Example - Example - 2026.1 English - UG906

Vivado Design Suite User Guide: Design Analysis and Closure Techniques (UG906)
Document ID
UG906
Release Date
2026-06-23
Version
2026.1 English

In the following figure, the primary clock definition using the create_clock constraint is placed on the output pin of the input buffer control (IBUFCTRL) instance. If the clock clk_pin_p is used to time an input or output port path, the slack is inaccurate because part of the clock tree insertion delay is missing.

Place the primary clock definition for the differential input buffer 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