www.pudn.com > tcpip5151.rar > Timer.c

//----------------------------------------------------------------------------- 
// Net TIMER.C 
// 
// This module sets up the timer and handles the timer interrupt 
//----------------------------------------------------------------------------- 
#include  
#include "net.h" 
#include "timer.h" 
 
 
extern UINT volatile event_word; 
extern ULONG idata initial_sequence_nr; 
 
 
//-------------------------------------------------------------------------- 
// Timer 2 interrupt service routing. Intr vector location is 
// address 0x002B. The timer generates an interrupt every 25 msec 
// It is set to auto reload so do not need to reload it. 
//-------------------------------------------------------------------------- 
void timer1_interrupt(void) interrupt 3 
{ 
	static UINT count1 = 0; 
	static UINT count2 = 0; 
	 
	TH1=0X4C; 
	TL1=0;	 
	// Advance the initial sequence number 
	initial_sequence_nr += 6250; 
   // Keep it some distance from rolling over 
   if (initial_sequence_nr & 0x10000000L) initial_sequence_nr = 1; 
	 
	count1++; 
	// These events happens every 0.50 seconds, not simultaneously 
	if (count1 == 5) event_word |= EVENT_ARP_RETRANSMIT; 
	 
	if (count1 == 10) event_word |= EVENT_TCP_INACTIVITY; 
	 
	if (count1 == 15) event_word |= EVENT_READ_ANALOG; 
	 
	if (count1 == 20) 
	{ 
	 	count1 = 0; 
	 	event_word |= EVENT_TCP_RETRANSMIT; 
	} 
	 
	count2++; 
	if (count2 == 2401) 
	{ 
		// This happens every 60.025 seconds, not simultaneous 
		// with above tasks 
		count2 = 0; 
		event_word |= EVENT_AGE_ARP_CACHE; 
	} 
}