On Jul 1, 6:05*am, "Symon" <symon_bre...@hotmail.com> wrote:
> http://www.xilinx.com/itp/xilinx7/bo...gd0140_101.htm...

I've always used the NET keyword, as opposed to PIN, e.g.:

NET top_level_port_name LOC = "A23";

I'm not sure about the assumption that all the timing issues will be
taken care of by the tools, though. Letting the tools choose the
pinout, and then locking them down, might be safer.