设置中断优先级寄存器，当有外部中断0请求中断时，中断程序执行发光二极管程序，在此过程中，外部中断1也有中断请求，外部中断0的中断程序将被中断去执行外部中断1的中断程序（数码管加1显示程序）。

#include<reg51.h>
#define uchar unsigned char;
sbit key1=P3^2;
sbit key2=P3^3;
unsigned int i;
uchar led[]={0xfe,0xfd,0xfb,0xf7,0xef,0xdf,0xbf,0x7f};
uchar tube[]={0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90};

void delay1s(unsigned char time)
{
unsigned int i,j,k;
for(i=0;i<time;i++)
for(j=0;j<1000;j++)
for(k=0;k<144;k++);
}

int main(void)
{
IT0=1;
IT1=1;
EA=1;
EX0=1;
EX1=1;
PX0=1;
PX1=0;
while(1);
}
void int1(void) interrupt 0
{
while(!key1);
for(i=0;i<10;i++)
{
P1=0x00;
P2=tube[i];
delay1s(1);
}
}
void int2(void) interrupt 2
{
while(!key2);
for(i=0;i<8;i++)
{

	P0=led[i];delay1s(1);
}

}
视频：
https://www.bilibili.com/video/BV1jK411u7JH/