Subversion Repositories xmatchpro

--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_COUNTER        --

--  version      = 1.0                --

--  last update  = 22/11/99           --

--  author       = Jose Nunez         --

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

-- FUNCTION

-- 8 bit counter for the RLI process

--  PIN LIST

--  LOAD = load external data ( for decompression )

--  LOCATION_ZERO = run length at location zero

--  SAME_POSITION = to detect a full match at the same position

--  DATA = external data ( for decompression )

--  ENABLE = enable count if not enable then zero

--  CLEAR = asyncronus clear of the counter

--  CLK   = master clock

--  COUNT = count output

--  RL_DETECTED = run length internal detection

library ieee,dzx;

use ieee.std_logic_1164.all;

use dzx.bit_arith.all;

use dzx.bit_utils.all;

entity RLI_COUNTER_C is

port (

          MOVE_ENABLE : in bit;

          ENABLE_C : in bit;

          LOCATION_ZERO : in bit;

          SAME_POSITION : in bit;

          CLEAR : in bit;

          RESET : in bit;

          CLK : in bit;

          COUNT : out bit_vector(7 downto 0);

          RL_DETECTED : out bit

          );

end RLI_COUNTER_C;

architecture STRUCTURAL of RLI_COUNTER_C is

signal NEXT_COUNT : bit_vector(7 downto 0);

signal CURRENT_COUNT : bit_vector(7 downto 0);

signal ENABLE_INT : bit;

signal COUNTER_RESET : bit;

begin

ENABLE_INT <= ENABLE_C;

STATES: process (MOVE_ENABLE, ENABLE_INT, SAME_POSITION, CURRENT_COUNT, COUNTER_RESET, LOCATION_ZERO)

begin

if (MOVE_ENABLE = '0') then

        case CURRENT_COUNT is

        when "00000000" =>

                if( ENABLE_INT = '1') then

                        NEXT_COUNT <= "00000001";

                else

                        NEXT_COUNT<= "00000000";

                end if;

        when "11111111" =>

                if( ENABLE_INT = '1') then

                        NEXT_COUNT <= "00000001";

                else

                        NEXT_COUNT<= "00000000";

                end if;

        when others =>

                if ((SAME_POSITION = '1' and COUNTER_RESET = '0') or (LOCATION_ZERO = '1')) then

                        NEXT_COUNT <= CURRENT_COUNT + "00000001";

                elsif (ENABLE_INT = '1') then

                        NEXT_COUNT <= "00000001";

                else

                        NEXT_COUNT <= "00000000";

                end if;

        end case;

else

        NEXT_COUNT <= CURRENT_COUNT; -- "00000000";

end if;

end process STATES;

INCREASE_COUNT : process (LOCATION_ZERO,CURRENT_COUNT)

begin

if(LOCATION_ZERO='0' and CURRENT_COUNT = "00000101") then

        COUNTER_RESET <= '1';

else

        COUNTER_RESET <= '0';

end if;

end process INCREASE_COUNT;

COUNTING : process (CLK,CLEAR)

begin

        -- asynchronous RESET signal forces all outputs LOW

      if (CLEAR = '0') then

            CURRENT_COUNT <= "00000000";

            -- check for +ve clock edge

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

                            if (RESET = '0') then

                                         CURRENT_COUNT <= "00000000";

                    else

                                        CURRENT_COUNT <= NEXT_COUNT;

                            end if;

         end if;

end process COUNTING;

RL_DETECTED <= '1' when CURRENT_COUNT > "00000001" else '0'; -- run length detection

COUNT <= CURRENT_COUNT;

end STRUCTURAL;