Inserting SignalTap without re-routing design

Your top-level is in a partition automatically, so:

1) Make a copy of the design that has the problem, including /db and /incremental_db. (Basically copy the directory with the .qpf/.qsf in it and all sub-directories)

2) Assignments -> Design Partition Window to open it

3) Set the Top partition(and any you might have created) to Post-Fit. If you want, you can right click on them and go to Partition Properties and click the option to Ignore Changes in Source Files, in which case they will always be Post-Fit even if you change your source, but this shouldn't be necessary.

4) Add SignalTap, and be sure to only tap SignalTap: Post Fit nodes. The main thing to look for is registers, as they should be kept and have a name that makes sense.

5) Compile. SignalTap is its own partition, so it will get synthesized independently and then placed-and-routed around your post-fit partition/s.

6) Modify SignalTap and repeat until you find the problem.

7) Be sure to set the partition back to Source or Post-Synthesis and uncheck Ignore Changes in Source if you had checked that.