From c4a9a10e09c76763787c88af567e0c19d1951798 Mon Sep 17 00:00:00 2001
From: MadMaurice <madmaurice@zom.bi>
Date: Tue, 29 Aug 2023 23:59:32 +0200
Subject: [PATCH] cpu/decoder - Treat undefined opcodes as NOP

---
 cpu/decoder.cpp | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/cpu/decoder.cpp b/cpu/decoder.cpp
index b47702b..7c6699f 100644
--- a/cpu/decoder.cpp
+++ b/cpu/decoder.cpp
@@ -300,7 +300,22 @@ void Cpu::executeInstruction()
     {
       switch(op)
         {
-        case 0x00: break; // NOP
+        case 0xD3: // Undefined, treat as NOP
+        case 0xE3:
+        case 0xE4:
+        case 0xF4:
+        case 0xDB:
+        case 0xEB:
+        case 0xEC:
+        case 0xFC:
+        case 0xDD:
+        case 0xED:
+        case 0xFD:
+          break;
+
+        case 0x00: // defined NOP
+          break;
+
         case 0x0A: // Load A, [BC]
           state.A = bus->read8(state.BC);
           mcycles = 2;