6502/EightBit
1
0
Fork 0
mirror of https://github.com/MoleskiCoder/EightBit.git synced 2024-06-11 10:29:31 +00:00
Code Issues Projects Releases Wiki Activity

Add undocumented instructions SYA and SXA to M6502 implementation

Browse Source
This commit is contained in:
Adrian Conlon 2024-01-06 09:52:17 +00:00
parent c15f7f836e
commit 349bada9cc
2 changed files with 21 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
M6502/inc/mos6502.h
View File

@ -257,6 +257,12 @@ namespace EightBit {
sre(memoryRead());
}
// SYA
void sya_AbsoluteX() noexcept;
// SXA
void sxa_AbsoluteY() noexcept;
// NOP
void nop_AbsoluteX() noexcept;

18
M6502/src/mos6502.cpp
View File

@ -2,7 +2,7 @@
#include "../inc/mos6502.h"
EightBit::MOS6502::MOS6502(Bus& bus) noexcept
: LittleEndianProcessor(bus) {
: LittleEndianProcessor(bus) {
RaisedPOWER.connect([this](EventArgs) {
X() = Bit7;
Y() = 0;
@ -277,9 +277,9 @@ int EightBit::MOS6502::execute() noexcept {
case 0x99: sta_AbsoluteY(); break; // STA (absolute, Y)
case 0x9a: memoryRead(PC()); S() = X(); break; // TXS (implied)
case 0x9b: break;
case 0x9c: break;
case 0x9c: sya_AbsoluteX(); break; // *SYA (absolute, X)
case 0x9d: sta_AbsoluteX(); break; // STA (absolute, X)
case 0x9e: break;
case 0x9e: sxa_AbsoluteY(); break; // *SXA (absolute, Y)
case 0x9f: break;
case 0xa0: Y() = through(AM_Immediate()); break; // LDY (immediate)
@ -853,6 +853,18 @@ void EightBit::MOS6502::sre_IndirectIndexedY() noexcept {
sre_with_fixup(address, page);
}
void EightBit::MOS6502::sya_AbsoluteX() noexcept {
const auto [address, page] = Address_AbsoluteX();
fixup(address, page);
memoryWrite(Y() & (address.high + 1));
}
void EightBit::MOS6502::sxa_AbsoluteY() noexcept {
const auto [address, page] = Address_AbsoluteY();
fixup(address, page);
memoryWrite(X() & (address.high + 1));
}
void EightBit::MOS6502::nop_AbsoluteX() noexcept {
const auto [address, page] = Address_AbsoluteX();
fixup(address, page);