timer_o.c

来自「TIMER OF FRESCALE MICRO」· C语言 代码 · 共 80 行

/* Copyright 1999 Delphi Delco Electronics Systems */
/*
 * Purpose: to implement a timer overflow counter for CAPCOM1 timer 0
 *
 * Author: kingdj
 * Date: Wed Nov 19 15:53:17 EST 1997
 * $Header: timer_o.c,v 1.2 98/06/02 11:34:07 kingdj Exp $
 */

/* include files */

#include "interrupt.h"
#include "io.h"
#include "timer_o.h"


/* constants and macros */



/* type definitions */



/* global variables - initialize here */



/* local variables - use static */

LOCAL_DATA overflow_timer;

/* private function prototypes - use static */



/* function definitions */

/* Purpose: To handle the overflow of Timer 0.
 *
 * Parameters: none
 */
/*@unused@*/
LOCAL_FUNC interrupt (T0_TRAP_NUM) void Timer_Overflow(void)
{
  /* IR is cleared automatically when ISR executes */
  overflow_timer++;
}

/* Purpose: To report the (adjusted) timer overflow count
 *
 *    The count is adjusted upward if the overflow has occurred since
 *    the time of the passed in pulse
 *
 * Parameters:
 *
 * input_time - the captured time
 */
EXPORT_FUNC unsigned WORD Overflow_Adjustment( unsigned WORD input_time )
{
  if ( (input_time < 0x8000) && (T0IR) )
    {
      /* Add one more count to overflow timer if timer overflow interrupt
       * is pending but not yet serviced.  The "not yet serviced" condition
       * is determined by a low input time (less than half of 16 bits) with
       * the interrupt request bit set. */
      return overflow_timer + 1;
    }
  else
    {
      return overflow_timer;
    }
}

/*
 * $SOURCE: [e-mail]:01_a4_beetle_ip:timer_o.c $
 * $REVISION: 1.4 $
 * $AUTHOR: flint.iac:/users/wileyeg/dsds/vwnewhw:wileyeg $
 */