source: rtems/c/src/lib/libbsp/m68k/mvme162/timer/timer.c @ 88d594a

/*  Timer_init()
 *
 *  This routine initializes the Tick Timer 1 on the MVME162 board.
 *
 *  Input parameters:  NONE
 *
 *  Output parameters:  NONE
 *
 *  NOTE: This routine will not work if the optimizer is enabled
 *        for some compilers.  The multiple writes
 *        may be optimized away.
 *
 *        It is important that the timer start/stop overhead be
 *        determined when porting or modifying this code.
 *
 *  COPYRIGHT (c) 1989, 1990, 1991, 1992, 1993, 1994.
 *  On-Line Applications Research Corporation (OAR).
 *  All rights assigned to U.S. Government, 1994.
 *
 *  This material may be reproduced by or for the U.S. Government pursuant
 *  to the copyright license under the clause at DFARS 252.227-7013.  This
 *  notice must appear in all copies of this file and its derivatives.
 *
 *  Modifications of respective RTEMS file: COPYRIGHT (c) 1994.
 *  EISCAT Scientific Association. M.Savitski
 *
 *  This material is a part of the MVME162 Board Support Package
 *  for the RTEMS executive. Its licensing policies are those of the
 *  RTEMS above.
 *
 *  $Id$
 */


#include <rtems.h>
#include <bsp.h>

/* Periodic tick interval */
#define TICK_INTERVAL                                   0x10000
#define TIMER_INT_LEVEL                         6

int Ttimer_val;
rtems_boolean Timer_driver_Find_average_overhead;

rtems_isr timerisr();

void Timer_initialize()
{
  (void) set_vector( timerisr, (VECTOR_BASE >> 28) * 0x10 + 0x8, 0 );

  Ttimer_val = 0;                                    /* clear timer ISR count */
  lcsr->vector_base = 0x67800000;                /* set vb, enable interrupts */
  lcsr->to_ctl = 0xE7;                /* prescaler to 1 MHz (see Appendix A1) */
  lcsr->timer_cmp_1 = TICK_INTERVAL;
  lcsr->timer_cnt_1 = 0;                                     /* clear counter */
  lcsr->board_ctl |= 7;        /* increment, reset-on-compare, clear-ovfl-cnt */

  lcsr->intr_level[0] |= TIMER_INT_LEVEL;                    /* set int level */
  lcsr->intr_ena |= 0x01000000;              /* enable tick timer 1 interrupt */
}

#define AVG_OVERHEAD      6  /* It typically takes 3.0 microseconds */
                             /* (6 countdowns) to start/stop the timer. */
#define LEAST_VALID       10 /* Don't trust a value lower than this */

int Read_timer()
{
  unsigned long                 total;

  total = (Ttimer_val * TICK_INTERVAL) + lcsr->timer_cnt_1;

  if ( Timer_driver_Find_average_overhead == 1 )
    return total;          /* in one-half microsecond units */

  if ( total < LEAST_VALID )
    return 0;            /* below timer resolution */

  return (total-AVG_OVERHEAD);                  /* in musec units */
}

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;
}