diff --git a/src/cpu.verilog b/src/cpu.verilog
index aa58a89..47c825a 100644
--- a/src/cpu.verilog
+++ b/src/cpu.verilog
@@ -90,6 +90,7 @@ localparam
     logic [1:0]  pending_y_read;
     logic        pending_rel_branch;
     logic        pending_nz_alu_update;
+    logic        pending_c_alu_update;
     wire         is_arith;
     logic [2:0]  extra_timing;
     reg [3:0]  state_after_delay;
@@ -107,6 +108,7 @@ initial pending_x_read = 0;
 initial pending_y_read = 0;
 initial pending_rel_branch = 0;
 initial pending_nz_alu_update = 0;
+initial pending_c_alu_update = 0;
 initial mem_aux_addr = 0;
 initial instr = 0;
 initial extra_timing = 0;
@@ -234,6 +236,46 @@ always_comb
             alu_op_c = 1'b1;
             alu_op_sel = OP_SUB;
         end
+      else if (decoded_instr == I_ASL)
+        begin
+            if (address_code == ADDR_MODE_IMPLIED)
+              alu_op_1 = A;
+            else
+              alu_op_1 = mem_data;
+            alu_op_2 = SHIFT_LEFT;
+            alu_op_c = 0;
+            alu_op_sel = OP_SHF;
+        end
+      else if (decoded_instr == I_LSR)
+        begin
+            if (address_code == ADDR_MODE_IMPLIED)
+              alu_op_1 = A;
+            else
+              alu_op_1 = mem_data;
+            alu_op_2 = SHIFT_RIGHT;
+            alu_op_c = 0;
+            alu_op_sel = OP_SHF;
+        end
+      else if (decoded_instr == I_ROL)
+        begin
+            if (address_code == ADDR_MODE_IMPLIED)
+              alu_op_1 = A;
+            else
+              alu_op_1 = mem_data;
+            alu_op_2 = SHIFT_LEFT;
+            alu_op_c = P[P_C];
+            alu_op_sel = OP_ROT;
+        end
+      else if (decoded_instr == I_ROR)
+        begin
+            if (address_code == ADDR_MODE_IMPLIED)
+              alu_op_1 = A;
+            else
+              alu_op_1 = mem_data;
+            alu_op_2 = SHIFT_RIGHT;
+            alu_op_c = P[P_C];
+            alu_op_sel = OP_ROT;
+        end
       else
         begin
             alu_op_1 = A;
@@ -333,6 +375,12 @@ always @(posedge clk)
                 end
               pending_nz_alu_update <= 0;
 
+              if (pending_c_alu_update)
+                begin
+                    P[P_C] <= alu_c;
+                end
+              pending_c_alu_update <= 0;
+
               PC <= PC + 1;
               state <= STATE_EXECUTE;
           end
@@ -383,7 +431,11 @@ always @(posedge clk)
           begin
               mem_sel <= DMUX_AUX;
               if (decoded_instr == I_INC ||
-                  decoded_instr == I_DEC)
+                  decoded_instr == I_DEC ||
+                  decoded_instr == I_ASL ||
+                  decoded_instr == I_LSR ||
+                  decoded_instr == I_ROL ||
+                  decoded_instr == I_ROR )
                 begin
                     state <= STATE_READ_ADDR_ZP;
                 end
@@ -397,7 +449,11 @@ always @(posedge clk)
           begin
               mem_sel <= DMUX_AUX;
               if (decoded_instr == I_INC ||
-                  decoded_instr == I_DEC)
+                  decoded_instr == I_DEC ||
+                  decoded_instr == I_ASL ||
+                  decoded_instr == I_LSR ||
+                  decoded_instr == I_ROL ||
+                  decoded_instr == I_ROR)
                 begin
                     state <= STATE_READ_ADDR_ZP;
                 end
@@ -432,6 +488,14 @@ always @(posedge clk)
                     pending_y_read <= READ_SOURCE_ALU;
                     state <= STATE_FETCH;
                 end
+              else if (decoded_instr == I_ASL || decoded_instr == I_LSR ||
+                       decoded_instr == I_ROL || decoded_instr == I_ROR)
+                begin
+                    pending_a_read <= READ_SOURCE_ALU;
+                    pending_nz_alu_update <= 1;
+                    pending_c_alu_update <= 1;
+                    state <= STATE_FETCH;
+                    end
           end
         else if (decoded_instr == I_BNE)
           begin
@@ -487,8 +551,13 @@ always @(posedge clk)
               pending_a_read <= READ_SOURCE_ALU;
           end
         else if (decoded_instr == I_DEC ||
-                 decoded_instr == I_INC)
+                 decoded_instr == I_INC ||
+                 decoded_instr == I_ASL ||
+                 decoded_instr == I_LSR ||
+                 decoded_instr == I_ROL ||
+                 decoded_instr == I_ROR)
         begin
+            pending_c_alu_update <= 1;
             pending_nz_alu_update <= 1'b1;
         end
 
@@ -541,7 +610,9 @@ always @(posedge clk)
         mem_aux_addr[7:0] <= mem_data;
         mem_sel <= DMUX_AUX;
 
-        if (decoded_instr == I_DEC || decoded_instr == I_INC)
+        if (decoded_instr == I_DEC || decoded_instr == I_INC ||
+            decoded_instr == I_ASL || decoded_instr == I_LSR ||
+            decoded_instr == I_ROL || decoded_instr == I_ROR)
           begin
               state <= STATE_EXECUTE_ABS_ALU;
           end
@@ -609,6 +680,12 @@ always @(posedge clk)
           begin
               extra_timing <= 1;
           end
+        if (decoded_instr == I_ASL || decoded_instr == I_LSR ||
+            decoded_instr == I_ROL || decoded_instr == I_ROR)
+          begin
+              pending_nz_alu_update <= 1;
+              pending_c_alu_update <= 1;
+          end
     end
   else if (state == STATE_WRITE_ABS_ALU)
     begin
@@ -660,7 +737,11 @@ always_comb
                   mem_data_wr = Y;
               end
             else if(decoded_instr == I_DEC ||
-                    decoded_instr == I_INC)
+                    decoded_instr == I_INC ||
+                    decoded_instr == I_ASL ||
+                    decoded_instr == I_LSR ||
+                    decoded_instr == I_ROL ||
+                    decoded_instr == I_ROR)
               begin
                   mem_wr = 1'b1;
                   mem_data_wr = alu_op_result;
@@ -1248,6 +1329,146 @@ always @(posedge clk)
           assert(Y == f_prev_Y);
       end
 
+always @(posedge clk)
+  if (f_prev_valid && state == STATE_EXECUTE)
+    if (f_prev_instruction == I_ASL || f_prev_instruction == I_LSR ||
+        f_prev_instruction == I_ROL || f_prev_instruction == I_ROR)
+      begin
+          cover(f_prev_addr_code == ADDR_MODE_IMPLIED);
+          cover(f_prev_addr_code == ADDR_MODE_ZP);
+          cover(f_prev_addr_code == ADDR_MODE_INDEXED_ZP);
+          cover(f_prev_addr_code == ADDR_MODE_ABSOLUTE);
+          cover(f_prev_addr_code == ADDR_MODE_INDEXED_ABSOLUTE_X);
+
+          if (f_prev_addr_code != ADDR_MODE_IMPLIED)
+            begin
+                assert($past(mem_wr, 2) == 1'b1);
+            end
+
+          if (f_prev_instruction == I_ASL)
+            begin
+                if (f_prev_addr_code == ADDR_MODE_IMPLIED)
+                  begin
+                      assert(f_prev_A[6:0] == A[7:1]);
+                      assert(A[0] == 0);
+
+                      assert(f_prev_A[7] == P[P_C]);
+                      assert((A == 0) == P[P_Z]);
+                      assert(A[7] == P[P_N]);
+                  end
+                else
+                  begin
+                      assert($past(mem_data_wr[7:1], 2) == $past(mem_data[6:0], 2));
+                      assert($past(mem_data_wr[0], 2) == 0);
+
+                      assert($past(mem_data[7], 2) == P[P_C]);
+                      assert(($past(mem_data_wr, 2) == 0) == P[P_Z]);
+                      assert($past(mem_data_wr[7], 2) == P[P_N]);
+
+                      assert(A == f_prev_A);
+                  end
+            end
+          else if (f_prev_instruction == I_LSR)
+            begin
+                if (f_prev_addr_code == ADDR_MODE_IMPLIED)
+                  begin
+                      assert(f_prev_A[7:1] == A[6:0]);
+                      assert(A[7] == 0);
+
+                      assert(f_prev_A[0] == P[P_C]);
+                      assert((A == 0) == P[P_Z]);
+                      assert(A[7] == P[P_N]);
+                  end
+                else
+                  begin
+                      assert($past(mem_data_wr[6:0], 2) == $past(mem_data[7:1], 2));
+                      assert($past(mem_data_wr[7], 2) == 0);
+
+                      assert($past(mem_data[0], 2) == P[P_C]);
+                      assert(($past(mem_data_wr, 2) == 0) == P[P_Z]);
+                      assert($past(mem_data_wr[7], 2) == P[P_N]);
+
+                      assert(A == f_prev_A);
+                  end
+            end
+          else if (f_prev_instruction == I_ROR)
+            begin
+                if (f_prev_addr_code == ADDR_MODE_IMPLIED)
+                  begin
+                      assert(f_prev_A[7:1] == A[6:0]);
+                      assert(A[7] == f_prev_P[P_C]);
+
+                      assert(f_prev_A[0] == P[P_C]);
+                      assert((A == 0) == P[P_Z]);
+                      assert(A[7] == P[P_N]);
+                  end
+                else
+                  begin
+                      assert($past(mem_data_wr[6:0], 2) == $past(mem_data[7:1], 2));
+                      assert($past(mem_data_wr[7], 2) == f_prev_P[P_C]);
+
+                      assert($past(mem_data[0], 2) == P[P_C]);
+                      assert(($past(mem_data_wr, 2) == 0) == P[P_Z]);
+                      assert($past(mem_data_wr[7], 2) == P[P_N]);
+
+                      assert(A == f_prev_A);
+                  end
+            end
+          else if (f_prev_instruction == I_ROL)
+            begin
+                if (f_prev_addr_code == ADDR_MODE_IMPLIED)
+                  begin
+                      assert(f_prev_A[6:0] == A[7:1]);
+                      assert(A[0] == f_prev_P[P_C]);
+
+                      assert(f_prev_A[7] == P[P_C]);
+                      assert((A == 0) == P[P_Z]);
+                      assert(A[7] == P[P_N]);
+                  end
+                else
+                  begin
+                      assert($past(mem_data_wr[7:1], 2) == $past(mem_data[6:0], 2));
+                      assert($past(mem_data_wr[0], 2) == f_prev_P[P_C]);
+
+                      assert($past(mem_data[7], 2) == P[P_C]);
+                      assert(($past(mem_data_wr, 2) == 0) == P[P_Z]);
+                      assert($past(mem_data_wr[7], 2) == P[P_N]);
+
+                      assert(A == f_prev_A);
+                  end
+            end
+
+          if ($past(address_code) == ADDR_MODE_IMPLIED)
+            begin
+                assert($past(PC) == $past(f_prev_PC) + 16'd1);
+                assert(f_prev_instr_cycles == 2);
+            end
+          else if ($past(address_code) == ADDR_MODE_ZP)
+            begin
+                assert($past(PC) == $past(f_prev_PC) + 16'd2);
+                assert(f_prev_instr_cycles == 5);
+            end
+          else if ($past(address_code) == ADDR_MODE_INDEXED_ZP)
+            begin
+                assert($past(PC) == $past(f_prev_PC) + 16'd2);
+                assert(f_prev_instr_cycles == 6);
+            end
+          else if ($past(address_code) == ADDR_MODE_ABSOLUTE)
+            begin
+                assert($past(PC) == $past(f_prev_PC) + 16'd3);
+                assert(f_prev_instr_cycles == 6);
+            end
+          else if ($past(address_code) == ADDR_MODE_INDEXED_ABSOLUTE_X)
+            begin
+                assert($past(PC) == $past(f_prev_PC) + 16'd3);
+                assert(f_prev_instr_cycles == 7);
+            end
+
+          assert(S == f_prev_S);
+          assert(X == f_prev_X);
+          assert(Y == f_prev_Y);
+      end
+
 always @(posedge clk)
     if (f_past_valid)
 begin
@@ -1268,6 +1489,10 @@ begin
              decoded_instr == I_INY ||
              decoded_instr == I_DEC ||
              decoded_instr == I_INC ||
+             decoded_instr == I_ASL ||
+             decoded_instr == I_LSR ||
+             decoded_instr == I_ROR ||
+             decoded_instr == I_ROL ||
              decoded_instr == I_BNE ||
              decoded_instr == I_JMP
 );