8.2.3 Wakeup event management Cortex-M3 is able to handle external events or internal events in order to wake up the core (WFE). By configuring the external lines any I/O port, RTC Alarm and USB Wakeup Events can be used to wake up the CPU (exit from WFE). To use an external line as a wakeup event, refer to Section 8.2.4: Functional description.