View \TIMER.CPP

C++ sources for serial communication

Submitted By: WEBMASTER
Rating:

(Rate It)

File Details

ZIP File Browser

// Copyright ***********************************************************
//
// The information in this file is copyright 1991 by David Orme.
//
// Anyone may use this information for any purpose as long as he takes
// responsability for any and all libility incurred from its use
// or misuse and acknowledges its use in the user documentation. This
// information is provided AS IS with no warrenty of any kind, either
// expressed or implied.
//
// End *****************************************************************

// Contents ************************************************************
//
// Timer::Timer()
// Timer::~Timer()
// Timer::NewTimer()
//
// Description
//
// The Timer class implements a hardware-based background timer.
// Note that all instances of this class reference the _same_ timer
// ISR.
//
// End *****************************************************************

// Interface Dependencies ----------------------------------------------

#ifndef __TIMER_H
#include "timer.h"
#endif

// Implementation Dependencies -----------------------------------------

#ifndef __DOS_H
#include <dos.h>
#define __DOS_H
#endif

// Global Variables ----------------------------------------------------

volatile unsigned long Timer::ticker = 0l;
void interrupt (far * Timer::oldtimer)(...) = 0;

// Constructor //

Timer::Timer()

// Summary -------------------------------------------------------------
//
// Initialize the new timer interrupt handler
//
// End -----------------------------------------------------------------

{
ticker = 0l;
oldtimer = getvect(TIMER);
setvect(TIMER, Timer::NewTimer);
}

// Destructor //

Timer::~Timer()

// Summary --------------------------------------------------------------
//
// Restore the old timer interrupt in the chain
//
// End ------------------------------------------------------------------

{
setvect(TIMER, oldtimer);
}

// ISR //

void interrupt far Timer::NewTimer(...)

// Summary --------------------------------------------------------------
//
// After chaining to the old interrupt handler, decrement our
// counter if it is greater than 0.
//
// End ------------------------------------------------------------------

{
(*oldtimer)();
if (ticker > 0l)
--ticker;
}