scan.vhd

VHDL的数字钟

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
entity scan is
   port(hou1,hou0,min1,min0,sec1,sec0:in std_logic_vector(3 downto 0);
        nia1,nia0,yue1,yue0,ri1,ri0:in std_logic_vector(3 downto 0);
        pmi1,pmi0,pse1,pse0,pus1,pus0:in std_logic_vector(3 downto 0);
        nho1,nho0,nmi1,nmi0:in std_logic_vector(3 downto 0);
        clk1khz, bm, cho:in std_logic;
        num:out std_logic_vector(3 downto 0);
        sel:out std_logic_vector(2 downto 0));
end scan;
architecture one of scan is  
signal count:std_logic_vector(2 downto 0);
signal bmi,choi:std_logic_vector(1 downto 0);
signal ms,chos: integer range 0 to 3; 
 begin
  process(clk1khz,bm,cho,ms,chos)
   begin
    if ms<4 then
     if rising_edge(bm) then ms<=ms+1;
     end if;
    else ms<=0;
    end if;
     case ms is
      when 0=>
       if chos<4 then
       if rising_edge(cho) then chos<=chos+1;
       end if;
       else chos<=0;
       end if;
       if rising_edge(clk1khz) then
       case chos is
        when 0=>
        case count is
         when "000"=>num<=sec0;sel<="000";count<="001";
         when "001"=>num<=sec1;sel<="001";count<="010";
         when "010"=>num<=min0;sel<="011";count<="011";
         when "011"=>num<=min1;sel<="100";count<="100";
         when "100"=>num<=hou0;sel<="110";count<="101";
         when "101"=>num<=hou1;sel<="111";count<="000";
         when others=>null;
        end case;
        when 1=>
        case count is
         when "000"=>num<="1111";sel<="000";count<="001";
         when "001"=>num<="1111";sel<="001";count<="010";
         when "010"=>num<="1111";sel<="011";count<="011";
         when "011"=>num<="1111";sel<="100";count<="100";
         when "100"=>num<=hou0;sel<="110";count<="101";
         when "101"=>num<=hou1;sel<="111";count<="000";
         when others=>null;
        end case;
        when 2=>
        case count is
         when "000"=>num<="1111";sel<="000";count<="001";
         when "001"=>num<="1111";sel<="001";count<="010";
         when "010"=>num<=min0;sel<="011";count<="011";
         when "011"=>num<=min1;sel<="100";count<="100";
         when "100"=>num<=hou0;sel<="110";count<="101";
         when "101"=>num<=hou1;sel<="111";count<="000";
         when others=>null;
        end case;
        when 3=>
        case count is
         when "000"=>num<=sec0;sel<="000";count<="001";
         when "001"=>num<=sec1;sel<="001";count<="010";
         when "010"=>num<=min0;sel<="011";count<="011";
         when "011"=>num<=min1;sel<="100";count<="100";
         when "100"=>num<=hou0;sel<="110";count<="101";
         when "101"=>num<=hou1;sel<="111";count<="000";
         when others=>null;
        end case;
        when others=>null;
       end case;
      end if;
      when 1=>
       if chos<4 then
       if rising_edge(cho) then chos<=chos+1;
       end if;
       else chos<=0;
       end if;
       if rising_edge(clk1khz) then
       case chos is
        when 0=>
        case count is
         when "000"=>num<=ri0;sel<="000";count<="001";
         when "001"=>num<=ri1;sel<="001";count<="010";
         when "010"=>num<=yue0;sel<="011";count<="011";
         when "011"=>num<=yue1;sel<="100";count<="100";
         when "100"=>num<=nia0;sel<="110";count<="101";
         when "101"=>num<=nia1;sel<="111";count<="000";
         when others=>null;
        end case;
        when 1=>
        case count is
         when "000"=>num<="1111";sel<="000";count<="001";
         when "001"=>num<="1111";sel<="001";count<="010";
         when "010"=>num<="1111";sel<="011";count<="011";
         when "011"=>num<="1111";sel<="100";count<="100";
         when "100"=>num<=nia0;sel<="110";count<="101";
         when "101"=>num<=nia1;sel<="111";count<="000";
         when others=>null;
        end case;
        when 2=>
        case count is
         when "000"=>num<="1111";sel<="000";count<="001";
         when "001"=>num<="1111";sel<="001";count<="010";
         when "010"=>num<=yue0;sel<="011";count<="011";
         when "011"=>num<=yue1;sel<="100";count<="100";
         when "100"=>num<=nia0;sel<="110";count<="101";
         when "101"=>num<=nia1;sel<="111";count<="000";
         when others=>null;
        end case;
        when 3=>
        case count is
         when "000"=>num<=ri0;sel<="000";count<="001";
         when "001"=>num<=ri1;sel<="001";count<="010";
         when "010"=>num<=yue0;sel<="011";count<="011";
         when "011"=>num<=yue1;sel<="100";count<="100";
         when "100"=>num<=nia0;sel<="110";count<="101";
         when "101"=>num<=nia1;sel<="111";count<="000";
         when others=>null;
        end case;
        when others=>null;
       end case;
      end if;
      when 2=>
      if rising_edge(clk1khz) then
       case count is
        when "000"=>num<=pus0;sel<="000";count<="001";
        when "001"=>num<=pus1;sel<="001";count<="010";
        when "010"=>num<=pse0;sel<="011";count<="011";
        when "011"=>num<=pse1;sel<="100";count<="100";
        when "100"=>num<=pmi0;sel<="110";count<="101";
        when "101"=>num<=pmi1;sel<="111";count<="000";
        when others=>null;
       end case;
      end if;
      when 3=>
       if rising_edge(clk1khz) then
       case count is
        when "000"=>num<="1111";sel<="000";count<="001";
        when "001"=>num<="1111";sel<="001";count<="010";
        when "010"=>num<=nmi0;sel<="011";count<="011";
        when "011"=>num<=nmi1;sel<="100";count<="100";
        when "100"=>num<=nho0;sel<="110";count<="101";
        when "101"=>num<=nho1;sel<="111";count<="000";
        when others=>null;
       end case;
       end if;
      when others=>null;
     end case;
end process;
end;