我用C编了一个单片机数码管显示程序。大意是数码管前面三个每秒显示HOO,RRE，YOU；后面三个从999每秒递减到0，如此循环下去。
    但是6个数码管中，只有最后一个显示个位的循环显示9-0。
    源程序如下.
 #include<reg52.h>
#define uchar unsigned char
#define uint  unsigned int
sbit dula=P2^6;
sbit wela=P2^7;
uchar code table[]={
        0x3f,0x06,0x5b,0x4f,
        0x66,0x6d,0x7d,0x07,
        0x7f,0x6f,0x77,0x7c,
        0x39,0x5e,0x79,0x71,
        0x76,0x79,0x38,0x3f,0
                   }; 
uchar code word1[]={
        0x76,0x77,0x6e
                    };
uchar code word2[]={
        0x3f,0x77,0x3f
                    };
uchar code word3[]={
       0x3f,0x79,0x3e
                    };
uchar tt,bai,shi,ge,num;
uint  count;
void init();
void display();
void delay(uchar);
void main ()
{
    init();
    while(1)
    {
        if(tt==20)
        {
           tt=0;
           bai=count/100;
           shi=count%100/10;
           ge=count%10;
           count--;
           if(count==0)
            count=999;
           display();

        }
    }        
}
void init()
{
    num=0;
    count=999;
    tt=0;
    TMOD=0x01;
    TH0=(65536-50000)/256;
    TL0=(65536-50000)%256;
    EA=1;
    ET0=1;
    TR0=1;//启T0计数
}
void display()
{
    if(num==3)
     num=0;
     
    dula=1;
    P0=word1[num];
    dula=0;
    P0=0xff;  //消隐
    wela=1;
    P0=0xfe;
    wela=0;
    delay(1);

    dula=1;
    P0=word2[num];
    dula=0;
    P0=0xff;  //消隐
    wela=1;
    P0=0xfd;
    wela=0;
    delay(1);

    dula=1;
    P0=word3[num];
    dula=0;
    P0=0xff;  //消隐
    wela=1;
    P0=0xfb;
    wela=0;
    delay(1);

    num++;

    dula=1;
    P0=table[bai];
    dula=0;
    P0=0xff;  //消隐
    wela=1;
    P0=0xf7;
    wela=0;
    delay(1);

    dula=1;
    P0=table[shi];
    dula=0;
    P0=0xff;  //消隐
    wela=1;
    P0=0xef;
    wela=0;
    delay(1);

    dula=1;
    P0=table[ge];
    dula=0;
    P0=0xff;  //消隐
    wela=1;
    P0=0xdf;
    wela=0;
    delay(1);
            
}
void delay(uchar z)
{
    uchar x,y;
    for (x=z;x>0;x--)
     for(y=100;y>0;y--);
}
void timer0 () interrupt 1
{
    TMOD=0x01;
    TH0=(65536-50000)/256;
    TL0=(65536-50000)%256;
    EA=1;
    ET0=1;
    TR0=1;
    tt++;    
}
求大侠帮忙解决啊