Fixed a bug in some illegal opcodes.

Author: ooPo

build-and-run.sh

@@ -0,0 +1,5 @@
+#!/bin/bash
+
+cmake --preset default          # Configure (output in build/)
+cmake --build --preset default  # Build
+cmake --build --preset run      # Build and run the NES example against the test ROM

src/MOS6502.cpp

@@ -3,6 +3,7 @@
 // by Naomi Peori (naomi@peori.ca)
 //
 
+#include <functional>
 #include "MOS6502/MOS6502.h"
 
 void MOS6502::Run() {

src/MOS6502_illegal.cpp

@@ -3,6 +3,7 @@
 // by Naomi Peori (naomi@peori.ca)
 //
 
+#include <functional>
 #include "MOS6502/MOS6502.h"
 
 //
@@ -62,47 +63,104 @@ void MOS6502::RunIllegal(BYTE opcode) {
 
     // ---------------------------------------------------------------
     // SHY — Store Y & (addr_high + 1), Absolute, X
+    // On page-cross the effective address's high byte is corrupted to v.
     // ---------------------------------------------------------------
 
     case 0x9C: {
       AB.l = Fetch();
       AB.h = Fetch();
-      BYTE v = Y & (AB.h + 1);
+      BYTE argHigh = AB.h;
+      BYTE v       = Y & (argHigh + 1);
       AB = IdleOnPageAlways(AB, X);
       PollInterrupts();
+      if (AB.h != argHigh) { AB.h = v; }
       Store(AB.w, v);
       break;
     }
 
     // ---------------------------------------------------------------
     // SHX — Store X & (addr_high + 1), Absolute, Y
+    // On page-cross the effective address's high byte is corrupted to v.
     // ---------------------------------------------------------------
 
     case 0x9E: {
       AB.l = Fetch();
       AB.h = Fetch();
-      BYTE v = X & (AB.h + 1);
+      BYTE argHigh = AB.h;
+      BYTE v       = X & (argHigh + 1);
       AB = IdleOnPageAlways(AB, Y);
       PollInterrupts();
+      if (AB.h != argHigh) { AB.h = v; }
       Store(AB.w, v);
       break;
     }
 
     // ---------------------------------------------------------------
     // TAS — S = A & X; store S & (addr_high + 1), Absolute, Y
+    // On page-cross the effective address's high byte is corrupted to v.
     // ---------------------------------------------------------------
 
     case 0x9B: {
       AB.l = Fetch();
       AB.h = Fetch();
+      BYTE argHigh = AB.h;
       S = A & X;
-      BYTE v = S & (AB.h + 1);
+      BYTE v = S & (argHigh + 1);
       AB = IdleOnPageAlways(AB, Y);
       PollInterrupts();
+      if (AB.h != argHigh) { AB.h = v; }
       Store(AB.w, v);
       break;
     }
 
+    // ---------------------------------------------------------------
+    // SHA — Store A & X & (addr_high + 1)
+    // On page-cross the effective address's high byte is corrupted to v.
+    // ---------------------------------------------------------------
+
+    case 0x9F: { // Absolute, Y
+      AB.l = Fetch();
+      AB.h = Fetch();
+      BYTE argHigh = AB.h;
+      BYTE v       = A & X & (argHigh + 1);
+      AB = IdleOnPageAlways(AB, Y);
+      PollInterrupts();
+      if (AB.h != argHigh) { AB.h = v; }
+      Store(AB.w, v);
+      break;
+    }
+
+    case 0x93: { // Indirect, Y
+      TB.w  = Fetch();
+      AB.l  = Load(TB.w);
+      TB.l += 1;
+      AB.h  = Load(TB.w);
+      BYTE argHigh = AB.h;
+      BYTE v       = A & X & (argHigh + 1);
+      AB = IdleOnPageAlways(AB, Y);
+      PollInterrupts();
+      if (AB.h != argHigh) { AB.h = v; }
+      Store(AB.w, v);
+      break;
+    }
+
+    // ---------------------------------------------------------------
+    // ANE / XAA — A = (A | magic) & X & #imm  (unstable on hardware)
+    // LXA       — A = X = (A | magic) & #imm  (unstable on hardware)
+    // The "magic" constant varies by die/temperature; 0xEE is the value
+    // Blargg's test ROMs assume.
+    // ---------------------------------------------------------------
+
+    case 0x8B:
+      PollInterrupts();
+      A = Flags((A | 0xEE) & X & Fetch());
+      break;
+
+    case 0xAB:
+      PollInterrupts();
+      A = X = Flags((A | 0xEE) & Fetch());
+      break;
+
     // ---------------------------------------------------------------
     // DCP — DEC, then CMP
     // ---------------------------------------------------------------