-- ############################################################################
-- # Project    :    Leonardo CBT-Kernel                                      #
-- #                                                                          #
-- # Filename   :    special.vhd                                              #
-- #                                                                          #
-- # Component  :    bcdX_bin : X-digits BCD to binary 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;

ENTITY bcdX_bin IS
	GENERIC(X : integer := 2);
	PORT(
		D: IN unsigned((3*X+1) DOWNTO 0);
		Q: OUT unsigned((4*X-1) DOWNTO 0);
		E: OUT std_ulogic
	);
END bcdX_bin;

-- bcNx_bin Architecture Description
ARCHITECTURE rtl OF bcdx_bin IS
	CONSTANT N: integer :=4*X; -- width of D in bits
	CONSTANT M: integer :=X; -- width of D in bcd digits
BEGIN
	Convert_Process:process(D)
		VARIABLE p: unsigned(N+3 DOWNTO 0);
		VARIABLE error: std_ulogic:='0';
	BEGIN
		p:=Conv_Unsigned(0, N) & D(N-1 DOWNTO N-4);
		error:='0';
		if (D(N-1 DOWNTO N-4)>="1010") then
			error:='1';
                END if;
		FOR i IN M-2 DOWNTO 0 loop
			if (d((i*4)+3 downto i*4)>"1010") then
				error:='1';
                        END if;
			p:=p(N-1 downto 0) * "1010" + 
                        Conv_Unsigned(Conv_Integer(('0' & d((i*4)+3 DOWNTO (i*4))),0),N+4);
		END loop;
		Q<=p(N-1 downto 0);
		E<=error;
	END process Convert_Process;
END rtl;