m4v8_1.vhd

1、正常的计时功能：即具有二十四小时计时功能 2、正常的显示功能 3、正常的调时功能 4、闹钟定时功能 5、整点报时功能

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;
entity m4v8_1 is
   port(a,b,c,d,e,f,g,h:in std_logic_vector(3 downto 0);
        sel:in std_logic_vector(2 downto 0);
        y:out std_logic_vector(3 downto 0));
end m4v8_1;
architecture arch of m4v8_1 is
begin
    process(a,b,c,d,e,f,g,h,sel)
    begin
         case sel is
             when "000"=>y<=a;
             when "001"=>y<=b;
             when "010"=>y<=c;
             when "011"=>y<=d;
             when "101"=>y<=f;
             when "100"=>y<=e;
             when "110"=>y<=g;
             when "111"=>y<=h;
             when others=>y<="0000";
         end case;
    end process;
end arch;