selects.vhd

米字型数码管的编码方法。自动循环显示至少四个以上单词。

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;

entity selects is
port(clk : in std_logic;
     X1,X2,X3,X4 : in std_logic_vector(15 downto 0);
     sele : out std_logic_vector(3 downto 0);
     outp : out std_logic_vector(15 downto 0));
end entity selects;

architecture art of selects is
  signal data : std_logic_vector(3 downto 0);
  signal cont : std_logic_vector(3 downto 0);
  signal num : std_logic_vector(1 downto 0);
  begin
  process (clk) is
    begin
    if (clk'event and clk = '1') then
        if data = "0000" then
           data <= "1110";
        else
           data <= data(2 downto 0) & data(3);
           sele <= data;
       end if;
       if cont = "0000" then
          cont <= "1111";
          if num = "11" then
             num <= "00";
             outp <= X4;
          else
          case num is
              when "00" => outp <= X1;
              when "01" => outp <= X2;
              when "10" => outp <= X3;
              when "11" => outp <= X4;
              when others => null;
          end case;
          num <= num + 1;
          end if;
       else
           cont <= cont - 1;
       end if;
    end if;
  end process;
end architecture art;