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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, 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.
*
* $Id$
*/
#include "rtems.h"
#include "cpu.h"
#include "bsp.h"
#include "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;
}
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