timer.c

用于汇编领域的,运用于OS的MAIN函数.基于硬件基础的源代码

#include "hos.h"

void timer_isr(void);

unsigned long systick;

void timer_handler(void)
{
	systick++;
	// decrease counter of current
	current->counter--;
	if (!current->counter){// switch
		current->counter=INIT_COUNTER; // restore it
		/*
		current=next_p(); // select next process
		// change stack
		__asm__("movl %0, %%esp\n\t"
			: : "m"(current->esp));
			*/
		current->need_reschedule=1;
	}

	outbyte(0x20, 0x20);	/* EOI to Master */
	outbyte(0xA0, 0x20);	/* EOI to Slave */
}

void init_timer(void)
{
	int temp = 1193180 / HZ;

	outbyte(MODECTRL, S_CNTR0 | RWLSB_MSB | TIMER_MODE3);
	outbyte(TIMER_PORT0, (temp & 0xFF));
	outbyte(TIMER_PORT0, ((temp >> 8) & 0xFF));

	systick = 0;

	set_intr_gate(0x20, &timer_isr);

	unmask_irq(0);
}

void delay(int TenMillisecond){
   int before = systick;
   int after;

   while(1){
      after = systick;
	  if (before > after){
	     before = systick;
		 continue;
	  }
	  if ((before+TenMillisecond)==after)
	     break;
  }
}