New Contributor
Regular ContributorHi,
As I understand it, in your latest observation, you found that the rx_is_lockedtodata signal = low. I believe you are seeing it toggling periodically. If this is the case, it indicates that the CDR is unable to achieve lock to the data.
You can also check if the rx_is_lockedtoref = high to check if the CDR has successfully locked to the refclk. Note that when rx_is_lockedtodata = 1, the state of the rx_is_lockedtoref can be ignored.
Common causes for the CDR to unable to lock to data are signal integry issue, incorrect data rate, local refclk signal integrity issue, incoming data's ppm exceed CDR threshold and offset cancellation issue. You can try to debug into these to see if can spot any anomaly.
Please let me know if there is any concern. Thank you.
New ContributorChee Pin
One last question.
What IO_STANDARD should the SLVS-EC inputs use? I have specified LVDS in my .qsf but is there something more appropriate in terms of input voltage swing?
