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/* $Id: memtest.hh,v 1.1 2008-06-20 17:51:23 sybreon Exp $

**

** MEMORY TEST FUNCTIONS

** Copyright (C) 2008 Shawn Tan 

**

** This file is part of AEMB.

**

** AEMB 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.

**

** AEMB 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 AEMB.  If not, see .

*/

#ifndef MEMTEST_HH

#define MEMTEST_HH

/**

   WALKING ONES TEST

   Checks individual bit lines in O(1)

   http://www.embedded.com/2000/0007/0007feat1list1.htm

*/

inline int memtestDataBus(volatile int *ram)

{

  for (int i=1; i!=0; i<<=1)

    {

      *ram = i; // write test value

      if (*ram != i) // read back test

        return i;

    }

  return 0; // 0 if success

}

/**

   POWERS OF TWO TEST

   Checks the address lines

   http://www.embedded.com/2000/0007/0007feat1list2.htm

 */

inline int memtestAddressBus(volatile int *ram, int len)

{

  const int p = 0xAAAAAAAA;

  const int q = 0x55555555;

  // prefill memory

  for (int i=1; (i & (len-1))!=0 ; i<<=1)

    {

      ram[i] = p;

    }

  // check 1 - stuck high

  ram[0] = q;

  for (int i=1; (i & (len-1))!=0 ; i<<=1)

    {

      if (ram[i] != p)

        return ram[i];

    }

  ram[0] = p;

  // check 2 - stuck low

  for (int j=1; (j & (len-1))!=0 ; j<<=1)

    {

      ram[j] = q;

      for (int i=1; (i & (len-1))!=0 ; i<<=1)

        {

          if ((ram[i] != p) && (i != j))

            return ram[i];

        }

      ram[j] = p;

    }

  return 0;

}

/**

   INCREMENT TEST

   Checks the entire memory device

   http://www.embedded.com/2000/0007/0007feat1list1.htm

 */

inline int memtestDeviceMem(volatile int *ram, int len)

{

  // prefill the memory

  for (int p=1, i=0; i

    {

      ram[i] = p;

    }

  // pass 1 - check and invert

  for (int p=1, i=0; i

    {

      if (ram[i] != p)

        return ram[i];

      ram[i] = ~p;

    }

  // pass 2 - check and zero

  for (int p=1, i=0; i

    {

      if (ram[i] != ~p)

        return ram[i];

      ram[i] = 0;

    }

  return 0;

}

#endif

/*

  $Log: not supported by cvs2svn $

 */