“FROM-TO” Constraints (2)

• GLOBAL “FROM-TO” constraints may apply to all paths of a certain type using keywords or pre-defined groups

  • Example:

TIMESPEC TS03 = FROM PADS TO FFS18 ns;

• Legal keywords (pre-defined groups) are PADS, FFS, LATCHES, and RAMS

• Recommendation for best run-time:

  • Use Period and OFFSET for global constraints
  • Use “FROM-TO” type for blocks or paths within the design

• Exception:

  • OFFSET may only be defined in a UCF file
  • “FROM-TO” constraints may be defined in schematics

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