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Handle zero page wraparound in ($xx,X) 

* fixes line #1100: CFF4  C9 5D     CMP
This commit is contained in:
Rob McMullen 2017-12-18 11:48:56 -08:00
parent 44dfdfaca5
commit 986a9f33b6
1 changed files with 9 additions and 3 deletions
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6502.c
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@ -528,7 +528,13 @@ uint8_t * get_IND()
uint8_t * get_XIND()
{
uint16_t ptr;
memcpy(&ptr, get_ZPX(), sizeof(ptr));
ptr = ((* get_IMM()) + X) & 0xFF;
if (ptr == 0xff) { // check for wraparound in zero page
ptr = memory[ptr] + (memory[ptr & 0xff00] << 8);
}
else {
memcpy(&ptr, &memory[ptr], sizeof(ptr));
}
return &memory[ptr];
}
@ -588,7 +594,7 @@ void init_tables() // this is only done at runtime to improve code readability.
lengths[ZPX] = 2;
lengths[ZPY] = 2;
lengths[JMP_IND_BUG] = 3;
/* Addressing Modes */
get_ptr[ACC] = get_ACC;
@ -604,7 +610,7 @@ void init_tables() // this is only done at runtime to improve code readability.
get_ptr[ZPX] = get_ZPX;
get_ptr[ZPY] = get_ZPY;
get_ptr[JMP_IND_BUG] = get_JMP_IND_BUG;
/* Instructions */
instructions[0x00] = (Instruction) {"BRK impl", inst_BRK, IMPL, 7,};