PADS I/O Designer checks for assignments to differential pins, i.e., pairs of pins that should be assigned to one signal, representing its positive and negative part, respectively. Differential pins are by default treated as normal. For any differential pin it is possible to turn on the differential pins support built in PADS I/O Designer. To do that, switch the type of such pin to DIFF. Then the type of the second pin of the pair will be switched to DIFF too. Similarly as for clock signals, a signal may be marked as being differential. Such signals are to be assigned to differential pin pairs.
To mark a signal as differential, locate it in the Signals List, click in the Type column, and in the displayed list select the DIFF option.
To unmark a signal as differential, locate it in the Signals List, click in the Type column and, in the displayed list, select the IO option. Then, whenever a signal is assigned to one pin of the pair, the other pin is assigned to the same signal automatically.
You can also choose as the type of a signal DIFFCLOCK, which means that such a signal is both a clock and a differential signal.
To easily distinguish differential pins, right-click on the Pins List and select Combine All Differential Pins. Two-element bus pins are created from all differential pin pairs. If one of a pair of differential pins is selected, right-click on the Pins List and select Goto Complementary Differential Pin to locate another one from the pair.