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--

-- Clock divider (clock enable generator)

--

-- Author:   Sebastian Witt

-- Date:     27.01.2008

-- 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.std_logic_unsigned.all;

USE IEEE.numeric_std.all;

entity slib_clock_div is

    generic (

        RATIO       : integer := 4      -- Clock divider ratio

    );

    port (

        CLK         : in std_logic;     -- Clock

        RST         : in std_logic;     -- Reset

        CE          : in std_logic;     -- Clock enable input

        Q           : out std_logic     -- New clock enable output

    );

end slib_clock_div;

architecture rtl of slib_clock_div is

    -- Signals

    signal iQ       : std_logic;                  -- Internal Q

    signal iCounter : integer range 0 to RATIO-1; -- Counter

begin

    -- Main process

    CD_PROC: process (RST, CLK)

    begin

        if (RST = '1') then

            iCounter <= 0;

            iQ       <= '0';

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

            iQ <= '0';

            if (CE = '1') then

                if (iCounter = (RATIO-1)) then

                    iQ <= '1';

                    iCounter <= 0;

                else

                    iCounter <= iCounter + 1;

                end if;

            end if;

        end if;

    end process;

    -- Output signals

    Q <= iQ;

end rtl;