定时器控制万历表时分秒

定时器控制显示万历表，为什么不能跳动啊？
#include <REGX51.H>
typedef unsigned int u16;
typedef unsigned char u8;
sbit LSA=P2^2;
sbit LSB=P2^3;
sbit LSC=P2^4;
u8 code smgduan[17]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f,0x77,0x7c,0x39,0x5e,0x79,0x71};
u8 hour=12,sec=57,min=59,num=0,i;
u8 DisplayData[8];

void delay(u16 i)
{
while(i--);
}

void Timer0() interrupt 1
{
TH0=(65536-55536)/256;
TL0=(65536-55536)%256;
num++;
}
void main()
{
TMOD=0X01;
TH0=(65536-55536)/256;
TL0=(65536-55536)%256;
ET0=1;
EA=1;
TR0=1;
for(i=0;i<8;i++)
{
switch(i)
{
case(0):
LSA=1;LSB=1;LSC=1;P0=smgduan[1]; break;//7
case(1):
LSA=0;LSB=1;LSC=1; P0=smgduan[hour%10];break;//6
case(2):
LSA=1;LSB=0;LSC=1;P0=0X40; break;//5
case(3):
LSA=0;LSB=0;LSC=1;P0=smgduan[min/10];break;//4
case(4):
LSA=1;LSB=1;LSC=0; P0=smgduan[min%10];break;//3
case(5):
LSA=0;LSB=1;LSC=0;P0=0X40; break;//2
case(6):
LSA=1;LSB=0;LSC=0; P0=smgduan[sec/10];break;//1
case(7):
LSA=0;LSB=0;LSC=0;P0=smgduan[sec%10]; break;//0
}

    delay(100); 
    P0=0x00;
}
if(num==100)  //1s
{
    sec++;
    num=0;
    if(sec>=60)
    {
    sec=0;
    min++;
      if(min>=60)
        {
             min=0;
              hour++;
             if(hour>=24)
              {
                hour=0;
        }
    }    
}    

}
}