If the user decides to use a different reference clock, whether it is an entirely different clock source or the same clock source but with only changes in the actual frequency, additional steps need to be followed when performing the rate change.
If the user decides to use a different reference clock port/source, the current reference clock source must be kept unchanged and stable during the entire rate change sequence. At the same time, the new reference clock source should be set and stable when the rate change procedure starts. The following timing diagram shows the required sequence.
Figure 1. Transceiver Rate Change with Changes in REFCLK Source
Figure 2. Transceiver Rate Change with Changes in REFCLK Frequency without Port Change