The trace-port interface unit (TPIU) outputs packetized trace data to an off-chip analyzer. TPIU adds another layer of framing (packetization). The framing format is designed to make it easy for an analysis tool to re-synchronize to the frame boundary.
The TPIU acts as a bridge between the on-chip trace data with separate IDs to a data stream encapsulating IDs where required that is then captured by a trace port analyzer (TPA). The internal formatter inserts source ID signals into the data packet stream so that trace data can be re-associated with its trace source. It contains an asynchronous FIFO that enables trace data to be driven out at a speed that is not dependent on the on-chip bus clock. The internal trace-out block serializes formatted data before it goes off-chip. The TPIU includes a pattern generator unit that provides a simple set of defined bit sequences or patterns that can be output over the trace port and be detected by the TPA or other associated trace capture device (TCD). The TCD can use these patterns to indicate if it is possible to increase or decrease the trace port clock speed.