-- ############################################################################
-- # Project    :    Leonardo CBT-Kernel                                      #
-- #                                                                          #
-- # Filename   :    encoders_decoders.vhd                                    #
-- #                                                                          #
-- # Component  :    encN : N-bit MSB-priority encoder. When no input         #
-- #                        is asserted the module is 1(0...), where          #
-- #                        the number of '0's is log2(N).                    #
-- #                                                                          #
-- # 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;
use work.useful_functions.all;

-- encN Entity Description
entity encN is
   generic(N: INTEGER := 4);
   port(
      DIN: in unsigned(N-1 downto 0);
      DOUT: out unsigned(log2(N)-1 downto 0)
   );
end encN;

-- encN Architecture Description
architecture rtl of encN is
begin
 
   PRIORITY_ENCODER_Process: process(DIN)
     VARIABLE DOUT_int: integer range 0 to N-1;    
   BEGIN
     DOUT_int := 0;         -- for the case that no '1' exists in DIN
     FOR i IN 0 TO N-1 LOOP
       IF DIN(i) = '1' THEN -- priority the lowest DIN(i) equal to '1'
         DOUT_int := i;
         exit;
       END IF;
     END LOOP;
     DOUT <= Conv_Unsigned(DOUT_int, log2(N));
   end process PRIORITY_ENCODER_Process;

end rtl;