The functional interfaces of the TPIU are:
ATB slave interface, for receiving trace data.
APB slave interface, for accessing the TPIU registers.
Trace out port, for connecting to the external trace port pins.
trigin and flushin event interfaces. These implement synchronizers so that they can be connected to a CTI in a different clock domain.
The TPIU also supports the extctlin[7:0] and extctlout[7:0] signals. These are designed to enable debug tools to multiplex the pins used by the trace out port with other functions.