code for traffic light controller

`timescale 1ns / 1ps
//////////////////////////////////////////////////////////////////////////////////
// Company:
// Engineer:
//
// Create Date:    09:48:37 12/17/2014
// Design Name:
// Module Name:    traffic
// Project Name:
// Target Devices:
// Tool versions:
// Description:
//
// Dependencies:
//
// Revision:
// Revision 0.01 - File Created
// Additional Comments:
//
//////////////////////////////////////////////////////////////////////////////////


// code foe traffic light controller
module traffic_lights;
reg clock, red, amber, green;
parameter on = 1, off = 0, red_tics = 30, amber_tics = 3, green_tics = 20;
initial red = off;
initial amber = off;
initial green = off;

always begin // sequence to control the lights.
red = on; // turn red light on
light(red, red_tics); // and wait.
green = on; // turn green light on
light(green, green_tics); // and wait.
amber = on; // turn amber light on
light(amber, amber_tics); // and wait.
end


task light;
output color;
input [31:0] tics;
begin
repeat (tics) @ (posedge clock);
color = off; // turn light off.
end
endtask


always begin // waveform for the clock.
#10 clock = 0;
#10 clock = 1;
end endmodule

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