Question

若51单片机P1口接了8个LED,编写程序完成跑马灯程序要求大约1秒变化一次

单片机编程题

Answer 1

//假设晶振12MHZ，P1控制8个LED低电平亮
#include "reg51.h"
unsigned int YSJS=0;
signed char LED=0XFE;
void main(void)
{
TMOD |= 0X10; //定时器1工作于方式1,16位定时器
TH1 = 0XFE; //定时器1定时时间=500uS
TL1 = 0X0C;
ET1 = 1; //使能定时器1中断
TR1 =1;
EA =1; //开总中断

while(1)
{
}
}

void TIMER1(void) interrupt 3 //定时器1中断函数使用默认寄存器组
{
TH1 = 0XFE; //定时器1定时时间=500us
TL1 = 0X0C;

YSJS++;
if(YSJS==2000) //500uS*2000=1000000uS=1S
{
P1 = LED;
LED=LED<<1;
LED=LED | 1
if(LED==0XFF)LED=0XFE;
YSJS = 0
}
}