Routing signals in priority

[Altera_Forum]

Hi, 

   do you know if it's possible to force the router tool to route specified signals first.   Thank you Arnaud

[Altera_Forum]

First, the router will give timing critical signals the highest priority, so in essence they are routed first. So your timing constraints already dictate this. (It's not a straightforward "route this first" assignmnet, but usually you want this for timing, and the router is already doing it for timing.) If it's not for timing, what's the benefit of having something routed first?  

You can go to assignments -> Settings -> Back-annotate and do it to the routing level. This will create an .rcf which has all the routes. You can use this, as it's somewhat readable, if you want to preserve specific routes. Just keep what you want and rip the rest out.

[Altera_Forum]

these signals are quite critical. I assign a MAX_DELAY constaints of 1ns. The router can't achieve it.  

i'm quite sure that it can achieve it, because it achieve constraints in a previous routing (design was closed). that's why I want to force the routing of these signals first.   I create the .rcf file. I found signals, I remove others. And do I just to run a compilation? And tools keeps the selected signals? So I have to take the rcf from a design which was correctly routed?

[Altera_Forum]

I think you just add it to the project. Note that the .rcf does not dictate placement, i.e. you need to lock down all the logic in the path, and then the .rcf can route between the nodes after placement. If using TimeQuest, you can do report_timing with the -show_routing option to see the different routes between the one that makes timing and the one that does not. (Sounds like you're using the Classic though...)