Method GetOpcodeCyclesForWrite

source/6522.cpp:498–570

TODO: RMW opcodes: dec,inc,asl,lsr,rol,ror (abs16 & abs16,x) + 65C02 trb,tsb (abs16)

// TODO: RMW opcodes: dec,inc,asl,lsr,rol,ror (abs16 & abs16,x) + 65C02 trb,tsb (abs16)
UINT SY6522::GetOpcodeCyclesForWrite(BYTE reg)
{
	UINT zpOpcodeCycles = 0, opcodeCycles = 0;
	BYTE zpOpcode = 0, opcode = 0;	// these double-up as flags to indicate validity
	bool abs16x = false;
	bool abs16y = false;
	bool indx = false;
	bool indy = false;

	const BYTE opcodeMinus3 = ReadByteFromMemory(::regs.pc - 3);
	const BYTE opcodeMinus2 = ReadByteFromMemory(::regs.pc - 2);

	// Check 2-byte opcodes
	if (opcodeMinus2 == 0x81)			// sta (zp,x)
	{
		zpOpcodeCycles = 6;
		zpOpcode = opcodeMinus2;
		indx = true;
	}
	else if (opcodeMinus2 == 0x91)		// sta (zp),y
	{	// Eg. FT demos: OMT, PLS
		zpOpcodeCycles = 6;
		zpOpcode = opcodeMinus2;
		indy = true;
	}
	else if (opcodeMinus2 == 0x92 && GetMainCpu() == CPU_65C02)		// sta (zp) : 65C02-only
	{
		zpOpcodeCycles = 5;
		zpOpcode = opcodeMinus2;
	}

	// Check 3-byte opcodes
	if ((opcodeMinus3 == 0x8C) ||		// sty abs16
		(opcodeMinus3 == 0x8D) ||		// sta abs16
		(opcodeMinus3 == 0x8E))			// stx abs16
	{	// Eg. FT demos: CHIP, MADEF, MAD2
		opcodeCycles = 4;
		opcode = opcodeMinus3;
	}
	else if (opcodeMinus3 == 0x99)		// sta abs16,y
	{
		opcodeCycles = 5;
		opcode = opcodeMinus3;
		abs16y = true;
	}
	else if (opcodeMinus3 == 0x9D)		// sta abs16,x
	{	// Eg. Paleotronic microTracker demo
		opcodeCycles = 5;
		opcode = opcodeMinus3;
		abs16x = true;
	}
	else if (opcodeMinus3 == 0x9C && GetMainCpu() == CPU_65C02)		// stz abs16 : 65C02-only
	{
		opcodeCycles = 4;
		opcode = opcodeMinus3;
	}
	else if (opcodeMinus3 == 0x9E && GetMainCpu() == CPU_65C02)		// stz abs16,x : 65C02-only
	{