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AR# 39945

ISE Constraints - Propagation of TNM and TNM_NET grouping constraints


I have applied the following grouping constraint but my PADs are not included.

NET "Test[*]" TNM_NET="Test_GRP";

Why are the PADs not been included in this group?


The Timing Name Net (TNM_NET) constraint is essentially equivalent to Timing Name (TNM) on a net except for input pad nets.

TNM does not propagate through IBUF or BUFG components.

The Timing Name is placed on the input pad.
The TNM_NET constraint does propagate through IBUF and global clock buffers.
Xilinx recommends:
  • Use TNM to group instances and macros (hierarchical blocks).
  • To group input pads, use a TNM on the net, driven by a pad.
  • Use TNM_NET to group several (many) logic elements driven by a net, such as clocks, clock enables, chip enables, read/writes, and resets.

You should use the following to group PADs:

NET "Test[*]" TNM = Test_GRP";

For more information on TNM and TNM_NET, please see (UG625) Constraints Guide.
AR# 39945
Date Created 01/05/2011
Last Updated 01/21/2015
Status Active
Type General Article
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