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// addressing.h
// Contains definitions relevant to addressing, as well as fAddress() which returns time, length, value, and address for an instruction function call.
// Would like to refactor the code into something better, such as switch-case statements for the cycles calculation.
#include"addressing.h"
//Holds address of current instruction.
void* current_instruction;
address fAddressGetAddress(Addressing mode, short x) {
switch(mode){
case eImplied:
case eIndirectAbsolute:
case eRelative:
case eImmediate:
case eAccumulator:
return 0x0000;
case eAbsolute:
return x;
case eAbsoluteIndexedX:
return x + X;
case eAbsoluteIndexedY:
return x + Y;
case eZeroPage:
return x & 0x00FF;
case eZeroPageIndexedX:
return ((x + X) & 0x00FF);
case eZeroPageIndexedY:
return ((x + Y) & 0x00FF);
case eIndexedIndirect:
return ((GetMemory(x+X+1))<<8) + (GetMemory(x+X));
case eIndirectIndexed:
return ((GetMemory(x+1))<<8) + (GetMemory(x)) + Y;
}
}
int fAddressGetLength(Addressing mode){
switch(mode){
case eAbsolute: case eAbsoluteIndexedX: case eAbsoluteIndexedY:
return 3;
case eAccumulator: case eImplied:
return 1;
default:
return 2;
}
}
byte fAddressGetValue(Addressing mode, short x, address addr) {
switch(mode){
case eImplied:
case eIndirectAbsolute:
case eRelative:
return 0;
case eImmediate:
return x;
case eAccumulator:
return acc;
default:
return GetMemory(addr);
}
}
int fAddressGetCycles(Addressing mode, short x, address addr) {
int cycles;
//case &fADC: case &fAND: case &fBIT: case &fCMP: case &fCPX: case &fCPY: case &fEOR: case &fLDA:
//case &fLDX: case &fLDY: case &fORA: case &fSBC: case &fSTX: case &fSTY:
if ( current_instruction == &fADC || current_instruction == &fAND || current_instruction == &fBIT || current_instruction == &fCMP || current_instruction == &fCPX
|| current_instruction == &fCPY || current_instruction == &fEOR || current_instruction == &fLDA || current_instruction == &fLDX || current_instruction == &fLDY
|| current_instruction == &fORA || current_instruction == &fSBC || current_instruction == &fSTX || current_instruction == &fSTY ){
switch(mode){
case eImmediate:
cycles = 2; break;
case eZeroPage:
cycles = 3; break;
case eZeroPageIndexedX: case eAbsolute: case eAbsoluteIndexedX: case eAbsoluteIndexedY:
cycles = 4; break;
case eIndexedIndirect:
cycles = 6; break;
case eIndirectIndexed:
cycles = 5; break;
}
}
//case &fASL: case &fDEC: case &fINC: case &fLSR: case &fROL: case &fROR:
else if( current_instruction == &fASL || current_instruction == &fDEC || current_instruction == &fINC
|| current_instruction == &fLSR || current_instruction == &fROL || current_instruction == &fROR ){
switch(mode){
case eAccumulator:
cycles = 2; break;
case eZeroPage:
cycles = 5; break;
case eZeroPageIndexedX: case eAbsolute:
cycles = 6; break;
case eAbsoluteIndexedX:
cycles = 7; break;
}
}
//case &fSTA:
else if (current_instruction == &fSTA){
switch(mode){
case eZeroPage:
cycles = 3; break;
case eZeroPageIndexedX: case eAbsolute:
cycles = 4; break;
case eAbsoluteIndexedX: case eAbsoluteIndexedY:
cycles = 5; break;
case eIndexedIndirect: case eIndirectIndexed:
cycles = 6; break;
}
}
//case &fBRK:
else if (current_instruction == &fBRK){
cycles = 7;
}
//case &fRTI: case &fRTS: case &fJSR:
else if (current_instruction == &fRTI || current_instruction == &fRTS || current_instruction == &fJSR){
cycles = 6;
}
//case &fJMP:
else if (current_instruction == &fJMP){
cycles = 5;
}
//case &fPLA: case &fPLP:
else if (current_instruction == &fPLA || current_instruction == &fPLP){
cycles = 4;
}
//case &fPHA: case &fPHP:
else if (current_instruction == &fPHA || current_instruction == &fPHP){
cycles = 3;
}
else {
cycles = 2;
}
// Page Boundary
//case &fADC: case &fSBC: case &fLDA: case &fLDX: case &fLDY: case &fEOR: case &fAND: case &fORA: case &fCMP:
if ( current_instruction == &fADC || current_instruction == &fSBC || current_instruction == &fLDA || current_instruction == &fLDX || current_instruction == &fLDY
|| current_instruction == &fEOR || current_instruction == &fAND || current_instruction == &fORA || current_instruction == &fCMP ){
switch(mode){
case eAbsoluteIndexedX:
if ((x & 0xFF00) != ((x + X) & 0xFF00))
cycles++;
break;
case eAbsoluteIndexedY:
if ((x & 0xFF00) != ((x + Y) & 0xFF00))
cycles++;
break;
case eIndirectIndexed:
if ((addr & 0xFF00) != (addr - Y & 0xFF00))
cycles++;
break;
}
}
return cycles;
}
AddData fAddress(Addressing mode, short x) {
AddData ret;
ret.add = fAddressGetAddress (mode, x);
ret.value = fAddressGetValue (mode, x, ret.add);
ret.length = fAddressGetLength (mode);
ret.cycles = fAddressGetCycles (mode, x, ret.add);
return ret;
}
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