It seems I have a strange problem with my timing constraints, I have recently generated a tsi report using the xilinx trace tool(using ISE
5.2),
trce -tsi file.tsi file.ncd file.pcf -v 5 -u 5 -skew -o file.v.twr
The report states that a considerable number of nets in our design fall under the constraint "Unconstrained path analysis". We have multiple clock domains in our design so I initially assumed that the unconstrained nets would be on the synchronisation buffers (which might not be completely covered by the period constraints we have assigned for all of our clocks), however when I checked the offending nets I found that many reffered to FFS whose input and output connections were all on the same clock domain. I am unsure at this stage how these nets got into the unconstrained section as their inputs and outputs only feed FFS on the same domain. The reason this is a problem is that there is a constraints intersection issue between the unconstrained section and my other constraints. Denis