E-Tile frequency constraints

Hi,

I've a question regarding the E-Tile transceiver and their constraints.

I would like to implement different data rates which I have already tested successfully using the reconfiguration interface.

Now I'd like to ask if it's necessary to create a constraint for the minimum and maximum frequency.

My intention would be to instantiate the E-Tiles with a lower data rate and create constraints for the minimum and maximum frequency used for RX/TX_out_clock.

I already tried it with the create_clock constraint to create it with their periods but obviously the values are truncated.

Can I specify ps or fs instead of ns for the clock period?

Another possibility would be:

Should I specify the highest data rate and the lower ones will be possible without timing violations, too?

Which 'strategy' would be the better one to avoid any issues with the E-Tiles during operation?

Best regards,

Michael