Description
Due to a mistake in "Table 2-40: TX Standard PCS: Data, Control, and Clocks" of the Arria® 10 device Transceiver PHY User Guide (PDF) the tx_datak signal is described as being '1' for a data word and '0' as a control word.
The tx_datak signal should be '0' for a data word and '1' for a control word.
Resolution
This problem will be fixed in a future version of the Arria 10 Transceiver PHY User Guide (PDF).