| module led_controller( | |
| input wire clk, reset, pedestrian_button, car_sensor, | |
| output reg [2:0] lights | |
| ); | |
| localparam RED = 3'b001, YELLOW = 3'b010, GREEN = 3'b100; | |
| localparam WAIT = 2'b00, GO = 2'b01, WARN = 2'b10, STOP = 2'b11; | |
| reg [1:0] state, next_state; | |
| reg [31:0] count; | |
| initial begin | |
| state = WAIT; | |
| count = 0; | |
| end | |
| always @(posedge clk or posedge reset) begin | |
| if (reset) begin | |
| state <= WAIT; | |
| count <= 0; | |
| end else begin | |
| state <= next_state; | |
| if (count == 10) begin | |
| count <= 0; | |
| end else begin | |
| count <= count + 1; | |
| end | |
| end | |
| end | |
| always @* begin | |
| case (state) | |
| WAIT: begin | |
| if (car_sensor) begin | |
| lights = RED; | |
| next_state = GO; | |
| end else begin | |
| lights = YELLOW; | |
| next_state = WARN; | |
| end | |
| end | |
| GO: begin | |
| if (count < 6) begin | |
| lights = GREEN; | |
| next_state = GO; | |
| end else begin | |
| lights = YELLOW; | |
| next_state = WARN; | |
| end | |
| end | |
| WARN: begin | |
| if (count < 2) begin | |
| lights = YELLOW; | |
| next_state = WARN; | |
| end else if (pedestrian_button) begin | |
| lights = RED; | |
| next_state = STOP; | |
| end else begin | |
| lights = RED; | |
| next_state = GO; | |
| end | |
| end | |
| STOP: begin | |
| if (count < 4) begin | |
| lights = RED; | |
| next_state = STOP; | |
| end else begin | |
| lights = GREEN; | |
| next_state = GO; | |
| end | |
| end | |
| endcase | |
| end | |
| endmodule | |