diff --git a/src/kyupy/logic_sim.py b/src/kyupy/logic_sim.py
index b6d20a4..f4d9fb5 100644
--- a/src/kyupy/logic_sim.py
+++ b/src/kyupy/logic_sim.py
@@ -89,10 +89,9 @@ class LogicSim(sim.SimOps):
                     elif op == sim.NOR2: self.c[o0] = ~(self.c[i0] | self.c[i1])
                     elif op == sim.XOR2: self.c[o0] = self.c[i0] ^ self.c[i1]
                     elif op == sim.XNOR2: self.c[o0] = ~(self.c[i0] ^ self.c[i1])
+                    elif op == sim.AOI21: self.c[o0] = ~((self.c[i0] & self.c[i1]) | self.c[i2])
                     else: print(f'unknown op {op}')
                     inject_cb(o0, self.s[o0])
-        elif self.m == 4:
-            pass
         else:
             for op, o0, i0, i1, i2, i3 in self.ops:
                 o0, i0, i1, i2, i3 = [self.c_locs[x] for x in (o0, i0, i1, i2, i3)]
@@ -104,6 +103,7 @@ class LogicSim(sim.SimOps):
                 elif op == sim.NOR2: logic.bp_or(self.c[o0], self.c[i0], self.c[i1]); logic.bp_not(self.c[o0], self.c[o0])
                 elif op == sim.XOR2: logic.bp_xor(self.c[o0], self.c[i0], self.c[i1])
                 elif op == sim.XNOR2: logic.bp_xor(self.c[o0], self.c[i0], self.c[i1]); logic.bp_not(self.c[o0], self.c[o0])
+                elif op == sim.AOI21: logic.bp_and(self.c[self.tmp_idx], self.c[i0], self.c[i1]); logic.bp_or(self.c[o0], self.c[self.tmp_idx], self.c[i2]); logic.bp_not(self.c[o0], self.c[o0])
                 else: print(f'unknown op {op}')
                 if inject_cb is not None: inject_cb(o0, self.s[o0])
 
@@ -145,4 +145,5 @@ def _prop_cpu(ops, c_locs, c):
         elif op == sim.NOR2: c[o0] = ~(c[i0] | c[i1])
         elif op == sim.XOR2: c[o0] = c[i0] ^ c[i1]
         elif op == sim.XNOR2: c[o0] = ~(c[i0] ^ c[i1])
+        elif op == sim.AOI21: c[o0] = ~((c[i0] & c[i1]) | c[i2])
         else: print(f'unknown op {op}')