此程序的電路圖下載：http://www.denmoz.com/f/ks51.pdf 只需要看數碼管部分即可，其他部分可忽略掉.
#include <reg52.h>
typedef unsigned char uchar;
typedef unsigned int uint;
typedef unsigned long ulong;
sbit ENLED = P1^4;
sbit ADDR0 = P1^0;
sbit ADDR1 = P1^1;
sbit ADDR2 = P1^2;
sbit ADDR3 = P1^3;
uchar led_char[] = {
0xC0, 0xF9, 0xA4, 0xB0,
0x99, 0x92, 0x82, 0xF8,
0x80, 0x90, 0x88, 0x83,
0xC6, 0xA1, 0x86, 0x8E};
uchar led_buf[] = {0xFF,0xFF,0xFF,0xFF,0xFF,0xFF};
uchar cnt = 0;
uchar key = 0;
ulong sec = 0;
void main()
{
EA = 1;
ENLED = 0;
ADDR3 = 1;
TMOD = 0x10;
TH1 = 0xEE;
TL1 = 0x00;
ET1 = 1;
TR1 = 1;
while(1)
{
if(200 == cnt)
{
cnt = 0;
sec++;
led_buf[0] = led_char[sec%10];
led_buf[1] = led_char[sec/10%10];
led_buf[2] = led_char[sec/100%10];
led_buf[3] = led_char[sec/1000%10];
led_buf[4] = led_char[sec/10000%10];
led_buf[5] = led_char[sec/100000%10];
}
}
}
void interruptTimer0() interrupt 3
{
TH1 = 0xEE;
TL1 = 0x00;
cnt++;
P0 = 0xFF;
switch(key)
{
case 0: ADDR2 = 0;ADDR1 = 0;ADDR0 = 0;P0 = led_buf[0];key++;break;
case 1: ADDR2 = 0;ADDR1 = 0;ADDR0 = 1;if(sec>9) P0 = led_buf[1];key++;break;
case 2: ADDR2 = 0;ADDR1 = 1;ADDR0 = 0;if(sec>99) P0 = led_buf[2];key++;break;
case 3: ADDR2 = 0;ADDR1 = 1;ADDR0 = 1;if(sec>999) P0 = led_buf[3];key++;break;
case 4: ADDR2 = 1;ADDR1 = 0;ADDR0 = 0;if(sec>9999) P0 = led_buf[4];key++;break;
case 5: ADDR2 = 1;ADDR1 = 0;ADDR0 = 1;if(sec>99999) P0 = led_buf[5];key = 0;break;
default:break;
}
}