读中断寄存器，高手们，来看看

用AT89C52+D12
A接高，WR，RD，ALE，D0-7互接
读中断寄存器读不出来数据，都是0怎么回事，高手们，来看看
unsigned short D12_ReadInterruptRegister(void)
{
unsigned char b1;
unsigned int j;
//outportb(D12_COMMAND, 0xF4);
outportcmd(0xF4);
b1 = inportb();
j = inportb();
j <<= 8;
j += b1;
return j;
}

D12_DATA=0xff02;
D12_COMMAND=0xff03;
void outportcmd(unsigned char value)
{
*((unsigned char xdata *)D12_COMMAND)=value
}
void outportdata(unsigned char value)
{
   *((unsigned char xdata *)D12_DATA)=value;
}

unsigned char inportb(void)
{
 return *((unsigned xdata *)D12_DATA);
}

[编辑 -  1/7/04 by  yyouking]

#define D12_COMMAND (*(unsigned char xdata *)0xff03)
#define D12_DATA (*(unsigned char xdata *)0xff02)

void outportcmd(unsigned char value)
{
D12_COMMAND=value;
}
void outportdata(unsigned char value)
{
D12_DATA=value;
}

unsigned char inportb(void)
{
return D12_DATA;
}