When I run Modular Design with the -p or -r option in PAR, the following error is reported:
"ERROR:DesignRules:10 - Netcheck: The signal "xxx" is completely unrouted."
Xilinx recommends that you do not use the -p and the -r options with Modular Design.
Using the -p and -r options causes unexpected results with PAR. The -r option specifies that only the placer be run, and the -p option specifies that only the router be run. The unexpected results occur because guide is run in both cases. Without the -p and the -r options, the flow is as follows:
Guide -> Place -> Route
However, if PAR is run with -r and then run with -p, the flow is as follows:
Guide -> Place -> Guide (again) -> Route
This additional guide phase between place and route causes the problem.