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-- Hi Emacs, this is -*- mode: vhdl; -*-

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--

-- Up Syncronous counter of N bits with a/syncronous reset

--

-- Copyright (c) 2007 Javier Valcarce García, javier.valcarce@gmail.com

-- $Id: ctrm.vhd,v 1.1 2008-12-01 02:00:10 hharte Exp $

--

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-- This program 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 3 of the License, or

-- (at your option) any later version.

-- This program 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 program.  If not, see <http://www.gnu.org/licenses/>.

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library ieee;

use ieee.std_logic_1164.all;

use ieee.numeric_std.all;

entity ctrm is

  generic (

    M : integer := 08);

  port (

    reset : in  std_logic;              -- asyncronous reset

    clk   : in  std_logic;

    ce    : in  std_logic;              -- enable counting

    rs    : in  std_logic;              -- syncronous reset

    do    : out integer range (M-1) downto 0

    );

end ctrm;

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

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

architecture arch of ctrm is

  signal c : integer range (M-1) downto 0;

begin

  do <= c;

  process(reset, clk)

  begin

    if reset = '1' then

      c <= 0;

    elsif rising_edge(clk) then

      if ce = '1' then

        if rs = '1' then

          c <= 0;

        else

          c <= c + 1;

        end if;

      end if;

    end if;

  end process;

end arch;