Example - 2025.1 English - UG906

Vivado Design Suite User Guide: Design Analysis and Closure Techniques (UG906)
Document ID
UG906
Release Date
2025-05-29
Version
2025.1 English

In the following figure, the primary clock definition, the create_clock constraint, was placed on the output pin of the IBUFCTRL instance. If the clock clk_pin_p is used to time an input or output port path, the slack will be inaccurate because part of the clock tree insertion delay will be missing. The primary clock definition for the differential input buffer should be placed on the top-level port clk_pin_p.

Figure 1. Invalid Primary Clock on Internal Pin
Page-1 Sheet.1 Process Create the primary clock on the startpoint of the clock tree Create the primary clock on the startpoint of the clock tree Sheet.3 Process.5 Primary clock defined on an internal pin Primary clock defined on an internal pin Sheet.5 Sheet.8 X15523-111715 X15523-111715