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--This library is free software; you can redistribute it and/or

--modify it under the terms of the GNU Lesser General Public

--License as published by the Free Software Foundation; either

--version 2.1 of the License, or (at your option) any later version.

--This library is distributed in the hope that it will be useful,

--but WITHOUT ANY WARRANTY; without even the implied warranty of

--MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

--Lesser General Public License for more details.

--You should have received a copy of the GNU Lesser General Public

--License along with this library; if not, write to the Free Software

--Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

-- e_mail : j.l.nunez-yanez@byacom.co.uk

---------------------------------

--  ENTITY       =  RLI_DCU    --

--  version      =  1.0        --

--  last update  =  25/11/99   --

--  author       =  Jose Nunez --

---------------------------------

-- FUNCTION

-- RLI decoding control unit

--  PIN LIST

--  RL_DETECTED : detection of a RL code in the main decoder

--  LOCATION_IN : decoded location in the main decoder

--  MATCH_TYPE_IN : decoded match type in the main decoder

--  END_COUNT : end of RLI count indication

--  CLEAR : asyncronus clear 

--  CLK : master clock

--  LOCATION_OUT : location output of the DCU

--  MATCH_TYPE_OUT : match type output of the DCU

--  SET_LENGTH_TO_ZERO : run length active no more data needed

library ieee;

use ieee.std_logic_1164.all;

entity RLI_DCU is

port

(

      RL_DETECTED : in bit;

      LOCATION_IN : in bit_vector(3 downto 0);

      MATCH_TYPE_IN : in bit_vector(3 downto 0);

        MASK_IN : in bit_vector(4 downto 0);

        FULL_HIT_IN : in bit;

          END_COUNT : in bit;

          CLEAR : in bit;

          RESET : in bit;

          CLK : in bit ;

          LOCATION_OUT : out bit_vector(3 downto 0);

          MATCH_TYPE_OUT : out bit_vector(3 downto 0);

          MASK_OUT : out bit_vector(4 downto 0);

          FULL_HIT_OUT : out bit;

          SET_LENGTH_TO_ZERO : out bit

);

end RLI_DCU;

architecture STRUCTURAL of RLI_DCU is

signal CURRENT_STATE : bit_vector(1 downto 0);

signal NEXT_STATE : bit_vector(1 downto 0);

begin

STATES : process (FULL_HIT_IN,RL_DETECTED,CURRENT_STATE,LOCATION_IN,MATCH_TYPE_IN,END_COUNT)

begin

case CURRENT_STATE is

        when "00" =>  -- state 0 normal output

                if (RL_DETECTED = '1') then

                        NEXT_STATE <= "01";

                else

                        NEXT_STATE <= CURRENT_STATE;

                end if;

                LOCATION_OUT <= LOCATION_IN;

                MATCH_TYPE_OUT <= MATCH_TYPE_IN;

                FULL_HIT_OUT <= FULL_HIT_IN;

                SET_LENGTH_TO_ZERO <= '0';

         when "01" =>  -- state 1 length set to zero

                if (END_COUNT = '1') then

                        NEXT_STATE <= "00";

                else

                        NEXT_STATE <= CURRENT_STATE;

                end if;

                LOCATION_OUT <= LOCATION_IN;

                MATCH_TYPE_OUT <= "0000";

                FULL_HIT_OUT <= '0'; -- active at zero

                SET_LENGTH_TO_ZERO <= '1';

        when "10" =>

                NEXT_STATE <= "00";

                LOCATION_OUT <= "0000";

                MATCH_TYPE_OUT <= "0000";

                FULL_HIT_OUT <= '0';

                SET_LENGTH_TO_ZERO <= '0';

        when others =>

                NEXT_STATE <= "00";

                LOCATION_OUT <= "0000";

                MATCH_TYPE_OUT <= "0000";

                SET_LENGTH_TO_ZERO <= '0';

                FULL_HIT_OUT <= '1';

end  case;

end process STATES;

MASK_OUT <= MASK_IN;

FLIP_FLOPS : process(CLK, CLEAR, NEXT_STATE)

begin

if (CLEAR = '0') then

        CURRENT_STATE <= "00"; --state 0

elsif ((CLK'event) and (CLK='1')) then

        if (RESET = '0') then

                CURRENT_STATE <= "00"; --state 0

        else

                CURRENT_STATE <= NEXT_STATE;

        end if;

end if;

end process FLIP_FLOPS;

end STRUCTURAL;