XDC Constraints Order - 2021.2 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.