How to design 4 bit counter using hald adder circuit ?

[seemagoyal44]

design 4 bit counter using hald adder circuit

 

[karthiga05]

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

entity counter4 is
port(countut std_logic_vector(3 downto 0);
clk:in std_logic;
reset:in std_logic);
end counter4;

architecture behav_counter4 of counter4 is

component ha port (a: in std_logic;
b: in std_logic;
sum: out std_logic;
c_out: out std_logic);
end component;

component fa port (a, b, cin : in std_logic;
sum, c_out : out std_logic);
end component;

signal ain,s,c:std_logic_vector(3 downto 0) :="0000";
signal bin:std_logic_vector(3 downto 0):="0001";

--configuration specification
for all:ha use entity work.ha(rtl);
for all:fa use entity work.fa(fa_behav);

begin
u1:ha port map(a => ain(0), b => bin(0), sum => s(0), c_out => c(0));
u2:fa port map(a => ain(1), b => bin(1), sum => s(1), cin => c(0), c_out => c(1));
u3:fa port map(a => ain(2), b => bin(2), sum => s(2), cin => c(1), c_out => c(2));
u4:fa port map(a => ain(3), b => bin(3), sum => s(3), cin => c(2), c_out => c(3));


counterrocess(clk, reset) --process(sensitivity list)
begin
if reset'event and (reset = '1') then
s <= (others => '0');

elsif clk'event and (clk='1') then
ain <= c xor ain;
s <= ain xor bin;
c <= s and c;
ain <= c xor ain;

end if;
end process;

count <= s;

end behav_counter4;


this is what i have. but it has some error. it doesnt loop.