Description
Due to mistakes in "Table 9-12: Avalon-ST TX Interface Signals" and "Table 11-8: Avalon-ST TX Interface" of the Altera® Transceiver PHY IP Core User Guide (PDF) the tx_datak signal refers to received data for the Arria® V, Cyclone® V and Stratix® V devices.
The tx_datak signal should only refer to the transmit data.
Resolution
These problems will be fixed in a future version of the Altera Transceiver PHY IP Core User Guide (PDF).