library ieee;   --1位乘法器
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
use ieee.std_logic_arith.all;
entity multi_1 is        
port(m1_x:in std_logic;
     m1_y:in std_logic_vector(7 downto 0);
     m1_out:out std_logic_vector(7 downto 0));
end multi_1;
architecture arc_multi_1 of multi_1 is 
begin 
  process(m1_x,m1_y)
  begin
   if m1_x='1' then m1_out<=m1_y;
   else m1_out<="00000000";
   end if;
  end process;
end arc_multi_1;