51单片机c语言，数码管计时，只显有效位（消隐）

#include<reg52.h>
sbit ADDR0=P1^0;
sbit ADDR1=P1^1;
sbit ADDR2=P1^2;
sbit ADDR3=P1^3;
sbit ENLED=P1^4;
unsigned char code LedChar[]={
     0xC0,0xF9,0xA4,0xB0,0x99,0x92,0x82,0xF8,0x80,0x90,0x88,0x83,0xC6,0xA1,0x86,0x8E
};
unsigned char LedBuff[6]={
     0xFF,0xFF,0xFF,0xFF,0xFF,0xFF
};

    unsigned char i=0;
    unsigned int   cnt=0;
    unsigned char flag1s=0;
        unsigned long sec=0;
void main()
{

    EA=1;
    ENLED=0;
    ADDR3=1;
    TMOD=0x01;
    TH0=0xFC;
    TL0=0x67;
    ET0=1;
    TR0=1;

    while (1)
    {
      if (flag1s==1)
      {
    &nb