keyin.vhd

（1）、自动售货机可以出售4种货物

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

entity keyin is
   port(clk1   :in std_logic;
        col    :in std_logic_vector(3 downto 0);
        row    :out std_logic_vector(3 downto 0);
        bcdmin :out std_logic_vector(3 downto 0));
   end;

architecture a of keyin is
     signal line:std_logic_vector( 3 downto 0);
begin
p1:
    process(clk1)
    begin
         if(line="0000")then line<="1000";
         elsif(clk1'event and clk1='1')then
            line (3 downto 0)<= line (2 downto 0)&line(3);
         end if;
    end process p1;
    row(3)<=line(3);
    row(2)<=line(2);
    row(1)<=line(1);
    row(0)<=line(0);
p2:
    process
    begin
       if(line="0000"and col="10000") then bcdmin<="0001";
       elsif(line="1000" and col="0100")then
           bcdmin<="0010";
       elsif(line="1000" and col="0010")then
           bcdmin<="0011";
       elsif(line="0100" and col="1000")then
           bcdmin<="0101";
       elsif(line="0100" and col="0100")then
           bcdmin<="0110";
       elsif(line="0100" and col="0010")then
           bcdmin<="0111";
       else bcdmin<="0000";
      end if;
   end process p2;
end;