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The TPIU can output trace data in a Serial Wire Output (SWO) format:
When one of the two SWO modes is selected, you can enable the TPIU to bypass the formatter for trace output. If the formatter is bypassed, only one trace source passes through. When the formatter is bypassed, only data on the ATB interface 1 is passed through and ATB interface 2 data is discarded.
When operating in bypass mode, Arm® recommends that in a configuration that supports and ETM and ITM, the ITM data is passed through by connecting the ITM to the ATB Slave Port 1.