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LC: Support write-enabling LC via single 'INC abs,X' opcode for 6502 & 65C02. (#404, #700)

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tomcw 2019-10-12 22:34:35 +01:00
parent 3ba303a749
commit d39ba32e8a
1 changed files with 8 additions and 4 deletions
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12
source/LanguageCard.cpp
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@ -103,18 +103,22 @@ BYTE __stdcall LanguageCardUnit::IO(WORD PC, WORD uAddr, BYTE bWrite, BYTE uValu
return bWrite ? 0 : MemReadFloatingBus(nExecutedCycles);
}
// GH#700: INC $C083/C08B (RMW) to write enable the LC
bool LanguageCardUnit::IsOpcodeRMWabs(WORD addr)
{
if (GetMainCpu() != CPU_65C02)
return false;
BYTE param1 = mem[(regs.pc - 2) & 0xffff];
BYTE param2 = mem[(regs.pc - 1) & 0xffff];
if (param1 != (addr & 0xff) || param2 != 0xC0)
return false;
// GH#404, GH#700: INC $C083,X/C08B,X (RMW) to write enable the LC (any 6502/65C02/816)
BYTE opcode = mem[(regs.pc - 3) & 0xffff];
if (opcode == 0xFE && regs.x == 0) // INC abs,x
return true;
// GH#700: INC $C083/C08B (RMW) to write enable the LC (65C02 only)
if (GetMainCpu() != CPU_65C02)
return false;
if (opcode == 0xEE || // INC abs
opcode == 0xCE || // DEC abs
opcode == 0x6E || // ROR abs