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       = CAM_BIT_FIRST     --

--  version      = 1.0               --

--  last update  = 30/05/98          --

--  author       = Jose Nunez        --

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

-- FUNCTION

-- basic bit element of the CAM array

--  PIN LIST

--  SEARCH   = input search data bit

--  PREVIOUS = data from the previous location in the array

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

--  CLK      = master clock

--  DOUT     = output of the data latch

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

library ieee;

use ieee.std_logic_1164.all;

entity CAM_BIT_FIRST is

port

(

        SEARCH : in bit;

        PREVIOUS : in bit;

        CLEAR : in bit ;

        RESET: in bit;

        CLK : in bit ;

        DOUT : out bit;

        MATCH : out bit

);

end CAM_BIT_FIRST;

architecture BIT1 of CAM_BIT_FIRST is

signal TEMP_Q : bit;

begin

COMB : process(CLK,CLEAR)

begin

if (CLEAR = '0') then

        TEMP_Q <= '0';                   -- check for CLEAR active

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

        if (RESET = '0') then

        TEMP_Q <= '0';                   -- check for CLEAR active

        else

        TEMP_Q <= PREVIOUS;     -- get data from previous location

        end if;

end if;

end process COMB;

DOUT <= TEMP_Q;

MATCH <= SEARCH xor TEMP_Q;             -- match goes low if SEARCH = TEMP_Q

end BIT1;