4.9 Debugging: Xtrace and Advance Dataflow The Xtrace command in Riviera-PRO creates a report with information about unknown values in a simulated model. These values can be X, U, or any other value. Xtrace has the ability to cross-probe with Dataflow to provide a visualization of the simulated model in order to locate the source of the unknown values. This video will demonstrate how to utilize Xtrace with Dataflow to trace and debug signals of unknown values.