Xilinx Property TNM
Use TNM to tag flip-flops with a timing-group name to be used in a Timespec.
XILINX PROPERTY 'TNM=group_name signal_name...';
Where signal_name is the name of a registered node or output pin signal in your design.
Note: If you assign the TNM property to a registered output signal, the fitter will apply it to the flip-flop driving the signal, not the output pad itself.
To assign group names to input and output pads in your top-level ABEL design, use the TNM or TIMEGRP property in the UCF file. For ABEL modules in a schematic design, you can declare group names for your input and output pads in your schematic.