JOHNSON COUNTER (4-Bit)- (Behavioral)

library ieee;

use ieee.std_logic_1164.all;

Entity J_COUNTER is

port(clr,clk,pr:in std_logic;Q:inout std_logic_vector(0 to 3));

end J_COUNTER;

Architecture behavioral of J_COUNTER is

begin

process( clr,clk,pr)

begin

 if (pr ='0') then Q<="1111";

elsif (clr ='0') then Q<="0000";

elsif clk='1' and clk'event then

Q(0)<=not Q(3);Q(1)<=Q(0);Q(2)<=Q(1);Q(3)<=Q(2);

end if;

end process;

end behavioral;