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/* Timer_init()
*
* This routine initializes a timer in efi68k's DP8570A TCP
*
* Input parameters: NONE
*
* Output parameters: NONE
*
* NOTE: It is important that the timer start/stop overhead be
* determined when porting or modifying this code.
*
* COPYRIGHT (c) 1989-1998.
* On-Line Applications Research Corporation (OAR).
* Copyright assigned to U.S. Government, 1994.
*
* 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.
*
* $Id$
*/
#include <bsp.h>
rtems_boolean Timer_driver_Find_average_overhead;
extern rtems_isr Clock_isr();
void Timer_initialize( void )
{
/* stop counter */
*MSR = 0;
*T0CR = 0;
/*
* Make sure isr is installed
*/
set_vector( Clock_isr, TCP_ISR_LEVEL+24, 1);
/* clear timer ISR count */
Timer_interrupts = 0;
/* load count (count down timer) */
*MSR = 0;
*T0_MSB = 0xff;
*T0_LSB = 0xff;
/* clear old interrupts */
*MSR = T0;
/* enable timer 0 interrupt */
*MSR = RS;
*ICR0 |= T0E;
/*
TSS = 1 starts the timer (timer resets on start)
M1/0 = 0/1 rate generator
C2/1/0 = 0/0/0 external clock (8MHz) (1/8 usec resolution)
RD = 0 read data (latchs count)
CHG = 0 hold
*/
*MSR = 0;
*T0CR = (TSS | M0);
}
/*
* The following controls the behavior of Read_timer().
*
* 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 Read_timer( void )
{
rtems_unsigned16 clicks;
rtems_unsigned32 total;
rtems_unsigned32 msb, lsb;
/*
* Read the timer and see how many clicks it has been since counter
* rolled over.
*/
*MSR = 0;
*T0CR |= RD;
/* must read MSB first */
msb = *T0_MSB;
lsb = *T0_LSB;
clicks = 0xffff - ((msb << 8) | lsb);
/*
* 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 * 0x10000 + clicks + 4)/8; /* in micoseconds */
/* ^^^ round to nearest int */
if ( Timer_driver_Find_average_overhead == 1 )
return total; /* in XXX microsecond units */
if ( total < LEAST_VALID )
return 0; /* below timer resolution */
return (total - AVG_OVERHEAD);
}
/*
* Empty function call used in loops to measure basic cost of looping
* in Timing Test Suite.
*/
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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