traffic_light_controller2.v

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//***************************************************
// File Name: traffic_light_controller.v
//      Date: October7,2008
//    author: yilong.you
//            [e-mail]   
//**************************************************/

module traffic_light_controller2(clk,reset,light_color);
 input clk,reset;
 output[1:0] light_color; 

 reg[1:0] light_color,state;
 reg[5:0]count;
 
 parameter S0=2'd0,green=2'd1,yellow=2'd2,red=2'd3;
 
 initial state=S0;
 always@(posedge clk or  posedge reset)begin
       if(reset)begin
          state<=S0;
          count<=0;
       end
       else        	  
       	  case(state)
       	  	     S0: state<=green;
              green: begin
              	         count<=count+1;
                         if(count==24)
                            state<=yellow;             
                     end
          
              yellow:begin
              	         count<=count+1;
              	         if(count==26)
                           state<=red;              
                     end
          
                 red: begin
               	         count<=count+1;
                         if(count==41)
                           state<=green;              
                    end 
            default: count<=count+1;
       endcase    
 end
 always@(negedge clk) light_color<=state;
endmodule