diff --git a/erlang/apps/sim/src/sim_core.erl b/erlang/apps/sim/src/sim_core.erl
index 5da396f..f828484 100644
--- a/erlang/apps/sim/src/sim_core.erl
+++ b/erlang/apps/sim/src/sim_core.erl
@@ -337,6 +337,10 @@ dispatch(Core, Mem, IR, EA) ->
     8#521 -> sim_halfword:handle_HLLOI(Core, Mem, IR, EA);
     8#522 -> sim_halfword:handle_HLLOM(Core, Mem, IR, EA);
     8#523 -> sim_halfword:handle_HLLOS(Core, Mem, IR, EA);
+    8#524 -> sim_halfword:handle_HRLO(Core, Mem, IR, EA);
+    8#525 -> sim_halfword:handle_HRLOI(Core, Mem, IR, EA);
+    8#526 -> sim_halfword:handle_HRLOM(Core, Mem, IR, EA);
+    8#527 -> sim_halfword:handle_HRLOS(Core, Mem, IR, EA);
     8#530 -> sim_halfword:handle_HLLE(Core, Mem, IR, EA);
     8#531 -> sim_boolean:handle_SETZ(Core, Mem, IR, EA); % HLLEI = HLLZI = SETZ
     8#532 -> sim_halfword:handle_HLLEM(Core, Mem, IR, EA);
diff --git a/erlang/apps/sim/src/sim_halfword.erl b/erlang/apps/sim/src/sim_halfword.erl
index fc44b25..83f56a9 100644
--- a/erlang/apps/sim/src/sim_halfword.erl
+++ b/erlang/apps/sim/src/sim_halfword.erl
@@ -41,6 +41,10 @@
         , handle_HRL/4
         , handle_HRLI/4
         , handle_HRLM/4
+        , handle_HRLO/4
+        , handle_HRLOI/4
+        , handle_HRLOM/4
+        , handle_HRLOS/4
         , handle_HRLS/4
         , handle_HRLZ/4
         , handle_HRLZM/4
@@ -314,6 +318,49 @@ handle_HRLZS(Core, Mem, IR, EA) ->
                           fun(Core1, Mem1) -> ?FUNCTION_NAME(Core1, Mem1, IR, EA) end)
   end.
 
+%% HRLO - Half Word Right to Left, Ones
+
+-spec handle_HRLO(#core{}, sim_mem:mem(), IR :: word(), #ea{})
+      -> {#core{}, sim_mem:mem(), {ok, integer()} | {error, {module(), term()}}}.
+handle_HRLO(Core, Mem, IR, EA) ->
+  case sim_core:c(Core, Mem, EA) of
+    {ok, CE} ->
+      AC = IR band 8#17,
+      Word = set_left_ones(get_right(CE)),
+      sim_core:next_pc(sim_core:set_ac(Core, AC, Word), Mem);
+    {error, Reason} ->
+      sim_core:page_fault(Core, Mem, ea_address(EA), read, Reason,
+                          fun(Core1, Mem1) -> ?FUNCTION_NAME(Core1, Mem1, IR, EA) end)
+  end.
+
+-spec handle_HRLOI(#core{}, sim_mem:mem(), IR :: word(), #ea{})
+      -> {#core{}, sim_mem:mem(), {ok, integer()} | {error, {module(), term()}}}.
+handle_HRLOI(Core, Mem, IR, EA) ->
+  AC = IR band 8#17,
+  Word = set_left_ones(EA#ea.offset),
+  sim_core:next_pc(sim_core:set_ac(Core, AC, Word), Mem).
+
+-spec handle_HRLOM(#core{}, sim_mem:mem(), IR :: word(), #ea{})
+      -> {#core{}, sim_mem:mem(), {ok, integer()} | {error, {module(), term()}}}.
+handle_HRLOM(Core, Mem, IR, EA) ->
+  AC = IR band 8#17,
+  CA = sim_core:get_ac(Core, AC),
+  Word = set_left_ones(get_right(CA)),
+  handle_writeback(Core, Mem, EA, Word).
+
+-spec handle_HRLOS(#core{}, sim_mem:mem(), IR :: word(), #ea{})
+      -> {#core{}, sim_mem:mem(), {ok, integer()} | {error, {module(), term()}}}.
+handle_HRLOS(Core, Mem, IR, EA) ->
+  case sim_core:c(Core, Mem, EA) of
+    {ok, CE} ->
+      AC = IR band 8#17,
+      Word = set_left_ones(get_right(CE)),
+      handle_writeback(Core, Mem, AC, EA, Word);
+    {error, Reason} ->
+      sim_core:page_fault(Core, Mem, ea_address(EA), read, Reason,
+                          fun(Core1, Mem1) -> ?FUNCTION_NAME(Core1, Mem1, IR, EA) end)
+  end.
+
 %% Miscellaneous ===============================================================
 
 handle_writeback(Core, Mem, EA, Word) ->
diff --git a/erlang/apps/sim/test/sim_halfword_tests.erl b/erlang/apps/sim/test/sim_halfword_tests.erl
index 8ef9cde..8ed7b53 100644
--- a/erlang/apps/sim/test/sim_halfword_tests.erl
+++ b/erlang/apps/sim/test/sim_halfword_tests.erl
@@ -65,6 +65,10 @@
 -define(OP_HLLOI, 8#521).
 -define(OP_HLLOM, 8#522).
 -define(OP_HLLOS, 8#523).
+-define(OP_HRLO,  8#524).
+-define(OP_HRLOI, 8#525).
+-define(OP_HRLOM, 8#526).
+-define(OP_HRLOS, 8#527).
 -define(OP_HLLE,  8#530).
 -define(OP_HLLEI, 8#531).
 -define(OP_HLLEM, 8#532).
@@ -443,6 +447,64 @@ hrlzs_no_ac_test() ->
          , {#ea{section = 1, offset = 0, islocal = false}, ?COMMA2(0, 1)} % AC0 = 0,,1
          ]).
 
+%% HRLO - Half Word Right to Left, Ones
+
+hrlo_test() ->
+  Prog =
+    [ {1, 8#100, ?INSN(?OP_MOVEI, 1, 0, 0, 1)}     % 1,,100/ MOVEI 1,1
+    , {1, 8#101, ?INSN(?OP_HRLO, 1, 0, 0, 8#200)}  % 1,,101/ HRLO 1,200
+    , {1, 8#102, ?INSN_INVALID}                    % 1,,102/ <invalid>
+    , {1, 8#200, ?COMMA2(0, 1)}                    % 1,,200/ 0,,1
+    ],
+  expect(Prog, [], {1, 8#102}, ?DEFAULT_FLAGS,
+         [ {#ea{section = 1, offset = 1, islocal = false}, ?COMMA2(1, -1)} % AC1 = 1,,-1
+         ]).
+
+hrloi_test() ->
+  Prog =
+    [ {1, 8#100, ?INSN(?OP_MOVEI, 1, 0, 0, 1)}     % 1,,100/ MOVEI 1,1
+    , {1, 8#101, ?INSN(?OP_HRLOI, 1, 0, 0, 1)}     % 1,,101/ HRLOI 1,1
+    , {1, 8#102, ?INSN_INVALID}                    % 1,,102/ <invalid>
+    ],
+  expect(Prog, [], {1, 8#102}, ?DEFAULT_FLAGS,
+         [ {#ea{section = 1, offset = 1, islocal = false}, ?COMMA2(1, -1)} % AC1 = 1,,-1
+         ]).
+
+hrlom_test() ->
+  Prog =
+    [ {1, 8#100, ?INSN(?OP_MOVEI, 1, 0, 0, 1)}     % 1,,100/ MOVEI 1,1
+    , {1, 8#101, ?INSN(?OP_HRLOM, 1, 0, 0, 8#200)} % 1,,101/ HRLOM 1,200
+    , {1, 8#102, ?INSN_INVALID}                    % 1,,102/ <invalid>
+    , {1, 8#200, ?COMMA2(0, 1)}                    % 1,,200/ 0,,1
+    ],
+  expect(Prog, [], {1, 8#102}, ?DEFAULT_FLAGS,
+         [ {#ea{section = 1, offset = 8#200, islocal = false}, ?COMMA2(1, -1)} % C(1,,200) = 1,,-1
+         ]).
+
+hrlos_ac_test() ->
+  Prog =
+    [ {1, 8#100, ?INSN(?OP_MOVEI, 1, 0, 0, 1)}     % 1,,100/ MOVEI 1,1
+    , {1, 8#101, ?INSN(?OP_HRLOS, 1, 0, 0, 8#200)} % 1,,101/ HRLOS 1,200
+    , {1, 8#102, ?INSN_INVALID}                    % 1,,102/ <invalid>
+    , {1, 8#200, ?COMMA2(0, 1)}                    % 1,,200/ 0,,1
+    ],
+  expect(Prog, [], {1, 8#102}, ?DEFAULT_FLAGS,
+         [ {#ea{section = 1, offset = 8#200, islocal = false}, ?COMMA2(1, -1)} % C(1,,200) = 1,,-1
+         , {#ea{section = 1, offset = 1, islocal = false}, ?COMMA2(1, -1)} % AC1 = 1,,-1
+         ]).
+
+hrlos_no_ac_test() ->
+  Prog =
+    [ {1, 8#100, ?INSN(?OP_MOVEI, 0, 0, 0, 1)}     % 1,,100/ MOVEI 0,1
+    , {1, 8#101, ?INSN(?OP_HRLOS, 0, 0, 0, 8#200)} % 1,,101/ HRLOS 0,200
+    , {1, 8#102, ?INSN_INVALID}                    % 1,,102/ <invalid>
+    , {1, 8#200, ?COMMA2(0, 1)}                    % 1,,200/ 0,,1
+    ],
+  expect(Prog, [], {1, 8#102}, ?DEFAULT_FLAGS,
+         [ {#ea{section = 1, offset = 8#200, islocal = false}, ?COMMA2(1, -1)} % C(1,,200) = 1,,-1
+         , {#ea{section = 1, offset = 0, islocal = false}, ?COMMA2(0, 1)} % AC0 = 0,,1
+         ]).
+
 %% Common code to run short sequences ==========================================
 
 expect(Prog, ACs, ExpectedPC, ExpectedFlags, ExpectedEs) ->