Altera's Quartus has 3 ways to assign pins to the FPGA device:
1. Assignment Editor.
2. Pin Planner.
3. Direct text input into *.QSF.
My question:
Are these tools synchronized with each other?
For example: if I do initial assignments using the Pin Planner and then make changes in the *.QSF file - will the changes in the QSF propagate back to the Pin Planner settings?
As long as you save the changes to the QSF, I 'm pretty sure they get loaded for each tool (you may have to close and reopen the tool to get the latest changes), but I might be mis-remembering as it's been 5-6 years since I've used Quartus.
Any changes you make via assignment editor and pin planner are written to the QSF file (stands for quartus settings file I think). Quartus uses the QSF file to set up the assignment editor and pin planner (and all the other stuff in its gui). Ensure you havent got the project open when you hand edit the .qsf though
You can also assign pins via attributes in the HDL.