06-07-2019 05:21 AM
I don't know if this has been reported yet or not, but I just ran the Timing Constraints Wizard with Vivado 2017.2 and it blew away about a third of my pin constraints.
06-07-2019 05:43 AM
Yes, the Constraints Wizard has the “blown away” problem – even in v2018.3 Vivado.
The Constraints Wizard will successfully help you add new constraints to the project XDC file, but also tends to make a mess of your XDC file by: 1) erasing in-line comments, 2) replacing/erasing expressions with Tcl variables and leaving you with numbers (now meaningless since variables used to create the numbers are erased).
Thus, if you are planning to use the Constraints Wizard then you should first backup your XDC file. Then, you can manually copy the good things done by the Wizard from your “blown away” XDC file to the backup XDC file.
06-07-2019 07:20 AM
You can also add a new constraint file to the constraint set and mark it the target. Once you are done with the constraint editor, move the constraints to the clean file.