Design a State machine for Traffic Control at a Four point Junction?

Answer 1

/************************************************************** * This is main module for state machine of TrafficLight **************************************************************/ module TrafficLight(state, RedLight, GreenLight, YellowLight, clk, reset, malfunction, ready); input clk, reset, ready; //ready is high when maintenance of TrafficLight finished input malfunction; //system input malfunction when error occured output [1:0] state; output RedLight,GreenLight,YellowLight; //active-high output for Lights reg [1:0] state; //register to store current state reg RedLight,GreenLight,YellowLight; //define parameter or name of each state parameter redstate = 2'b00; parameter greenstate = 2'b01; parameter yellowstate = 2'b10; parameter maintenance = 2'b11; always@ (posedge reset or posedge clk) begin RedLight = (!state[1] & !state[0]); GreenLight = (!state[1] & state[0]); YellowLight = (state[1] & !state[0]); if(reset) begin state = redstate; //default state is RedLight on end else case(state) redstate: begin if(malfunction) state = maintenance; else state = greenstate; end greenstate: begin if(malfunction) state = maintenance; else state = yellowstate; end yellowstate: begin if(malfunction) state = maintenance; else state = redstate; end maintenance: begin if(ready) state = redstate; else state = maintenance; end endcase end endmodule /************************************************************** * This module is for testing and display outputs. **************************************************************/ module test_module; // declare test module reg clk, reset, malfunction, ready; wire [1:0] state; wire RedLight, GreenLight, YellowLight; parameter clockDelay = 50; TrafficLight myTrafficLight(state, RedLight, GreenLight, YellowLight, clk, reset, malfunction, ready); always begin #(clockDelay/2) clk = 0; #(clockDelay/2) clk = 1; end initial begin //$dumpfile("Trafficlight.dump"); //$dumpvars; $monitor ("stat= %b, RedLight = %b, Green = %b, YellowLight = %b",state, RedLight, GreenLight, YellowLight); $shm_open("db1.shm"); // Open a directory to store waveforms $shm_probe(state, RedLight, GreenLight, YellowLight, reset, malfunction, ready); // Specify any signals you want waveforms for #(clockDelay) reset = 1'b1; #(clockDelay) reset = 1'b0; #(clockDelay) malfunction = 1'b1; #(clockDelay) reset = 1'b0; #(clockDelay) malfunction = 1'b0; #(clockDelay) #(clockDelay) #(clockDelay) ready = 1'b1; #(clockDelay) ready = 1'b0; #(clockDelay) #(clockDelay) #(clockDelay) #(clockDelay) reset = 1'b1; #(clockDelay) reset = 1'b0; #(clockDelay) #(clockDelay) malfunction = 1'b1; #(clockDelay) malfunction = 1'b0; #(clockDelay) #(clockDelay) #(clockDelay) ready = 1'b1; #(clockDelay) ready = 1'b0; #(80*clockDelay) $finish; end endmodule