ST STM32L1 Series Application Note page 13

AN3413
In Standby mode, the device is in its deepest energy saving state. The device enters the
Cortex-M3 deepsleep mode and the voltage regulator is disabled. All oscillators are
switched off. SRAM and register contents are lost with the exception of the RTC registers,
RTC backup registers and Standby circuitry. The device is woken up from this mode by an
external wakeup event generated by the U3 counter invoking a system reset.
Figure 5. Low power mode flowchart
START
LCD disable
LCD clock OFF
RTC clock source None *
RTC clock OFF *
Regulator in Ultra low power mode **)
GPIO Low power config
Disable external counter U3
Disable fast wakeup
Configure LP clock
Configure interrupt/event
Switch OFF flash memory ***)
Switch OFF regulator
WFE set to external event from PA0
Enable external counter U3
Wait For Event or
Wait For Interrupt
Event or
Interrupt
occurred?
YES
Clear interrupt / event
Switch ON regulator
Reconfigure clock
END
DocID018933 Rev 2
NO
*) except Stop with RTC
**) except Sleep mode
***) only for LP RUN, Sleep and LP Sleep
Software description
MS19816V1
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