library IEEE;
use ieee.std_logic_1164.all;
use IEEE.numeric_std.all;
use ieee.std_logic_unsigned.all;

Entity SegmentDriver is
    port(
		clk_480: in std_logic;
		clk_counter: in std_logic;
    	StartButton: in std_logic;
		reset: in std_logic;
    	inclk  : IN  std_logic;
		cathode: out std_logic_vector (7 downto 0);
		anode: out std_logic_vector (3 downto 0)
        );
End SegmentDriver;

architecture behavioral of SegmentDriver is
    signal PS,NS: std_logic_vector(1 downto 0):= "00";
    signal a,b,x,y: integer:=0;
    signal ss1, ss2, en : std_logic:= '0';
begin
    process(inclk)
        begin
        if (rising_edge(inclk)) then
        PS <= NS;
        end if;
    end process;

    adding: process (StartButton,clk_counter,PS, NS, ss1,ss2)
        begin
            if reset = '1'then
                a<=0;
                b<=0;
                x<=0;
                y<=0;
            else
            if(rising_edge(clk_counter))then
                if StartButton ='1' then
                    ss1 <= '1';
                elsif StartButton = '0' then
                    ss1 <= '0';
                end if;
                ss2<= ss1;
                if ss2 = '0' and ss1 = '1' then
                    en <= not en;
                    end if;
                case (PS) is
                    when "11" => -- when the clock is already running
                        if en = '1' then
                            NS <= "11";
                            y <= y + 1; --code to have the stopwatch actually count
                            if y = 9 then
                                x <= x + 1;
                                y <= 0;
                                if x = 9 then
                                    b <= b + 1;
                                    x <= 0;
                                    if b = 9 then
                                        a <= a + 1;
                                        b <= 0;
                                        if a = 9 then --rolls over when it gets to 99.99
                                            a <= 0;
                                            b <= 0;
                                            x <= 0;
                                            y <= 0;
                                         end if;
                                    end if;
                                end if;
                            end if;
                        elsif en = '0' then
                            NS <= "00";
                        end if;
                    when "00" => --when the stopwatch is stopped
                        if en = '0' then
                            NS <= "00";
                            a <= a;
                            b <= b;
                            x <= x;
                            y <= y;
                        elsif en = '1' then
                            NS <= "11";
                        end if;
                    when others => --should never happen
                        NS <= "00";
                        a <= 0;
                        b <= 0;
                        x <= 0;
                        y <= 0;
                end case;
            end if;
        end if;
    end process;

    led : process (clk_480) --tells leds when to turn on
        variable digit1, digit2: unsigned (1 downto 0):="00";
    begin
        if (rising_edge(clk_480)) then
            case(digit1) is
                when "00" => anode <= "0111";
                when "01" => anode <= "1011";
                when "10" => anode <= "1101";
                when "11" => anode <= "1110";
                when others =>
            end case;
            case (digit2) is
                 when "00" =>
                    case (a) is
                        when 0 => cathode <= "00000011";
                        when 1 => cathode <= "10011111";
                        when 2 => cathode <= "00100101";
                        when 3 => cathode <= "00001101";
                        when 4 => cathode <= "10011001";
                        when 5 => cathode <= "01001001";
                        when 6 => cathode <= "01000001";
                        when 7 => cathode <= "00011111";
                        when 8 => cathode <= "00000001";
                        when 9 => cathode <= "00011001";
                        when others => cathode <= "00000000";
                    end case;

                when "01" =>
                    case (b) is
                        when 0 => cathode <= "00000010";
                        when 1 => cathode <= "10011110";
                        when 2 => cathode <= "00100100";
                        when 3 => cathode <= "00001100";
                        when 4 => cathode <= "10011000";
                        when 5 => cathode <= "01001000";
                        when 6 => cathode <= "01000000";
                        when 7 => cathode <= "00011110";
                        when 8 => cathode <= "00000000";
                        when 9 => cathode <= "00011000";
                        when others => cathode <= "00000000";
                    end case;

                when "10" =>
                    case (x) is
                        when 0 => cathode <= "00000011";
                        when 1 => cathode <= "10011111";
                        when 2 => cathode <= "00100101";
                        when 3 => cathode <= "00001101";
                        when 4 => cathode <= "10011001";
                        when 5 => cathode <= "01001001";
                        when 6 => cathode <= "01000001";
                        when 7 => cathode <= "00011111";
                        when 8 => cathode <= "00000001";
                        when 9 => cathode <= "00011001";
                        when others => cathode <= "00000000";
                    end case;
                when "11" =>
                    case (y) is
                        when 0 => cathode <= "00000011";
                        when 1 => cathode <= "10011111";
                        when 2 => cathode <= "00100101";
                        when 3 => cathode <= "00001101";
                        when 4 => cathode <= "10011001";
                        when 5 => cathode <= "01001001";
                        when 6 => cathode <= "01000001";
                        when 7 => cathode <= "00011111";
                        when 8 => cathode <= "00000001";
                        when 9 => cathode <= "00011001";
                        when others => cathode <= "00000000";
                    end case;
                when others=>
             -- fixes simulation bug --
            end case;
            digit1 := digit1 + 1;
            digit2 := digit2 + 1;
        end if;
    end process;
end Behavioral;