library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;


entity machine is
  port (
    clock : IN std_logic;
    START : IN std_logic;
    RESET : IN std_logic;
    INPUT : IN std_logic_vector(7 downto 0);
    OUTPUT : OUT std_logic_vector(7 downto 0);  
    count : OUT std_logic_vector(7 downto 0)
  ) ;
end machine;

architecture behavior of machine is

type etat is (attente, init, calcul, fin);
type cal is ('0','1');
signal state : etat := attente;
signal done : cal; 

BEGIN
    
  Racine : process(clock)
    variable X : integer;
    variable V : integer;
    variable Z : integer;
    variable n : integer := 5;
    variable cond : integer; 
    variable i : integer;
    
    begin 
      if(rising_edge(clock)) then
        if RESET = '1' then
          state <= attente;
        end if;
        
        case state is
          when attente => 
            if START = '1' then
              state <= init;
            else 
            	 state <= attente;
            end if;
            done <= '0';
      
        when init =>
          X := to_integer(unsigned(INPUT));
          V := 256;
          Z := 0;
          i := 5;
          done <= '0';
          state <= calcul;
      
        when calcul =>
          Z := Z+V;
          cond := X-Z;
          if cond >= 0 then
            X := X-Z;
            Z := (Z+V)/2;
          else
            Z := (Z-V)/2;
          end if;
          V := V/4;
          i := i-1;
          count <= std_logic_vector(to_unsigned(i, count'length));
                     
          done <= '0';
          if i = 0 then
            state <= fin;
          else
            state <= calcul;
          end if;
      
        when fin =>
          done <= '1';
          OUTPUT <= std_logic_vector(to_unsigned(Z, OUTPUT'length));
          if START = '1' then
            state <= fin;
          else
            state <= attente;
          end if;  
          
       	when others =>
          state <= attente;
          
      end case;
    end if;
  end process Racine;

end behavior;