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--

-- Input filter

--

-- Author:   Sebastian Witt

-- Data:     06.03.2008

-- Version:  1.0

--

-- This code 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 code 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., 59 Temple Place, Suite 330,

-- Boston, MA  02111-1307  USA

--

LIBRARY IEEE;

USE IEEE.std_logic_1164.all;

USE IEEE.numeric_std.all;

entity slib_input_filter is

    generic (

        SIZE        : natural := 4      -- Filter counter size

    );

    port (

        CLK         : in std_logic;     -- Clock

        RST         : in std_logic;     -- Reset

        CE          : in std_logic;     -- Clock enable

        D           : in std_logic;     -- Signal input

        Q           : out std_logic     -- Signal output

    );

end slib_input_filter;

architecture rtl of slib_input_filter is

    signal iCount : integer range 0 to SIZE;

begin

    IF_D: process (RST, CLK)

    begin

        if (RST  = '1') then

            iCount <= 0;

            Q      <= '0';

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

            -- Input counter

            if (CE = '1' ) then

                if (D = '1' and iCount /= SIZE) then

                    iCount <= iCount + 1;

                elsif (D = '0' and iCount /= 0) then

                    iCount <= iCount - 1;

                end if;

            end if;

            -- Output

            if (iCount = SIZE) then

                Q <= '1';

            elsif (iCount = 0) then

                Q <= '0';

            end if;

        end if;

    end process;

end rtl;