Understanding False Paths

You use the set_false_path constraint to tell the timing analyzer not to analyze (that is, to cut) a path. For example, a clock may only toggle some of the time, and you do not want software to try to optimize timing for it.

You can cut paths between entire clock domains or individual points on the timing graph. If you want to completely cut the path between two clock domains, you should instead use the set_clock_groups constraint.