ST STM32L0x3 User Manual

RM0367 Rev 7 159/1043
RM0367 Power control (PWR)
172
Note: To be able to read the RTC calendar register when the APB1 clock frequency is less than
seven times the RTC clock frequency (7*RTCLCK), the software must read the calendar
time and date registers twice.
If the second read of the RTC_TR gives the same result as the first read, this ensures that
the data is correct. Otherwise a third read access must be done.
Exiting Low-power sleep mode
The Low-power sleep mode is exited according to Section 6.3.6: Exiting low-power mode.
When exiting Low-power sleep mode by issuing an interrupt or a wakeup event, the
regulator is configured in Main regulator mode, the Flash memory is switched on (if
necessary), and the system clock can be increased.
When the voltage regulator operates in low-power mode, an additional startup delay is
incurred when waking up from Low-power sleep mode.
Refer to Table 35: Sleep-now (Low-power sleep) and Table 36: Sleep-on-exit (Low-power
sleep) for more details on how to exit Sleep low-power mode.
Table 35. Sleep-now (Low-power sleep)
Sleep-now mode Description
Mode entry
Voltage regulator in low-power mode and the Flash memory switched off
WFI (Wait for Interrupt) or WFE (wait for event) while:
– SLEEPDEEP = 0 and
– No interrupt (for WFI) or event (for WFE) is pending
Refer to the Cortex
®
-M0+ System Control register (see PM0223 programming
manual).
On return from ISR while:
– SLEEPDEEP = 0 and
– SLEEPONEXIT = 1 and
– No interrupt is pending
Refer to the Cortex
®
-M0+ System Control register (see PM0223 programming
manual).
Mode exit
Voltage regulator in Main regulator mode and the Flash memory switched on
If WFI or Return from ISR was used for entry:
Interrupt: Refer to Table 55: List of vectors
If WFE was used for entry and SEVONPEND = 0
Wakeup event: Refer to Section 13.3.2: Wakeup event management
If WFE was used for entry and SVONPEND = 1
Interrupt event when disabled in NVIC (refer to Table 55: List of vectors) or
wakeup event (refer to Section 13.3.2: Wakeup event management)
Wakeup latency Regulator wakeup time from low-power mode

ST STM32L0x3 Specifications

General

Brand	ST
Model	STM32L0x3
Category	Microcontrollers
Language	English