XC4010XL : parallel port access through data pin

Hi, I try to send bits to my xc4010XL FPGA through a parallel cable but I encounter problems... I've got LED conected to the right pin (they are working fine because I have already tested them with an other program). Well, i use a program to change the parallel cable pin value (work fine too because i controlled each pin with a multimeter). When i use the special pin MD0 and MD2 it work fine (i can display the value on the led) but whenever i try use acquire the data through the data pin (P45 to P49) it does not work... Did I forget a special component, configuration? I tryed with IBUF.. thank you for helping me