时钟程序，显示的问题，有图求真相

时钟能正常走，就是有两个数字跟问号交替出现
下面是程序：
#include
#define uchar unsigned char
#define uint unsigned int
uchar code table[]=" 20  -  -       ";
uchar code table1[]="      :  :      ";
***it lcdrs=P2^0;  //1602信号
***it lcdrw=P2^1;  //写命令，置低电平
***it lcden=P2^2;  //1602使能端
***it dsrst=P2^5;  //ds1302复位
***it dsio=P2^6;   //1302IO口
***it dssck=P2^7;  //1302时钟
***it fmq=P3^5;    //蜂鸣器
***it s0=P3^0;     //增大键
***it s1=P3^1;     //减小键
***it s2=P3^2;     //功能键
***it s3=P3^3;     //闹钟查看键
bit run;
uchar miao, fen, shi, week, day, month, year, tflag;

void delayms(uint z)
{
uint x, y;
for(x=z;x>0;x--)
  for(y=110;y>0;y--);

}
void di()
{//蜂鸣器
fmq=0;
delayms(100);
fmq=1;
}

void write_com(uchar com)
{
lcdrs=0;
P0=com;
delayms(5);
lcden=1;
delayms(5);
lcden=0;
}
void write_data(uchar dat)
{
lcdrs=1;
P0=dat;
delayms(5);
lcden=1;
delayms(5);
lcden=0;
}
void write_sfm(uchar add,uchar date)
{//1602刷新时间
uchar shi,ge;
shi=date/16;
ge=date%16;
write_com(0x80+0x40+add);
write_data(0x30+shi);
write_data(0x30+ge);
}
void write_nyr(uchar add,uchar date)
{//1602刷新年月日
uchar shi,ge;
shi=date/16;
ge=date%16;
write_com(0x80+add);
write_data(0x30+shi);//0x30对应ASCII码
write_data(0x30+ge);
}
void write_week(char we)
{//星期
write_com(0x80+12);
switch(we)
{
  case 1: write_data('M');delayms(5);
    write_data('O');delayms(5);
    write_data('N');delayms(5);
    break;
  case 2: write_data('T');delayms(5);
    write_data('U');delayms(5);
    write_data('E');delayms(5);
    break;
  case 3: write_data('W');delayms(5);
    write_data('E');delayms(5);
    write_data('D');delayms(5);
    break;
  case 4: write_data('T');delayms(5);
    write_data('H');delayms(5);
    write_data('U');delayms(5);
    break;
  case 5: write_data('F');delayms(5);
    write_data('R');delayms(5);
    write_data('T');delayms(5);
    break;
  case 6: write_data('S');delayms(5);
    write_data('A');delayms(5);
    write_data('T');delayms(5);
    break;
  case 7: write_data('S');delayms(5);
    write_data('U');delayms(5);
    write_data('N');delayms(5);
    break;
}
}
void init1()
{
uchar num;
/*.........液晶初始程序................................*/
lcdrw=0;
lcden=0;
write_com(0x38);
write_com(0x0c);
write_com(0x06);
write_com(0x01);
write_com(0x80);
for(num=0;num<16;num++)
  write_data(table[num]);
write_com(0x80+0x40);
for(num=0;num<16;num++)
  write_data(table1[num]);
/*......................................................*/
}
void delayus(uint t)
{
t--;
}
/*................1302读写程序..........................*/
void write_byte(uchar dat)
{
uchar i;
dssck=0;//初始时钟线为0
for(i=0;i<8;i++)//开始传送八位字节的数据
{
  dssck=0;
  dsio=dat&0x01;//取最低位传送给IO
  delayus(2);
  dssck=1;//时钟线拉高，数据传走
  delayus(2);
  dssck=0;  
  dat>>=1;//右移一位
}
}
void write_ds(uchar add, uchar dat)
{
dsrst=0;//CE线为0
dssck=0;//时钟线为0
dsrst=1;//CE线为1，传输开始。。。位传输
write_byte(add);//传入命令字，写入时间，日历地址
write_byte(dat);//写入要修改的时间日历
dssck=1;//时钟线拉高
dsrst=0;//读取结束
}
uchar read_byte()
{
uchar i, dat;
delayus(2);
for(i=0;i<8;i++)
{
  dssck=0;
  dat>>=1;//左移一位
  if(dsio)
   dat|=0x80;//按位或，最高位成为1
  delayus(2);
  dssck=1;
  delayus(2);
  dssck=0;
}
return dat;//返回读取的值
}
uchar read_ds(uchar add)
{
uchar dat;
dsrst=0;
dssck=0;
dsrst=1;
write_byte(add);//写入命令字，地址
dat=read_byte();//读取数据
delayus(2);
dssck=1;
delayus(2);
dsrst=0;
return dat;
}
/*......................................................*/
/*void init2()//1302 初始化
{
write_ds(0x8e,0x00);//写保护关
write_ds(0x80,0x11);
write_ds(0x82,0x11);
write_ds(0x84,0x11);
write_ds(0x86,0x11);//日11
write_ds(0x88,0x11);//月11
write_ds(0x8a,0x05);//星期5
write_ds(0x8c,0x11);//年11
write_ds(0x90,0x01);//充电?????
write_ds(0xc0,0xf0);
write_ds(0x8e,0x80);//写保护开
}*/

void main()
{
TMOD=0X02;      //设置定时器0为工作方式2
TH0=0X06;       //装初值
TL0=0X06;      
EA=1;          //开总中断
ET0=1;         //开定时器0中断
TR0=1;         //启动定时器0
init1();       //1602初始程序
// init2();    //1302初始程序
/* year=read_ds(0x8d);
write_nyr(3,year);
month=read_ds(0x89);
write_nyr(6,month);
day=read_ds(0x87);
write_nyr(9,day);
shi=read_ds(0x85);
write_sfm(4,shi);
fen=read_ds(0x83);
write_sfm(7,fen);
miao=read_ds(0x81);
write_sfm(10,miao);
week=read_ds(0x8b);
write_week(week);
*/

while(1)
{   
  delayms(20);
  miao=read_ds(0x81);  
  fen=read_ds(0x83);
  shi=read_ds(0x85);
  year=read_ds(0x8d);
  month=read_ds(0x89);
  day=read_ds(0x87);
  week=read_ds(0x8b);
  write_sfm(10,miao);
  write_sfm(7,fen);
  write_sfm(4,shi);
  write_nyr(3,year);
  write_nyr(6,month);
  write_nyr(9,day);
  write_week(week);
}

}
void timer02()interrupt 1
{
/* tflag++;
if(tflag==4000)
{
  run=1;
  tflag=0;
}
*/
}