51单片机怎么通过8155，让数码管显示

我想通过8155扩展芯片，让数码管显示，一直弄不出来，各位看看有什么问题
#include <reg52.h>
#include<absacc.h>
#define unit unsigned int
#define uchar unsigned char
#define COM XBYTE[0x7f00]
#define PA  XBYTE[0x7f01]
#define PB  XBYTE[0x7f02]
#define PC  XBYTE[0x7f03]
sbit IO = P2^3;
unsigned char code table_seg[]={
           0xc0,0xf9,0xa4,0xb0,
     0x99,0x92,0x82,0xf8,
     0x80,0x98,0xa0,0x83,
     0xa7,0xa1,0x86,0x8e,
           0xff               };
unsigned char code table_bit[]={
           0x01,0x02,0x04,0x08,
     0x10,0x20,0x40,0x80
   
                            };
void delay ( unsigned int num,x,y)
{
   
    for (x=num; x>0;x--)
    for (y=110; y>0; y--)
    {
    ;
    }
}
void main (void)
{
      IO = 1 ;
      COM = 0x0c;
   while(1)
   {
     P0 = 0x01;
     PB = table_bit[1];
   
     PA = table_seg[1];
     delay(500);
   
   }
}

51上P2^3接8155的IO/M,P2^7接CE；
8155的PA作为段选，PB作为位选

大神们，快点出现吧