XDC Constraints Order - 2022.1 English

Vivado Design Suite User Guide: Using Constraints (UG903)

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2022.1 English

XDC constraints are commands interpreted sequentially. For equivalent constraints, the last constraint takes precedence.

Constraints Order Example:

> create_clock -name clk1 -period 10 [get_ports clk_in1]
> create_clock -name clk2 -period 11 [get_ports clk_in1]

In this example, the second clock definition overrides the first clock definition because:

  • They are both attached to the same input port.
  • The create_clock -add option was not used.