diff --git a/erlang/apps/sim/src/sim_boolean.erl b/erlang/apps/sim/src/sim_boolean.erl
index 0de888c..6d42675 100644
--- a/erlang/apps/sim/src/sim_boolean.erl
+++ b/erlang/apps/sim/src/sim_boolean.erl
@@ -43,6 +43,7 @@
         , handle_SETZB/4
         , handle_SETZM/4
         , handle_XOR/4
+        , handle_XORB/4
         , handle_XORI/4
         , handle_XORM/4
         ]).
@@ -330,6 +331,20 @@ handle_XORM(Core, Mem, IR, EA) ->
                           fun(Core1, Mem1) -> handle_XORM(Core1, Mem1, IR, EA) end)
   end.
 
+-spec handle_XORB(#core{}, sim_mem:mem(), IR :: word(), #ea{})
+      -> {#core{}, sim_mem:mem(), {ok, integer()} | {error, {module(), term()}}}.
+handle_XORB(Core, Mem, IR, EA) ->
+  case sim_core:c(Core, Mem, EA) of
+    {ok, CE} ->
+      AC = IR band 8#17,
+      CA = sim_core:get_ac(Core, AC),
+      Word = CE bxor CA,
+      handle_ANDB(Core, Mem, AC, EA, Word);
+    {error, Reason} ->
+      sim_core:page_fault(Core, Mem, ea_address(EA), read, Reason,
+                          fun(Core1, Mem1) -> handle_XORB(Core1, Mem1, IR, EA) end)
+  end.
+
 %% Miscellaneous ===============================================================
 
 ea_address(#ea{section = Section, offset = Offset}) ->
diff --git a/erlang/apps/sim/src/sim_core.erl b/erlang/apps/sim/src/sim_core.erl
index 2ebae29..ce4edfa 100644
--- a/erlang/apps/sim/src/sim_core.erl
+++ b/erlang/apps/sim/src/sim_core.erl
@@ -280,6 +280,7 @@ dispatch(Core, Mem, IR, EA) ->
     8#430 -> sim_boolean:handle_XOR(Core, Mem, IR, EA);
     8#431 -> sim_boolean:handle_XORI(Core, Mem, IR, EA);
     8#432 -> sim_boolean:handle_XORM(Core, Mem, IR, EA);
+    8#433 -> sim_boolean:handle_XORB(Core, Mem, IR, EA);
     _ ->
       PC = (Core#core.pc_section bsl 18) bor Core#core.pc_offset,
       {Core, Mem, {error, {?MODULE, {dispatch, PC, IR, EA}}}}
diff --git a/erlang/apps/sim/test/sim_boolean_tests.erl b/erlang/apps/sim/test/sim_boolean_tests.erl
index 7ccbf19..9ffa883 100644
--- a/erlang/apps/sim/test/sim_boolean_tests.erl
+++ b/erlang/apps/sim/test/sim_boolean_tests.erl
@@ -71,6 +71,7 @@
 -define(OP_XOR, 8#430).
 -define(OP_XORI, 8#431).
 -define(OP_XORM, 8#432).
+-define(OP_XORB, 8#433).
 
 %% 2.4 Boolean Functions =======================================================
 
@@ -411,6 +412,18 @@ xorm_test() ->
          [ {#ea{section = 1, offset = 8#200, islocal = false}, 8#434343} % C(1,,200) = 0,,434343
          ]).
 
+xorb_test() ->
+  Prog =
+    [ {1, 8#100, ?INSN(?OP_MOVEI, 1, 0, 0, 8#707070)} % 1,,100/ MOVEI 1,707070
+    , {1, 8#101, ?INSN(?OP_XORB, 1, 0, 0, 8#200)}     % 1,,101/ XORB 1,200
+    , {1, 8#102, ?INSN_INVALID}                       % 1,,102/ <invalid>
+    , {1, 8#200, ?COMMA2(0, 8#333333)}                % 1,,200/ 0,,333333
+    ],
+  expect(Prog, [], {1, 8#102}, ?DEFAULT_FLAGS,
+         [ {#ea{section = 1, offset = 8#200, islocal = false}, 8#434343} % C(1,,200) = 0,,434343
+         , {#ea{section = 1, offset = 1, islocal = false}, 8#434343} % AC1 = 0,,434343
+         ]).
+
 %% Common code to run short sequences ==========================================
 
 expect(Prog, ACs, ExpectedPC, ExpectedFlags, ExpectedEs) ->