The Trace Port Interface Unit (TPIU) is an Arm Coresight component which routes the incoming trace data from one or more sources to an output pin interface. The incoming data ports can be ITM, ETM or PTM. The supported output pins are SWO and trace pins. The input data is then framed and formatted and sent out to the corresponding pins.
Usually the TPIU comes with a built in clock divider for trac pins of 1/2.
There is also a smaller variant of the TPIU called the TPIU-Lite.