1 files changed, 9 insertions, 21 deletions
diff --git a/nandgame/assembler/disas.py b/nandgame/assembler/disas.py
index 4994a69..21cd081 100755
--- a/nandgame/assembler/disas.py
+++ b/nandgame/assembler/disas.py
@@ -68,34 +68,22 @@ def decode_arg1(ins: int) -> str:
 
     if zx:
         return "0"
-    # and not sw?
-    # zx and swap: don't care, other arg is zeroed
-
-    if not zx and not sw and not use_mem:
-        return "A"
-    if not zx and not sw and use_mem:
-        return "M"
-
-    return "?"
+    if not sw:
+        return "D"
+    return "M" if use_mem else "A"
 
 
 # normally, Y = arg2 = A
 def decode_arg2(ins: int) -> str:
     use_mem = (ins & (1 << 12)) != 0
-    zx = (ins & (1 << 7)) != 0
-    sw = (ins & (1 << 6)) != 0
 
-    if zx and sw:
-        return "0"
-    # zx and not swap: don't care, other arg is zeroed
-
-    # zx ???
-    if sw and not use_mem:
-        return "A"
-    if sw and use_mem:
-        return "M"
+    # don't care, only X is zeroed
+    # zx = (ins & (1 << 7)) != 0
+    sw = (ins & (1 << 6)) != 0
 
-    return "?"
+    if sw:
+        return "D"
+    return "M" if use_mem else "A"
 
 
 def decode_dest(ins: int) -> str: