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

entity source is

port(clk:in std_logic:='0';
     dataout:out std_logic
    );
end;
architecture a of source is
signal data:std_logic_vector(0 to 15);
begin
data<="1111001110001100";    --發(fā)送的16位數(shù)據(jù)
process(clk)
variable m:integer range 0 to 15;
variable n:integer range 0 to 15;
begin
 if(clk'event and clk='1') then  
     n:=m mod 16 ;
     dataout<=data(n);
    m:=m+1;
 end if;
end process;
end ;