timer.txt

VHDL语言设计的数字钟 具有时分秒三段显示

---------------------------------------------------------------------
-- Design unit: timer(display) (Entity and Architectures)
-- File name  : timer.vhd
-- Description: 24 hours timer
-- Limitations: None
-- System     : VHDL'93
-- Author     : Fan Bishuang
-- Email      : [e-mail]
-- Revision   : Version 1.0 16/5/05
---------------------------------------------------------------------
library IEEE;
use IEEE.std_logic_1164.all;
entity timer is
  port(clk : in  std_logic; -- System clock input port(250KHz).
       L   : out std_logic_vector(2 downto 0); -- 8 seven-segment displays selection ports.
       dled: out std_logic_vector(7 downto 0)); -- Digits display ports.
end timer;
architecture display of timer is
begin
  process (clk)
    variable cnt: integer range 0 to 7; -- 8 seven-segment displays seletion counter.
    variable ct:integer range 0 to 250000 ; -- 1 second generator counter.
    variable hourH: integer range 0 to 2; 
    variable minuteH,secondH: integer range 0 to 6;
    variable hourL,minuteL,secondL: integer range 0 to 10;
  begin
    if clk'event and clk = '1' then
      cnt:=cnt+1;
      ct:=ct+1;
      if ct=250000 then -- 1 second 
        ct:=0;
        secondL:=secondL+1;
      end if;
      if secondL=10 then -- 10 seconds
        secondL:=0;
        secondH:=secondH+1;
      end if;
      if secondH=6 then -- 60 seconds(1 minute)
        secondH:=0;
        minuteL:=minuteL+1;
      end if; 
      if minuteL=10 then -- 10 minutes
        minuteL:=0;
        minuteH:=minuteH+1;
      end if;
      if minuteH=6 then -- 60 minutes(1 hour)
        minuteH:=0;
        hourL:=hourL+1;
      end if;  
      if hourL=10 then -- 10 hours
        hourL:=0;
        hourH:=hourH+1;
      end if;   
      if hourH=2 and hourL =4 then -- 24 hours 
        hourH:=0;
        hourL:=0;
      end if;   
      case cnt is -- To display the time.
        when 0 => L<="000"; -- Enable the leftmost display.
          case hourH is
            when 0 => dled<=X"FC";--0
            when 1 => dled<=X"60";--1
            when 2 => dled<=X"DA";--2
            when others => null;
          end case;
        when 1 => L<="001"; -- Enable the second display.
          case hourL is
            when 0 => dled<=X"FC";--0
            when 1 => dled<=X"60";--1
            when 2 => dled<=X"DA";--2
            when 3 => dled<=X"F2";--3
            when 4 => dled<=X"66";--4
            when 5 => dled<=X"B6";--5
            when 6 => dled<=X"BE";--6
            when 7 => dled<=X"E0";--7
            when 8 => dled<=X"FE";--8
            when 9 => dled<=X"F6";--9
            when others => null;
          end case;
        when 2 => L<="010"; -- Enable the third display.
          dled<=X"00";  	-- Blanked.
        when 3 => L<="011"; -- Enable the fourth display.
          case minuteH is
            when 0 => dled<=X"FC";--0
            when 1 => dled<=X"60";--1
            when 2 => dled<=X"DA";--2
            when 3 => dled<=X"F2";--3
            when 4 => dled<=X"66";--4
            when 5 => dled<=X"B6";--5
            when others => null;
          end case;
        when 4 => L<="100"; -- Enable the fifth display.
          case minuteL is
            when 0 => dled<=X"FC";--0
            when 1 => dled<=X"60";--1
            when 2 => dled<=X"DA";--2
            when 3 => dled<=X"F2";--3
            when 4 => dled<=X"66";--4
            when 5 => dled<=X"B6";--5
            when 6 => dled<=X"BE";--6
            when 7 => dled<=X"E0";--7
            when 8 => dled<=X"FE";--8
            when 9 => dled<=X"F6";--9
            when others => null;
          end case;
        when 5 => L<="101"; -- Enable the sixth display.
          dled<=X"00"; 		-- Blanked.
        when 6 => L<="110"; -- Enable the seventh display.
          case secondH is
            when 0 => dled<=X"FC";--0
            when 1 => dled<=X"60";--1
            when 2 => dled<=X"DA";--2
            when 3 => dled<=X"F2";--3
            when 4 => dled<=X"66";--4
            when 5 => dled<=X"B6";--5
            when others => null;
          end case;
        when 7 => L<="111"; -- Enable the rightmost display 
          case secondL is
            when 0 => dled<=X"FC";--0
            when 1 => dled<=X"60";--1
            when 2 => dled<=X"DA";--2
            when 3 => dled<=X"F2";--3
            when 4 => dled<=X"66";--4
            when 5 => dled<=X"B6";--5
            when 6 => dled<=X"BE";--6
            when 7 => dled<=X"E0";--7
            when 8 => dled<=X"FE";--8
            when 9 => dled<=X"F6";--9
            when others => null;
          end case;
      end case;
    end if;
  end process;
end display;