How can I lock the instances inside the Pblock (from one run) so that it will not change in the next run?
You can export the locations of all the instances inside the pblock to a UCF file and use it in the design.
Please follow the steps below.
Open the synthesized design. Create a pblock and assign instances to it.
Save the design and run implementation.
Open the implemented design.
Go to File --> Export --> Export Pblocks as shown below:
- This directs you to a dialog box as shown below.
Here check the option Export all placement and select the pblock to be exported.
Enter a location to save the exported files to and click on OK.
- Browse to the specified location.
You will find a folder with the name pblock_name_CV.
This constrains the UCF file with the desired constraints.