24计数counter24.txt

具有多种功能的电子钟：闹钟

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;
entity counter24 is
port(cp   :in  std_logic;
     bin  :out std_logic_vector(5 downto 0);
     s    :in  std_logic;
     clr  :in  std_logic;
     ec   :in  std_logic;
     cy24 :out std_logic);
end counter24;
architecture a of counter24 is
     signal q : std_logic_vector(4 downto 0);
     signal rst,dly : std_logic;
begin
    process(cp,rst)
     begin
          if rst='1'then
               q<="00000";
          else if cp'event and cp='1' then
              dly<=q(4);
              if ec='1' then
                    q<=q+'1';
               end if;
              end if;
          end if;
      end process;
      cy24<=not q(4) and dly;
      rst<='1'when q=24 or clr='1' else
           '0';
      bin<=('0'&q)when s='1' else
           "000000";
end a;