Download Energy Optimization - AN0027 - Application Note

...the world's most energy friendly microcontrollers
Figure 4.3. energyAware Profiler
4.2.1 Serial Wire Output
In addition to the regular Serial Wire Debug pins for programming and debugging, the EFM32 also
include an optional instrumentation trace feature called Serial Wire Output (SWO). This system allows
the ARM Cortex-M devices to output periodic samples of the Program Counter (PC) or debug statements
from the application code. Once the SWO has been set up to output PC samples, the energyAware
Profiler is able to collect these samples from the kit through the debug interface. By loading the output
file (.out) from the compilation of the program into the Profiler, the tool can link the PC samples to the
compiled C-code for any given point in time. Clicking on the power graph the code window will show the
code that is running at that point in the graph. This is a very useful tool to identify what code is actually
running during periods of higher power consumption. Keep in mind that the SWO sample rate used in
the energyAware Profiler PC sampling is around 2ksamples/s, so it will not give a cycle accurate trace
of the program flow.
2013-11-25 - an0027_Rev1.03
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