------------------------------------------------------------------------------
--  This file is a part of the LPP VHDL IP LIBRARY
--  Copyright (C) 2009 - 2010, Laboratory of Plasmas Physic - CNRS
--
--  This program is free software; you can redistribute it and/or modify
--  it under the terms of the GNU 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 General Public License for more details.
--
--  You should have received a copy of the GNU General Public License
--  along with this program; if not, write to the Free Software
--  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 
-------------------------------------------------------------------------------
--                    Author : Alexis Jeandet
--                     Mail : alexis.jeandet@lpp.polytechnique.fr
----------------------------------------------------------------------------
LIBRARY ieee;
USE ieee.std_logic_1164.ALL;
USE IEEE.numeric_std.ALL;

ENTITY RAM_CEL_N IS
  GENERIC (
    size : INTEGER);
  PORT(
    WD           : IN  STD_LOGIC_VECTOR(size-1 DOWNTO 0);
    RD           : OUT STD_LOGIC_VECTOR(size-1 DOWNTO 0);
    WEN, REN     : IN  STD_LOGIC;
    WADDR        : IN  STD_LOGIC_VECTOR(7 DOWNTO 0);
    RADDR        : IN  STD_LOGIC_VECTOR(7 DOWNTO 0);
    RWCLK, RESET : IN  STD_LOGIC
    ) ;
END RAM_CEL_N;



ARCHITECTURE ar_RAM_CEL OF RAM_CEL_N IS
  TYPE     RAMarrayT IS ARRAY (0 TO 255) OF STD_LOGIC_VECTOR(size-1 DOWNTO 0);
  CONSTANT vector_null : STD_LOGIC_VECTOR(size-1 DOWNTO 0) := (OTHERS => '0');
  SIGNAL   RAMarray    : RAMarrayT                         := (OTHERS => vector_null);
  SIGNAL   RD_int      : STD_LOGIC_VECTOR(size-1 DOWNTO 0);

BEGIN

  RD_int <= RAMarray(to_integer(UNSIGNED(RADDR)));


  PROCESS(RWclk, reset)
  BEGIN
    IF reset = '0' THEN
      RD <= vector_null;
      rst : FOR i IN 0 TO 255 LOOP
        RAMarray(i) <= vector_null;
      END LOOP;

    ELSIF RWclk'EVENT AND RWclk = '1' THEN
      IF REN = '0' THEN
        RD <= RD_int;
      END IF;

      IF WEN = '0' THEN
        RAMarray(to_integer(UNSIGNED(WADDR))) <= WD;
      END IF;

    END IF;
  END PROCESS;
  
END ar_RAM_CEL;