for (i=0x04;i;i>  >  =1) {

          KBD_PORT=(KBD_PORT&0xC0) | 0x38 | ((~i)&0x07);//读端口锁存器??????
                                                     
                                                       

  k=KBD_PORT&0x38;//读引脚????????

  if (k==0x38) continue;
  return k|i;
 }
 return KEY_NULL;
}
怎么区分是读引脚还是读端口锁存器?我晕!!!!!!!!!! 

                                                                  一个初学者