An ETM is a debug component that enables reconstruction of program execution. ETM is a high-speed, low-power debug tool that only supports instruction trace. Therefore, ETM helps in minimizing area and reducing gate count.
The main features of an ETM are:
Trace generation outputs information that helps understand the operation of the processor. The trace protocol provides a real-time trace capability for processor cores that are deeply embedded in much larger ASIC designs.
You can control tracing by specifying the exact set of triggering and filtering resources required for a particular application. Resources include address comparators, data value comparators, counters, and sequencers.
ETM compresses the trace information and writes it directly to an on-chip ETB. An external Trace Port Analyzer (TPA) captures the trace information. The trace is read out at low speed using the JTAG interface when the trace capture is complete.
When the trace has been captured, the profiling and analysis tool extracts the information from ETB and decompresses it to provide a full disassembly, with symbols, of the code that was executed.