-------------------------------------------------------------------------------
-- Title         : Filtre gaussien optimise
-- Project       : 
-------------------------------------------------------------------------------
-- File          : gaussien.vhd
-- Author        :   <nouel@szut>
-- Created       : 1999/10/04
-- Last modified : 1999/10/04
-------------------------------------------------------------------------------
-- Description : moyenne de 9 pixels pris individuelement avec frequence de 
--               sorie divisee par trois
--              Version synthetisable pipelinee
--              On calcule une somme ponderre 1-2-1 sur 3 pixels
--              Puis on calcule la meme somme ponderee sur trois sommes
----   1 2 1    = 1 S1
--     2 4 2    = 2 S2
---    1 2 1    = 1 S3
-------------------------------------------------------------------------------
-- Modification history :
-- 1999/10/04 : created
-------------------------------------------------------------------------------

LIBRARY ieee; 
USE ieee.std_logic_1164.ALL;

USE work.utils.ALL;

ENTITY filtre IS
    
    PORT (h : IN std_ulogic;  		-- horloge
	  init : IN std_ulogic;  	-- reset
	  pixel : IN natural RANGE 0 TO 255;
	  pix_calcul : OUT natural RANGE 0 TO 255 ;
	  ready_in : IN std_ulogic;  	-- protocole d'entree
	  ack_in : OUT std_ulogic;
	  ready_out : OUT std_ulogic;
	  ack_out : IN std_ulogic);

END filtre;


-- la sortie pix_out est divisee par 16 donc il y a une virgule fixe implicite
ARCHITECTURE gaussien  OF filtre IS 
  SIGNAL somme1, somme2, somme3 : natural RANGE 0 TO 4*255;
  SIGNAL autorise : std_ulogic;-- pour entree donnees
 SIGNAL fin_calcul : std_ulogic;
BEGIN 
 
  autorise <= NOT( fin_calcul)  AND ready_in AND NOT  (ack_OUT );
  
 ready_OUT <= fin_calcul;
  
un_seul: PROCESS (init, h, ack_out)              -- init asynchrone
  VARIABLE comptage : natural RANGE 0 TO 2;
  VARIABLE accum1: natural RANGE 0 TO 4*255;
  VARIABLE accum2 : natural RANGE 0 TO 16*255;
BEGIN 
     IF init = '1' OR ack_out = '1'THEN  fin_calcul <= '0';
	  fin_calcul <= '0';
	  ELSIF init = '1' THEN
       comptage := 0;
       accum1 := 0;
       accum2 := 0;
       somme1 <= 0;
       somme2 <= 0;
       somme3 <= 0;
       pix_calcul <= 0;
      
     ELSIF front_montant(h) THEN 
         IF autorise = '1' THEN 
           CASE comptage IS
             WHEN 0  => comptage := 1 ;
                  accum1 := pixel;
                  accum2 := somme1;
             WHEN 1  => comptage := 2;
                  accum1 := accum1 + 2*pixel;
                  accum2 := accum2 + 2*somme2;
             WHEN 2 =>  comptage := 0;
                  accum1 := accum1 + pixel;
                  accum2 := accum2 + somme3;
                  somme3 <= accum1;
                  somme2 <= somme3;
                  somme1 <= somme2;
                  pix_calcul <= accum2/16;
                  fin_calcul <= '1';
           END CASE;
         END IF; 
     END IF;
END PROCESS;
 
     protoc_in : PROCESS (h, init)
		       
     BEGIN  -- PROCESS entree
       IF init = '1' THEN
         ack_in <= '0';
       ELSIF front_montant(h) THEN
         ack_IN <= autorise;
       END IF;
     END PROCESS protoc_in;

END gaussien ;