Back-Annotate Assignments Dialog Box

You open this dialog box by clicking on the Assignments > Back-Annotate Assignments

After compilation, you can back-annotate (copy) the Compiler's resource assignments to preserve that same implementation in subsequent compilations. Back-annotation can simplify timing closure by allowing you to lock down placement of your optimized results.

You can specify whether to to preserve Pin assignments, RAM assignments, DSP assignments, Clock assignments, and Clock Spine assignments in the back-annotation.

Locking down placement of large blocks related to Clocks, RAMs, and DSPs can produce higher fMAX with less noise. Large blocks like RAMs and DSPs have heavier connectivity than regular LABs, complicating movement during placement. When a seed produces good results from suitable RAM and DSP placement, you can capture that placement with back-annotation. Subsequent compiles can then benefit from the high quality RAM and DSP placement from the good seed

Important: Important: The Logic Cell Insertion - Logic Duplication and Auto Register Duplication logic options are not compatible with routing back-annotation. If you want to perform routing back-annotation, turn off the Logic Cell Insertion - Logic Duplication and Auto Register Duplication logic options, run the Fitter, and then back-annotate assignments.