always @(posedge clk)
    begin
        if(refresh_counter == 20'b1111_1111_1111_1111_1111)
            refresh_counter <= 20'b0;
        else
            refresh_counter <= refresh_counter + 1;
    end
    assign turn = refresh_counter[19:18];
    always@(*) begin
        case(turn)
            2'b00:begin
                DIGIT <= 4'b0111;
                led_BCD <= min_display / 10;
            end
            2'b01:begin
                DIGIT <= 4'b1011;
                led_BCD <= min_display % 10;
            end
            2'b10:begin
                DIGIT <= 4'b1101;
                led_BCD <= sec_display / 10;
            end
            2'b11:begin
                DIGIT <= 4'b1110;
                led_BCD <= sec_display % 10;
            end
            default: begin end
        endcase
    end
    always @(*)
    begin
        case(led_BCD)
        4'b0000: DISPLAY <= 7'b0000001; // "0"
        4'b0001: DISPLAY <= 7'b1001111; // "1"
        4'b0010: DISPLAY <= 7'b0010010; // "2"
        4'b0011: DISPLAY <= 7'b0000110; // "3"
        4'b0100: DISPLAY <= 7'b1001100; // "4"
        4'b0101: DISPLAY <= 7'b0100100; // "5"
        4'b0110: DISPLAY <= 7'b0100000; // "6"
        4'b0111: DISPLAY <= 7'b0001111; // "7"
        4'b1000: DISPLAY <= 7'b0000000; // "8"
        4'b1001: DISPLAY <= 7'b0000100; // "9"
        default: DISPLAY <= 7'b0000100; // "9"
        endcase
    end