demux4.vhd

在quartus开发环境下

library ieee;
use ieee.std_logic_1164.all;
entity demux4 is
port(din:in std_logic;
     a:in std_logic_vector(1 downto 0);
     y0,y1,y2,y3:out std_logic);
end;
architecture one of demux4 is
begin
process(din,a)
begin
y0<='0';y1<='0';y2<='0';y3<='0';
case a is
when "00"=>y0<=din;
when "01"=>y1<=din;
when "10"=>y2<=din;
when "11"=>y3<=din;
when others=>null;
end case;
end process;
end;