-- ############################################################################
-- # Project    :    Leonardo CBT-Kernel                                      #
-- #                                                                          #
-- # Filename   :    special.vhd                                              #
-- #                                                                          #
-- # Component  :    bin_bcdX : Binary to X-digits BCD converter with         #
-- #                            error output.                                 #
-- #                                                                          #
-- # Model      :    rtl                                                      #
-- #                                                                          #
-- # Designer   :    S. Theoharis,N. Zervas                                   #
-- # Institute  :    VLSI Design Lab., University of Patras                   #
-- # Date       :    01.05.1999                                               #
-- ############################################################################

library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.std_logic_arith.all;

-- bin_bcdX Entity Description
ENTITY bin_bcdX IS
	GENERIC(X : integer := 2);
	PORT(
		D: IN unsigned((4*X-1) DOWNTO 0);
		Q: OUT unsigned((3*X+1) DOWNTO 0);
		E: OUT std_ulogic
	);
end bin_bcdx;

-- bin_bcdx Architecture Description
ARCHITECTURE rtl OF bin_bcdX IS
    CONSTANT N: integer :=3*X+2; -- length of input in bits
    CONSTANT M: integer :=X;  -- length of output in BCD digits
BEGIN
    Convert_Process:process(D)
	VARIABLE r: unsigned(N+3 DOWNTO 0);
    BEGIN
	r:=(OTHERS=>'0');
	IF D(N-1 DOWNTO N-3)>"100" THEN
		r(3 DOWNTO 0):=('0' & D(N-1 DOWNTO N-3)) + "0011";
	ELSE
		r(3 DOWNTO 0):='0' & D(N-1 DOWNTO N-3);
	END IF;
	FOR i IN 0 TO N-5 loop
		r:=r(r'LEFT-1 DOWNTO 0) & D(N-4-i);
		FOR j IN 0 TO M-1 loop
			IF j*3<i+2 THEN
				IF r((j*4)+3 DOWNTO j*4)>"0100" THEN
					r((j*4)+3 DOWNTO j*4):=r((j*4)+3 DOWNTO j*4) + "0011";
				END IF;
			END IF;
		END loop; 
	END loop;
	r:=r(r'LEFT-1 DOWNTO 0) & D(0);
	Q<=r((4*M)-1 DOWNTO 0);
	IF Conv_Integer(r(r'LEFT DOWNTO 4*M),0)/=0 THEN
		E<='1';
	ELSE
		E<='0';
	END IF;
    END PROCESS Convert_Process;
END rtl;