Proteus 仿真电路图：

C51代码：

#include<reg51.h>typedef unsigned char uchar;
typedef unsigned int uint;uchar code num[10]={0xC0, 0xF9, 0xA4, 0xB0, 0x99, 0x92, 0x82, 0xF8, 0x80, 0x90};  // 0~9字码uchar miao=0, fen=0, shi=0;  //进位标志位uint i=0;  //计时uchar miao_L, miao_H, fen_L, fen_H, shi_L, shi_H;  //时、分、秒的个位（xxx_L）和十位（xxx_H）  void delay(uint x){  //延时函数 while(x--);
}void T0_init(){                     //定时器 0 初始化 TMOD = 0x01; //工作方式 1TH0 = 0x3c;  //高八位赋初值    65536-50000=15536 = 3cb0HTL0 = 0xb0;	 //底八位赋初值EA = 1;	     //开总中断ET0 = 1;     //开 T0 中断TR0 = 1;     //启动 T0
}void display(){  //显示P2 = 0x20;  //秒与分间隔线P0 = 0xbf;	delay(500);P2 = 0x04;  //分与时间隔线P0 = 0xbf;delay(500);P2 = 0x80;  //数码管位选 1000 0000P0 = num[miao_L];  //秒个位delay(500);P2 = 0x40;	//数码管位选 0100 0000P0 = num[miao_H];  //秒十位delay(500);P2 = 0x10;	//数码管位选 0001 0000P0 = num[fen_L];  //分个位delay(500);P2 = 0x08;	//数码管位选 0000 1000P0 = num[fen_H];  //分十位delay(500);P2 = 0x02;	//数码管位选 0000 0010P0 = num[shi_L];  //分个位delay(500);P2 = 0x01;	//数码管位选 0000 0001P0 = num[shi_H];  //分十位delay(500);}void main(){T0_init();  //定时器初始化while(1){display();  //显示		}}void timer0_int() interrupt 1{  //中断服务函数i++;if(i == 20){i = 0;  //满一秒清零miao++;	//i = 100 为一，秒标志位加 1if(miao == 60){miao = 0;  //满一分清零fen++;if(fen == 60){fen = 0;  //满一时清零shi++;if(shi == 24){shi = 0;  //24小时制fen = 0;miao = 0;}}}miao_L = miao%10;  //秒个位miao_H = miao/10;  //秒十位fen_L = fen%10;  //分个位fen_H = fen/10;  //分十位shi_L = shi%10;  //时个位shi_H = shi/10;  //时十位}}

按键实现日期可调的转这篇

基于51单片机的数码管时钟设计——按键修改时间