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/*  Timer_init()

 *

 *  This routine initializes the MC68230 timer on the Motorola IDP board.

 *

 *  Input parameters:  NONE

 *

 *  Output parameters:  NONE

 *

 *  NOTE: This routine will not work if the optimizer is enabled

 *        for some compilers.  The multiple writes to the MC68230

 *        may be optimized away.

 *

 *        It is important that the timer start/stop overhead be

 *        determined when porting or modifying this code.

 *

 *  Code Modified for the MC68230 by Doug McBride, Colorado Space Grant College

 *

 *  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.OARcorp.com/rtems/license.html.

 *

 *  $Id: timer.c,v 1.2 2001-09-27 12:00:12 chris Exp $

 */

#include <rtems.h>

#include <bsp.h>

#include <motorola/mc68230.h>

#define TIMER_VECTOR 0x4D

int Ttimer_val;

rtems_boolean Timer_driver_Find_average_overhead;

rtems_isr timerisr();

void Timer_initialize()

{

  (void) set_vector( timerisr, TIMER_VECTOR, 0 );  /* install ISR */

  Ttimer_val = 0;                          /* clear timer ISR count */

  /* some PI/T initialization stuff here */

  /* Set up the interrupt vector on the MC68230 chip:

     TIVR = TIMER_VECTOR; */

  MC68230_WRITE (TIVR, TIMER_VECTOR);

  /* Set CPRH through CPRL to maximum count to reduce interrupt overhead

      CPRH = 0xFF;

      CPRM = 0xFF;

      CPRL = 0xFF; */

  MC68230_WRITE (CPRH, 0xFF);

  MC68230_WRITE (CPRM, 0xFF);

  MC68230_WRITE (CPRL, 0xFF);

  /* Enable timer and use it as an external periodic interrupt generator

      TCR = 0xA1; */

  MC68230_WRITE (TCR, 0xA1);

}

#define AVG_OVERHEAD      9  /* may not be right -- do this later */

#define LEAST_VALID       10 /* Don't trust a value lower than this */

int Read_timer()

{

  rtems_unsigned8 data;

  rtems_unsigned8  msb, osb, lsb;

  rtems_unsigned32 remaining, total;

  /* Disable timer so that timer can be read

        data = TCR;

        TCR = (data & 0xFE); */

  MC68230_READ (TCR, data);

  MC68230_WRITE (TCR, (data & 0xFE));

  /* Read the counter value

        msb = CNTRH;

        osb = CNTRM;

        lsb = CNTRL; */

  MC68230_READ (CNTRH, msb);

  MC68230_READ (CNTRM, osb);

  MC68230_READ (CNTRL, lsb);

  /* Calculate the time so far */

  remaining = 0x1000000 - ((msb << 16) + (osb << 8) + lsb);

  total = (Ttimer_val * 0x1000000) + remaining;

  /* Enable timer so that timer can continue

                TCR = 0xA1; */

  MC68230_WRITE (TCR, 0xA1);

  /* do not restore old vector */

  if ( Timer_driver_Find_average_overhead == 1 )

    return total;          /* in countdown units */

  if ( total < LEAST_VALID )

    return 0;            /* below timer resolution */

  /* Clocked at 6.5 Mhz */

  /* Avoid floating point problems, be lazy, and return the total minus

     the average overhead */

  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;

}