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/*  timer.c

 *

 *  This file implements a benchmark timer using the General Purpose Timer on

 *  the MEC.

 *

 *  COPYRIGHT (c) 1989-1999.

 *  On-Line Applications Research Corporation (OAR).

 *

 *  The license and distribution terms for this file may be

 *  found in found in the file LICENSE in this distribution or at

 *  http://www.OARcorp.com/rtems/license.html.

 *

 *  Ported to ERC32 implementation of the SPARC by On-Line Applications

 *  Research Corporation (OAR) under contract to the European Space

 *  Agency (ESA).

 *

 *  ERC32 modifications of respective RTEMS file: COPYRIGHT (c) 1995.

 *  European Space Agency.

 *

 *  $Id: timer.c,v 1.2 2001-09-27 12:01:02 chris Exp $

 */

#include <assert.h>

#include <bsp.h>

rtems_unsigned64 Timer_driver_Start_time;

rtems_boolean Timer_driver_Find_average_overhead;

void Timer_initialize()

{

  /*

   *  Timer runs long and accurate enough not to require an interrupt.

   */

  Timer_driver_Start_time = PPC_Get_timebase_register();

}

#define AVG_OVERHEAD     24  /* It typically takes 24 instructions */

                             /*     to start/stop the timer. */

#define LEAST_VALID       1  /* Don't trust a value lower than this */

                             /* psim can count instructions. :) */

int Read_timer()

{

  rtems_unsigned64  clicks;

  rtems_unsigned64  total64;

  rtems_unsigned32  total;

  /* approximately CLOCK_SPEED clicks per microsecond */

  clicks = PPC_Get_timebase_register();

  assert( clicks > Timer_driver_Start_time );

  total64 = clicks - Timer_driver_Start_time;

  assert( total64 <= 0xffffffff );  /* fits into a unsigned32 */

  total = (rtems_unsigned32) total64;

  if ( Timer_driver_Find_average_overhead == 1 )

    return total;          /* in one microsecond units */

  if ( total < LEAST_VALID )

    return 0;            /* below timer resolution */

  return total - AVG_OVERHEAD;

}

rtems_status_code Empty_function( void )

{

  return RTEMS_SUCCESSFUL;

}

void Set_find_average_overhead(

  rtems_boolean find_flag

)

{

  Timer_driver_Find_average_overhead = find_flag;

}