Subversion Repositories t400

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

--

-- T400 Core

--

-- $Id: t400_por.vhd 179 2009-04-01 19:48:38Z arniml $

--

-- Wrapper for technology dependent power-on reset circuitry.

--

-- Altera Cyclone flavor.

--

-- Generate a reset upon power-on for specified number of clocks.

--

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

--

-- Copyright (c) 2006, Arnim Laeuger (arnim.laeuger@gmx.net)

--

-- All rights reserved

--

-- Redistribution and use in source and synthezised forms, with or without

-- modification, are permitted provided that the following conditions are met:

--

-- Redistributions of source code must retain the above copyright notice,

-- this list of conditions and the following disclaimer.

--

-- Redistributions in synthesized form must reproduce the above copyright

-- notice, this list of conditions and the following disclaimer in the

-- documentation and/or other materials provided with the distribution.

--

-- Neither the name of the author nor the names of other contributors may

-- be used to endorse or promote products derived from this software without

-- specific prior written permission.

--

-- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

-- AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,

-- THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

-- PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE

-- LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

-- CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

-- SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

-- INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

-- CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

-- ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

-- POSSIBILITY OF SUCH DAMAGE.

--

-- Please report bugs to the author, but before you do so, please

-- make sure that this is not a derivative work and that

-- you have the latest version of this file.

--

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

library ieee;

use ieee.std_logic_1164.all;

entity t400_por is

  generic (

    delay_g     : integer := 4;

    cnt_width_g : integer := 2

  );

  port (

    clk_i   : in  std_logic;

    por_n_o : out std_logic

  );

end t400_por;

library ieee;

use ieee.numeric_std.all;

architecture cyclone of t400_por is

  signal por_cnt_q : unsigned(cnt_width_g-1 downto 0)

    -- pragma translate_off

    -- initialize for simulation only

    := (others => '0')

    -- pragma translate_on

    ;

  signal por_n_q   : std_logic

    -- pragma translate_off

    -- initialize for simulation only

    := '0'

    -- pragma translate_on

    ;

  -- Specify power-up level of por counter and por source.

  -- Refer to "Quartus II Integrated Synthesis", section "Altera Attribute".

  attribute altera_attribute : string;

  attribute altera_attribute of por_cnt_q : signal is "-name POWER_UP_LEVEL LOW";

  attribute altera_attribute of por_n_q   : signal is "-name POWER_UP_LEVEL LOW";

begin

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

  -- Process por_cnt

  --

  -- Purpose:

  --   Generate a power-on reset for the specifiec number of clocks.

  --

  por_cnt: process (clk_i)

  begin

    if clk_i'event and clk_i = '1' then

      if por_cnt_q = delay_g-1 then

        por_n_q   <= '1';

      else

        por_cnt_q <= por_cnt_q + 1;

      end if;

    end if;

  end process por_cnt;

  --

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

  por_n_o <= por_n_q;

end cyclone;