source: rtems/c/src/lib/libbsp/m68k/mrm332/clock/ckinit.c @ f68401e

/*  Clock_init()
 *
 *  This routine initailizes the periodic interrupt timer on
 *  the Motorola 68332.
 *
 *  Input parameters:  NONE
 *
 *  Output parameters:  NONE
 *
 *  COPYRIGHT (c) 1989-1999.
 *  On-Line Applications Research Corporation (OAR).
 *
 *  The license and distribution terms for this file may be
 *  found in the file LICENSE in this distribution or at
 *  http://www.rtems.com/license/LICENSE.
 */

#include <stdlib.h>
#include <bsp.h>
#include <mrm332.h>

#define CLOCK_VECTOR   MRM_PIV

uint32_t         Clock_isrs;        /* ISRs until next tick */
volatile uint32_t         Clock_driver_ticks;
                                    /* ticks since initialization */
rtems_isr_entry  Old_ticker;

void Clock_exit( void );

/*
 * These are set by clock driver during its init
 */

rtems_device_major_number rtems_clock_major = ~0;
rtems_device_minor_number rtems_clock_minor;

rtems_isr Clock_isr(rtems_vector_number vector)
{
  Clock_driver_ticks += 1;

  if ( Clock_isrs == 1 ) {
    rtems_clock_tick();
    Clock_isrs = rtems_configuration_get_microseconds_per_tick() / 1000;
  }
  else
    Clock_isrs -= 1;
}

void Install_clock(
  rtems_isr_entry clock_isr
)
{
  Clock_driver_ticks = 0;
  Clock_isrs = rtems_configuration_get_microseconds_per_tick() / 1000;

  Old_ticker = (rtems_isr_entry) set_vector( clock_isr, CLOCK_VECTOR, 1 );

  /* enable 1mS interrupts */
  *PITR = (unsigned short int)( SAM(0x09,0,PITM) );/* load counter */
  *PICR = (unsigned short int)                     /* enable interrupt */
    ( SAM(ISRL_PIT,8,PIRQL) | SAM(CLOCK_VECTOR,0,PIV) );

  atexit( Clock_exit );
}

void Clock_exit( void )
{
  /* shutdown the periodic interrupt */
  *PICR = (unsigned short int)
    ( SAM(0,8,PIRQL) | SAM(CLOCK_VECTOR,0,PIV) );
  /*     ^^ zero disables interrupt */

  /* do not restore old vector */
}

rtems_device_driver Clock_initialize(
  rtems_device_major_number major,
  rtems_device_minor_number minor,
  void *pargp
)
{
  Install_clock( Clock_isr );

  /*
   * make major/minor avail to others such as shared memory driver
   */

  rtems_clock_major = major;
  rtems_clock_minor = minor;

  return RTEMS_SUCCESSFUL;
}