设计一个9秒倒计时，数码管从9每秒减一，到0后定时关，蜂鸣器响。

#include<reg51.h>

sbit wela=P2^7;

sbit dula=P2^6;

unsigned char i=0;

unsigned char code table[]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f};

void delay(int xms)

{

int o,u;

 for(o=xms;o>0;o--)  

 for(u=110;u>0;u--);

}

void main()

{

unsigned char num;num=9;

TMOD=0x10;

TH1=(65536-50000)/256;

TL1=(65536-50000)%256;

TR1=1;

EA=1;

ET1=1;

while(1)

{

dula=0;wela=0;

dula=1;P0=table[num];dula=0;P0=0xff;delay(20);

wela=1;P0=0xfe;wela=0;

if(i==20)

{

num--;i=0;

}

if(num==0)

{

TR1=0;

}}

}

void timeee () interrupt 3

{

TH1=(65536-50000)/256;

TL1=(65536-50000)%256;

i++;

}

---课程作业