diff --git a/ch4/motorcontrol.sv b/ch4/motorcontrol.sv
index d66eb83..3539434 100644
--- a/ch4/motorcontrol.sv
+++ b/ch4/motorcontrol.sv
@@ -1,3 +1,5 @@
+`timescale 1ns/1ps
+
 module motorcontrol #(parameter N=21)
    (input logic clk,
     input logic rst,
@@ -37,6 +39,11 @@ module motorcontrol #(parameter N=21)
 					pwm = 0; 
 					next_state = state;
 				end 
+			default: 
+				begin
+					pwm = 0; 
+					next_state = reset;
+				end 
 		endcase
 	end
 endmodule
diff --git a/ch4/motorcontrol_tb.sv b/ch4/motorcontrol_tb.sv
index 1f71d1e..5894a36 100644
--- a/ch4/motorcontrol_tb.sv
+++ b/ch4/motorcontrol_tb.sv
@@ -18,12 +18,15 @@ module motorcontrol_tb();
       clk = 0;
 
    initial begin
-                rst = 1; direction = 0;   
-     #10;       rst = 0; 
-     #19999990; rst = 1; direction = 1;
-     #10;       rst = 0;
-     #19999990; rst = 1;                              
-     #10;       rst = 0;
+      $dumpfile("output.vcd");
+      $dumpvars;
+      rst = 1; direction = 0;   
+      #10;       rst = 0; 
+      #19999990; rst = 1; direction = 1;
+      #10;       rst = 0;
+      #19999990; rst = 1;                              
+      #10;       rst = 0;
+      $finish;
    end
 
 endmodule