-- infinite loop example 

library ieee;
use ieee.std_logic_1164.all;

entity infinite_loop is
end infinite_loop;

architecture behavioral of infinite_loop  is
   -- For synthesizable code, initialization of signal values 
   -- should not be done in the declaration section since the
   -- synthesis tool ignores initialization of values in the 
   -- declaration section.
   signal a : std_ulogic := '0' ;
   signal b : std_ulogic := '1' ;
   signal y : std_ulogic := '1' ;
   signal z : std_ulogic := '0' ;

begin

   p1: process(a,z)
   begin
     y <= a or z ;
   end process p1;

   p2: process(b,y)
   begin
     z <= b and y ;
   end process p2;

end behavioral;