Cyclone V Device Handbook: Volume 2: Transceivers

ID 683586
Date 10/24/2018
Document Table of Contents Lock-to-Reference Mode

In LTR mode, the phase frequency detector (PFD) in the CDR tracks the receiver input reference clock. The PFD controls the charge pump that tunes the VCO in the CDR. Depending on the data rate and the selected input reference clock frequency, the Quartus II software automatically selects the appropriate /M and /L divider values so the CDR output clock frequency is half the data rate. The rx_is_lockedtoref status signal is asserted to indicate that the CDR has locked to the phase and frequency of the receiver input reference clock.

The phase detector is inactive in LTR mode and rx_is_lockedtodata is ignored.