ID:176314 Can't place pin "<name>" at assigned pin location <name> (<name>) because location must feed a GXB transmitter PLL clock input port or a GXB receiver cruclk input port

CAUSE: The Fitter cannot place the pin at the specified location because the specified pin location must feed a gigabit transceiver block (GXB) transmitter PLL or GXB receiver PLL dedicated reference clock pin location.

ACTION: Delete the pin assignment.