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#define FALSE 0
#define TRUE 1
enum Addressing {
eImmediate,
eAccumulator,
eAbsolute,
eAbsoluteIndexedX,
eAbsoluteIndexedY,
eZeroPage,
eZeroPageIndexedX,
eZeroPageIndexedY,
eIndexedIndirect,
eIndirectIndexed,
eImplied,
eIndirectAbsolute,
eRelative
};
typedef int Addressing;
/*
* Any addressing method which is single line commented out without definition
* implies that handling should be hard-coded in the switch case of the
* instruction from which it came.
*/
struct AddData{
int cycles;
int length;
byte value;
};
AddData fAddress(Addressing addr, short x) {
AddData ret;
switch(addr){
case eImmediate: ret.value = x; break;
case eAccumulator: ret.value = acc; break;
case eAbsolute: ret.value = Memory[x]; break;
case eAbsoluteIndexedX: ret.value = Memory[(x + X)]; break;
case eAbsoluteIndexedY: ret.value = Memory[(x + Y)]; break;
case eZeroPage: ret.value = Memory[(x & 0x00FF)]; break;
case eZeroPageIndexedX: ret.value = Memory[((x = X) & 0x00FF)]; break;
case eZeroPageIndexedY: ret.value = Memory[((x = Y) & 0x00FF)]; break;
case eIndexedIndirect: ret.value = Memory[((x + X) << 8) + ((x + X) + 1)]; break;
case eIndirectIndexed: ret.value = ((Memory[x] + Memory[(x+1 << 8)]) + Y); break;
//case eImplied: No reference
//case eIndirectAbsolute: Only used in the JMP instruction
//case eRelative: Only used in branch instructions
}
switch(addr){
case eAbsolute: case eAbsoluteIndexedX: case eAbsoluteIndexedY:
ret.length = 3; break;
case eAccumulator:
ret.length = 1; break;
default:
ret.length = 2; break;
}
// FOR TIME, FIND THE PARTICULAR VALUE SET FOR THE FIRST TYPE,
// APPLY RELATIVE MOVEMENT
// THEN LET THE FUNCTION WHICH CALLED fAddress HANDLE A NON-TYPICAL VALUE.
}
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