timer.c

这是《Keil Cx51 V7.0单片机高级语言编程与uVision2应用实践》教材各章中列出的全部程序例子。

#include "tdp.h"
#include <reg51.h>
#define TIMER0_COUNT	 0xDC11	 /* 10000h-((11059200Hz/(12*FREQ))-17) */

static xdata unsigned timer0_tick;

/* 定时器T0中断服务函数 */
static void timer0_isr (void) interrupt 1 using 1  {
		P1 |= 0x80;
		TR0 = 0;				    /* 停止 T0 */
		TL0 = TL0 + (TIMER0_COUNT & 0x00FF);
		TH0 = TH0 + (TIMER0_COUNT >> 8);
		TR0 = 1;		     		/* 启动T0 */		
		timer0_tick++;		
		P1 &= ~0x80;
	}

/* 定时器T0初始化函数 */
void timer0_initialize (void) {
	INT_DISABLE;			/* 关中断 */	
	timer0_tick = 0;
	TR0 = 0;			    /* 停止T0 */	
	TMOD &= ~0x0F;		/* 设置T0工作方式 */
	TMOD |= 0x01;			
	TL0 = (TIMER0_COUNT & 0x00FF);
	TH0 = (TIMER0_COUNT >> 8);	
	PT0 = 0;				/* 设置T0中断优先级 */
	ET0 = 1;				/* 允许T0中断 */	
	TR0 = 1;				/* 启动T0 */	
	INT_ENABLE;			/* 开中断 */
}

/* 定时器T0节拍函数 */
unsigned timer0_count (void) {
	xdata unsigned t;
	INT_DISABLE;
	t = timer0_tick;
	INT_ENABLE;	
	return (t);
}

/* 定时器T0节拍计数函数 */
unsigned timer0_elapsed_count (unsigned count) {
	return (timer0_count () - count);
}

/*  定时器T0延时函数  */
void timer0_wait (unsigned count) {
	xdata unsigned start_count;
	start_count = timer0_count ();	
	while (timer0_elapsed_count (start_count) <= count)
	  {
	  }
}