//***************************************************// File Name: traffic_light_controller.v//      Date: September 29,2008//    author: yilong.you//            yilong.you@stu.xjtu.edu.cn   //**************************************************/module traffic_light_controller(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 begin       	  if(count===0)            state<=green;                   if(count==24)begin            state<=yellow;            count<=count+1;          end                    else if(count==26)begin            state<=red;            count<=count+1;          end                    else if(count==41)begin            state<=green;            count<=0;          end           else count<=count+1;       end end always@(negedge clk) light_color<=state;endmodule