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/*
*
* This routine initializes TIMER 2 for an MC68302.
*
* 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.
*
* $Id$
*/
#include <rtems.h>
#include <bsp.h>
#include <rtems/m68k/m68302.h>
#define TMR2_VAL 0x071b /* Timer mode register
* (section 3.5.2.1 in 68302 manual)
* 15-8: "7" prescaler divide by 8 (x+1)
* 7-6: 00 dis. intr. on capture event
* 5: 0 active-low pulse
* 4: 1 intr. on reaching reference
* 3: 1 restart counter on reference
* 2-1: 01 master clock input source
* 0: 1 enable timer
*/
#define TRR2_VAL 2000 /* Timer reference register
* (section 3.5.2.2 in 68302 manual)
* 2000 ticks @ (16MHz/1)/8 = 1-ms count
*/
uint32_t Timer_interrupts;
bool benchmark_timer_find_average_overhead;
rtems_isr timerisr(void);
void benchmark_timer_initialize( void )
{
m302.reg.tmr2 = 0; /* disable timer */
Timer_interrupts = 0; /* clear timer ISR count */
m302.reg.trr2 = TRR2_VAL; /* set timer reference register */
m302.reg.tmr2 = TMR2_VAL; /* set timer mode register */
m302.reg.imr |= RBIT_IMR_TIMER2; /* set 68302 int-mask to allow ints */
}
/*
* The following controls the behavior of benchmark_timer_read().
*
* FIND_AVG_OVERHEAD * instructs the routine to return the "raw" count.
*
* AVG_OVEREHAD is the overhead for starting and stopping the timer. It
* is usually deducted from the number returned.
*
* LEAST_VALID is the lowest number this routine should trust. Numbers
* below this are "noise" and zero is returned.
*/
#define AVG_OVERHEAD 0 /* It typically takes X.X microseconds */
/* (Y countdowns) to start/stop the timer. */
/* This value is in microseconds. */
#define LEAST_VALID 1 /* Don't trust a clicks value lower than this */
/*
* Return timer value in 1/2-microsecond units
*/
int benchmark_timer_read( void )
{
uint16_t clicks;
uint32_t total;
/*
* Read the timer and see how many clicks it has been since counter
* rolled over.
*/
clicks = m302.reg.tcn2;
/*
* Total is calculated by taking into account the number of timer overflow
* interrupts since the timer was initialized and clicks since the last
* interrupts.
*/
total = (Timer_interrupts * TRR2_VAL) + clicks;
if ( benchmark_timer_find_average_overhead == true )
return total; /* in XXX microsecond units */
if ( total < LEAST_VALID )
return 0; /* below timer resolution */
/*
* Convert 1/2-microsecond count into microseconds
*/
return (total - AVG_OVERHEAD) >> 1;
}
void benchmark_timer_disable_subtracting_average_overhead(
bool find_flag
)
{
benchmark_timer_find_average_overhead = find_flag;
}
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