When using large FPGA's on a PCB making sure that the FPGA pins are connected to the right signals on the PCB is a cumbersome task. On the FPGA side the pins are assigned to the HDL signals that form the toplevel of the logic implemented on the FPGA. On the PCB side the pins have to be connected to the proper net that will connect it to other components on the PCB. Because implementation of FPGA and PCB is often done in parallel and by different engineers, the signal names used are not always identical. To make things even worse, it is often necessary to perform pin swaps to prevent PCB routing problems. These pin swaps have to be made both on the FPGA and the PCB. As this is almost always manual work, and current devices have over 1500 pins, a mistake is easily made.