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       = MASK_WORD    --

--  version      = 1.0         --

--  last update  = 3/05/01    --

--  author       = Jose Nunez  --

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

-- FUNCTION

-- 4 bit mask element of the CAM array.

--  PIN LIST

--  SEARCH    = input search mask word

--  PREVIOUS  = mask word from the previous location in the array

--  MOVE      = movement control

--  CLEAR     = asynchronous clear of the data latch (active LOW)

--  CLK       = master clock

--  DOUT      = output of the mask latch

--  MATCH     = indicates a match between search bit and mask bit (active LOW)

library ieee;

use ieee.std_logic_1164.all;

library dzx;

use dzx.bit_utils.all;

entity MASK_WORD is

port

(

        SEARCH : in bit_vector(3 downto 0);

        PREVIOUS : in bit_vector(3 downto 0);

        MOVE : in bit;

        CLEAR : in bit ;

        RESET : in bit;

        CLK : in bit ;

        DOUT : out bit_vector(3 downto 0);

        SAME_LENGTH_2 : out bit;

        SAME_LENGTH_3 : out bit;

        SAME_LENGTH_4 : out bit;

        MATCH : out bit_vector(3 downto 0)

);

end MASK_WORD;

architecture WORD1 of MASK_WORD is

component MASK_BIT

port

(

        SEARCH : in bit;

        PREVIOUS : in bit;

        MOVE : in bit;

        CLEAR : in bit;

    RESET : in bit;

        CLK : in bit ;

        DOUT : out bit;

        MATCH : out bit

);

end component;

signal MATCH_AUX : bit_vector(3 downto 0);

signal SAME_LENGTH_2_AUX : bit;

signal SAME_LENGTH_3_AUX : bit;

signal SAME_LENGTH_4_AUX : bit;

signal SAME_LENGTH_AUX : bit;

signal DOUT_AUX : bit_vector(3 downto 0);

begin

M_WORD : for I in 3 downto 0 generate

        WORD_BIT: MASK_BIT

        port map

        (

                SEARCH =>SEARCH(I),

                PREVIOUS =>PREVIOUS(I),

                MOVE =>MOVE,

                CLEAR =>CLEAR,

                 RESET =>RESET,

                CLK =>CLK,

                DOUT =>DOUT_AUX(I),

                MATCH =>MATCH_AUX(I)

        );

end generate;

SAME_LENGTH_AUX <= nor_bits(SEARCH xor DOUT_AUX); -- same length detected

MATCH <= MATCH_AUX;

-- which length

SAME_LENGTH_2_AUX <= SEARCH(3) and SEARCH(2) and not(SEARCH(1)) and not(SEARCH(0));

SAME_LENGTH_3_AUX <= SEARCH(3) and SEARCH(2) and SEARCH(1) and not(SEARCH(0));

SAME_LENGTH_4_AUX <= SEARCH(3) and SEARCH(2) and SEARCH(1) and SEARCH(0);

SAME_LENGTH_2 <= SAME_LENGTH_AUX and SAME_LENGTH_2_AUX;

SAME_LENGTH_3 <= SAME_LENGTH_AUX and SAME_LENGTH_3_AUX;

SAME_LENGTH_4 <= SAME_LENGTH_AUX and SAME_LENGTH_4_AUX;

DOUT <= DOUT_AUX;

end WORD1;