bytes are stored in little-endian (low then high) */
return (uint16_t)memory[addr] | ((uint16_t)memory[addr + 1] << 8);
return peek(addr) | (peek(addr + 1) << 8);
}
static void
@ -108,7 +106,7 @@ memwrite16(uint16_t addr, uint16_t word)
static uint8_t
opcode_arg(enum addressing_mode mode)
{
uint8_t arg, val;
uint16_t arg, val;
if (mode != AM_ABS && mode != AM_ABS_X && mode != AM_ABS_Y)
arg = peek(regs.pc++);
@ -149,14 +147,15 @@ opcode_arg(enum addressing_mode mode)
abort();
}
printf("arg: $%04X $%04X\n", arg, val);
return val;
}
static uint16_t
opcode_mem(enum addressing_mode mode)
{
uint8_t arg;
uint16_t val;
uint16_t arg, val;
if (mode != AM_ABS && mode != AM_ABS_X && mode != AM_ABS_Y)
arg = peek(regs.pc++);
@ -173,6 +172,7 @@ opcode_mem(enum addressing_mode mode)
case AM_ZP_Y:
val = (arg + regs.y) % 256;
break;
case AM_IMM:
case AM_ABS:
val = arg;
break;
@ -1059,7 +1059,7 @@ interpret(void)
cycles += 2;
break;
case 0x4c:
jmp(opcode_arg(AM_ABS));
jmp(opcode_mem(AM_ABS));
cycles += 3;
break;
case 0x6c:
@ -1111,7 +1111,7 @@ interpret(void)
cycles += 5;
break;
case 0xa2:
ldx(opcode_arg(AM_IMM));
ldx(opcode_mem(AM_IMM));
cycles += 2;
break;
case 0xa6:
@ -1467,8 +1467,8 @@ main(int argc, char *argv[])
return 1;
}
memwrite16(0xFFFC, 0x8000);
regs.pc = 0x8000;
memwrite16(0xFFFC, 0xC000);
regs.pc = 0xC000;
printf("status: %i%i%i%i%i%i%i%i\n", regs.status.carry,
regs.status.zero, regs.status.interrupt_disable,