数码管动态显示定时器中断数码管动态显示不正常

单片机

下面是郭天祥老师《新概念51单片机C语言教程》75页的程序，我想用proteus 仿真，
按照书上的延时5毫秒仿真，数码管显示数字不完整，附图是仿真结果，什么原因？
哪位朋友给解释一下。

#include
#define uchar unsigned char
#define uint unsigned int
***it dula=P2^6;
***it wela=P2^7;
***it led1=P1^0;
uchar code table[]={
0x3f,0x06,0x5b,0x4f,
0x66,0x6d,0x7d,0x07,
0x7f,0x6f,0x77,0x7c,
0x39,0x5e,0x79,0x71};
void delayms(uint);
void display(uchar,uchar);
uchar num,num1,num2,shi,ge;
void main()
{
TMOD=0x11;
TH0=(65536-45872)/256;
TL0=(65536-45872)%256;
TH1=(65536-45872)/256;
TL1=(65536-45872)%256;
EA=1;
ET0=1;
ET1=1;
TR0=1;
TR1=1;
while(1)
{
   display(shi,ge);
}
}

void display(uchar shi,uchar ge)
{

  dula=1;
  P0=table[shi];
  dula=0;
  P0=0xff;
  wela=1;
  P0=0xfe;
  wela=0;
  delayms(500);

  dula=1;
  P0=table[ge];
  dula=0;
  P0=0xff;
  wela=1;
  P0=0xfd;
  wela=0;
  delayms(500);

}

void delayms(uint xms)
{
uint i,j;
for(i=xms;i>0;i--)
   for(j=110;j>0;j--);
}

void T0_time() interrupt 1
{
TH0=(65536-45872)/256;
TL0=(65536-45872)%256;
num1++;
if(num1==4)
{
   num1=0;
   led1=~led1;
}
}

void T1_time() interrupt 3
{
TH1=(65536-45872)/256;
TL1=(65536-45872)%256;
num2++;
if(num2==20)
{
   num2=0;
   num++;
   if(num==60)
      num=0;
   shi=num/10;
   ge=num%10;
}
}