Making and Splitting Differential Pairs - 2023.2 English

Vivado Design Suite User Guide: I/O and Clock Planning (UG899)

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2023.2 English
To define a differential pin pair in an I/O planning project:
  1. In the I/O Ports window, select any two I/O ports, right-click, and select Make Diff Pair.
    Important: The Make Diff Pair option is not available in RTL projects. In RTL projects, differential ports must be defined in the source code using appropriate I/O buffer instantiations.

    In the Make I/O Diff Pair dialog box (see the following figure), the two I/O Ports display with Positive End and Negative End assignments made by the tool.

  2. To reverse the Positive End and Negative End signals, click Swap, and click OK.
    Tip: Right-click, and select Split Diff Pair to separate a diff pair into two ports.
    Important: When you apply certain constraints to one side of a differential pin pair in an AMD UltraScale™ architecture, the opposite constraint is automatically applied to the other side. For example, if you apply a PULLDOWN constraint to the P side, a PULLUP constraint is applied to the N side. If you make changes to the constraints, the most recent settings overwrite previous settings.