普中51单片机数码管实现9999到0的倒计时C语言

#include "reg51.h" //此文件中定义了单片机的一些特殊功能寄存器 typedef unsigned int u16; //对数据类型进行声明定义 typedef unsigned char u8; sbit LSA=P2^2; sbit LSB=P2^3; sbit LSC=P2^4; u16 flag=9999,num=0; u8 code smgduan[16]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07, 0x7f,0x6f,0x77,0x7c,0x39,0x5e,0x79,0x71};//显示0~F的值 void Timer0Init(void) //1毫秒@11.0592MHz { TMOD =0x01; //设置定时器模式 TL0 = 0x18; //设置定时初值 TH0 = 0xFC; //设置定时初值 TF0 = 0; //清除TF0标志 TR0 = 1; //定时器0开始计时 ET0 = 1; EA = 1; } void DIGdisplay() { u8 i; for (i=0;i<4;i++){ switch(i){ case(0): LSA = 1 ;LSB = 0 ; LSC = 0 ;P0 = smgduan[flag/10%10] ;break; //5 case(1): LSA = 0 ;LSB = 1 ; LSC = 0 ;P0 = smgduan[flag/100%10] ; break; //6 case(2): LSA = 1 ;LSB = 1 ; LSC = 0 ;P0 = smgduan[flag/1000] ; break; //7 第八个 case(3): LSA = 0 ;LSB = 0 ; LSC = 0 ;P0 = smgduan[flag%10] ;break; } P0 =0X00; } } void time() interrupt 1 { TL0 = 0x18; //设置定时初值 TH0 = 0xFC; //设置定时初值 num++; if(num==20) { num=0; flag--; } } void main() { Timer0Init(); P0 = 0x00; while(1) { DIGdisplay(); } }