问如何在Verilog中添加“红黄”灯的状态

EN

`timescale 1ns / 1ps
module Traffic
(
  input       reset,
  input       clk,
  input       NS_VEHICLE_DETECT,
  input       EW_VEHICLE_DETECT,
  output wire NS_RED,
  output wire NS_YELLOW,
  output wire NS_GREEN,
  output wire EW_RED,
  output wire EW_YELLOW,
  output wire EW_GREEN
);

reg [5:0] lights; //  {NS_RED, NS_YELLOW, NS_GREEN, EW_RED, EW_YELLOW, EW_GREEN}
reg [4:0] nsCounter;
reg [3:0] ewCounter;
reg [1:0] yellowCounter;


assign {NS_RED, NS_YELLOW, NS_GREEN, EW_RED, EW_YELLOW, EW_GREEN} = lights;


always @(posedge clk)
   if (reset)
      lights <= 6'b001100;
   else
     if (nsCounter == 31 & EW_VEHICLE_DETECT & NS_GREEN)
       lights <= 6'b010100;
     else
       if (ewCounter == 15 & EW_GREEN) 
         lights <= 6'b100010;
       else
         if (yellowCounter == 3 & NS_YELLOW)
           lights <= 6'b100001;
         else
           if (yellowCounter == 3 & EW_YELLOW) 
             lights <= 6'b001100;
//------------------------------------

always @(negedge clk)
  if (reset)
    begin
      nsCounter     <= 5'h0;
      ewCounter     <= 4'h0;
      yellowCounter <= 2'h0;
    end
  else
    begin
      nsCounter     <= nsCounter     + 1'b1;
      ewCounter     <= ewCounter     + 1'b1; 
      yellowCounter <= yellowCounter + 1'b1;
    end
//------------------------------------

endmodule
//====================================