ID:12342 Can't turn on open-drain option for differential I/O pin <name>

CAUSE: You turned on the open-drain option for the specified differential I/O pin. However, differential I/O pins must have the open-drain option turned off. You may have assigned the GTL or GTL+ I/O standard to the pin, which are open-drain I/O standards. As a result, the I/O pin has the open-drain option turned on by default. You may have later assigned a differential I/O standard to the same I/O pin.

ACTION: Assign only one I/O standard to the pin throughout the design.