fpga-lab-2/HDL/dec.sv

module dec
  #(m = 32)
    (
     //clock and reset
     input logic         clk, clrn,
     //control slave
     input logic         ctl_wr, ctl_rd,
     input logic         ctl_addr,
     input logic [31:0]  ctl_wrdata,
     output logic [31:0] ctl_rddata,
     //memory slave
     input logic         ram_wr,
     input logic [3:0]   ram_addr,
     input logic [31:0]  ram_wrdata,
     //external ports
     input logic         train,
     output logic        red, yellow, green
     );

    typedef enum         logic [1:0] {RED, YELLOW, BLINK, GREEN} FSMStates;

    logic                run;
    logic [1:0]          divider;
    logic [1:0]          state;
    logic [31:0]         greenSaved;
    logic [31:0]         greenCount;    

    logic [m-1:0]        divisor;
    logic [1:0]          contr;
    logic [2:0]          colors;
    logic [m-1:0]        cntdiv;
    logic                enacnt;

    //control slave logic
    always_ff @ (posedge clk or negedge clrn) begin
        if (!clrn) begin
            run <= 0;
            divider <= 0;
        end else begin
            if (ctl_wr) begin
                case (ctl_addr)
                  1'b0: run <= ctl_wrdata[0];
                  1'b1: divider <= ctl_wrdata[1:0];
                endcase
            end
        end
    end

    always_comb begin
        case (ctl_addr)
          1'b0: ctl_rddata = {31'b0,run};
          1'b1: ctl_rddata = {30'b0,divider};
          default: ctl_rddata = 'bx;
        endcase
    end

    //semaphore logic
    always_ff @ (posedge clk or negedge clrn) begin
        if (!clrn)
          cntdiv <= 0;
        else begin
            if (train | ~run)
              cntdiv<=0;
            else begin
                if (enacnt) cntdiv<=0;
                else cntdiv<=cntdiv+1;
            end
        end
    end

    // we don't enable counters, if color is green
    always_comb begin
        enacnt = ((cntdiv == divisor) && !(colors == 3'b001));
    end

    always_ff @ (posedge clk or negedge clrn) begin
        if (!clrn) begin
            colors <= 3'b001;
            state <= GREEN;
            greenCount <= 32'd0;
        end else begin
            if (~run) begin
                colors <= 3'b001;
                state <= GREEN;
            end
            if (train) begin
                colors <= 3'b100;
                state <= RED;
                greenSaved <= divisor;
                greenCount <= divisor;
            end else begin
                case (state)
                  RED: begin
                      colors <= 3'b100;
                      if (enacnt) begin
                          state <= YELLOW;
                          greenSaved <= divisor;
                      end
                  end
                  YELLOW: begin
                      colors <= 3'b010;
                      if (enacnt) begin
                          state <= BLINK;
                      end
                  end
                  BLINK: begin
                      if (enacnt) begin
                          state <= GREEN;
                      end
                      if (greenSaved[0] == 0) begin
                          colors <= 3'b011;
                      end else begin
                          greenCount <= greenCount - 1'b1;
                          if (greenCount == 32'd0) begin
                              colors[1] <= ~colors[1];
                              greenCount <= greenSaved;
                          end
                      end
                  end
                  GREEN: begin
                      colors <= 3'b001;
                  end
                  default: colors <= 3'b100;
                endcase
            end
        end
    end
    assign contr = state;
    // always_comb begin
    //     case (state)
    //       2'b00: contr = 2'b00;
    //       2'b01: contr = 2'b01;
    //       2'b10: contr = 2'b10;
    //       2'b11: contr = 2'b11;
    //       default : contr = 2'b00;
    //     endcase
    // end

    assign red = colors[2];
    assign yellow = colors[1];
    assign green = colors[0];

    periodram   b2v_inst3
      (
       .clock(clk),
       .data (ram_wrdata),
       .wraddress (ram_addr),
       .wren (ram_wr),
       .rdaddress({divider,contr}),
       .q(divisor)
       );

endmodule