stopwatch.vhd.bak

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
entity stopwatch is port( hex0 :out std_logic_vector(0 to 6);
                    hex1 :out std_logic_vector(0 to 6);
                    hex2 :out std_logic_vector(0 to 6);
                    hex3 :out std_logic_vector(0 to 6);
                    SW: in std_logic_vector(0 to 9);
                    key: in std_logic_vector(0 to 3);
                    clock_50 : std_logic
                    );
              function segment (s: integer:=0) --Ease output to 7-segment
                return std_logic_vector is
              begin
                case s is
                  when 0 => return "0000001";
                  when 1 => return "1001111";
                  when 2 => return "0010010";
                  when 3 => return "0000110";
                  when 4 => return "1001100";
                  when 5 => return "0100100";
                  when 6 => return "0100000";
                  when 7 => return "0001101";
                  when 8 => return "0000000";
                  when 9 => return "0000100";
                  when others => return "1111111";
                end case;
              end segment;
end;

architecture counter of stopwatch is
  signal count : integer := 1;
  signal clk : std_logic :='0';
begin --divide clock from 50Mhz to 10hz

  process(clock_50)

  begin
    if(clock_50'event and clock_50='1') then
      count <= count+1;
      if(count = 2500000) then
        clk <= not clk;
        count <= 1;
      end if;
    end if;
  end process;

  process(clk)--period of clk is 0.1 second (10Hz)
    type timee is array(0 to 3) of integer;
    variable zetime: timee:=(0,0,0,0) ;
    variable flag: std_logic;

  begin
--Make key push button behave like switch
    if(key(0)'event and key(0)'last_value='0') then
      flag:=not flag;
    end if;
    if(clk'event and clk='1' and flag='1' ) then --here the main shit happens
      zetime(0):= zetime(0)+1;
      if (zetime(0)=10) then
        zetime(0):=0;
        zetime(1):= zetime(1)+1;
        if (zetime(1)=10) then
          zetime(1):=0;
          zetime(2):= zetime(2)+1;
          if (zetime(2)=6) then
            zetime(2):=0;
            zetime(3):= zetime(3)+1;
          end if;
        end if;
      end if;
    end if;
    if(key(1)='0') then --  clean 7-segment display
      zetime:=(0,0,0,0);
    end if;

    hex0<=segment(zetime(0)); --call to function
    hex1<=segment(zetime(1));
    hex2<=segment(zetime(2));
    hex3<=segment(zetime(3));
  end process;
end;