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/* Timer_init()
*
* This routine initializes the timer on the FORCE CPU-386 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 Z8036
* 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.
*
* $Id$
*/
#include <rtems.h>
#include <bsp.h>
int Ttimer_val;
rtems_boolean Timer_driver_Find_average_overhead;
rtems_isr timerisr();
#define TMR0 0xF040
#define TMR1 0xF041
#define TMR2 0xF042
#define TMRCON 0xF043
#define TMRCFG 0xF834
void Timer_initialize()
{
(void) set_vector( timerisr, 0x2a, 0 ); /* install ISR ( IR2 ) was 0x38*/
Ttimer_val = 0; /* clear timer ISR count */
outport_byte ( TMRCON , 0xb0 ); /* select tmr2, stay in mode 0 */
outport_byte ( TMR1 , 0xd2 ); /* set to 250 usec interval */
outport_byte ( TMR1 , 0x00 );
outport_byte ( TMRCON , 0x64 ); /* change to mode 2 ( starts timer ) */
/* interrupts ARE enabled */
/* outport_byte( IERA, 0x41 ); enable interrupt */
}
#define AVG_OVERHEAD 3 /* It typically takes 3.0 microseconds */
/* (3 ticks) to start/stop the timer. */
#define LEAST_VALID 4 /* Don't trust a value lower than this */
int Read_timer()
{
register rtems_unsigned32 clicks;
register rtems_unsigned32 total;
/* outport_byte( TBCR, 0x00 ); stop the timer -- not needed on intel */
outport_byte ( TMRCON, 0x40 ); /* latch the count */
inport_byte ( TMR1, clicks ); /* read the count */
total = Ttimer_val + 250 - clicks;
/* outport_byte( TBCR, 0x00 ); initial value */
/* outport_byte( IERA, 0x40 ); disable interrupt */
/* ??? Is "do not restore old vector" causing problems? */
if ( Timer_driver_Find_average_overhead == 1 )
return total; /* in one microsecond units */
else {
if ( total < LEAST_VALID )
return 0; /* below timer resolution */
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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