how can I get best constraint result.

[ackqin]

I am doing a project, the running frequency is not satisfied. so I tried to add some timing constraints to it, but I don't know whether I should add it on synplify or ise using UCF. also I have a lot puzzle about timing constraint, how can I recognize the critical path in ise, is there some document about this issue? Can anybody give the address.

Thanks a lot.

ackqin

 

[xysafety]

After synthesis of ISE, you can see the critical path from the report.