Exceptions Priority with -reset_path Example - Exceptions Priority with -reset_path Example - 2026.1 English - UG903

Vivado Design Suite User Guide: Using Constraints (UG903)
Document ID
UG903
Release Date
2026-07-01
Version
2026.1 English
set_false_path -from [get_clocks clkA] -to [get_clocks clkB]
set_max_delay 1 -from [get_clocks clkA] -to [get_clocks clkB] -reset_path

The paths between clocks clkA and clkB are covered by the Max Delay constraint with a path requirement of 1 ns. The Max Delay uses the same values for -from and -to and includes the -reset_path option, which overrides the False Path constraint. 

set_false_path -from [get_clocks clkA] -to [get_clocks clkB]
set_max_delay 1 -from [get_pins reg0/CLK] -to [get_pins reg1/D] -reset_path

The paths between reg0/CLK and reg1/D remain covered by the False Path because that constraint has higher precedence than the Max Delay. The Max Delay does not override the False Path, even with -reset_path, because it does not use identical values for -from and -to.

Recommended: Avoid applying multiple timing exceptions to the same paths. This prevents analysis results from depending on priority rules and makes it easier to verify the effect of your constraints.

Use the report_exceptions command to validate your timing exceptions. This command shows which constraints are overridden or ignored. For more details, refer to the Vivado Design Suite User Guide: Design Analysis and Closure Techniques (UG906).

If you pass a string to a constraint instead of an object, the Tcl interpreter uses the following order to resolve the match:

  1. port
  2. pin
  3. cell
  4. net

The search is not exhaustive. When objects of a type match the string pattern, the interpreter returns them, even if later objects of another type also match the same pattern.