What are the "Automatic lock-to-reference functions"?
The plurality of "functions" is a bit misleading, as there is really only one lock-to-reference function. If there are no transitions on the RXP and RXN inputs, RXRECCLK will lock to REFCLK. Since the CDR's PLL can withstand 75 non-transitioning bits, this will not happen until that number has been exceeded.