STM32L471XX Datasheet, PDF (25/218 Pages) STMicroelectronics – Batch acquisition mode

STM32L471xx
Functional overview
By default, the microcontroller is in Run mode after a system or a power Reset. It is up to the
user to select one of the low-power modes described below:
• Sleep mode
In Sleep mode, only the CPU is stopped. All peripherals continue to operate and can
wake up the CPU when an interrupt/event occurs.
• Low-power run mode
This mode is achieved with VCORE supplied by the low-power regulator to minimize
the regulator's operating current. The code can be executed from SRAM or from Flash,
and the CPU frequency is limited to 2 MHz. The peripherals with independent clock can
be clocked by HSI16.
• Low-power sleep mode
This mode is entered from the low-power run mode. Only the CPU clock is stopped.
When wakeup is triggered by an event or an interrupt, the system reverts to the low-
power run mode.
• Stop 0, Stop 1 and Stop 2 modes
Stop mode achieves the lowest power consumption while retaining the content of
SRAM and registers. All clocks in the VCORE domain are stopped, the PLL, the MSI
RC, the HSI16 RC and the HSE crystal oscillators are disabled. The LSE or LSI is still
running.
The RTC can remain active (Stop mode with RTC, Stop mode without RTC).
Some peripherals with wakeup capability can enable the HSI16 RC during Stop mode
to detect their wakeup condition.
Three Stop modes are available: Stop 0, Stop 1 and Stop 2 modes. In Stop 2 mode,
most of the VCORE domain is put in a lower leakage mode.
Stop 1 offers the largest number of active peripherals and wakeup sources, a smaller
wakeup time but a higher consumption than Stop 2. In Stop 0 mode, the main regulator
remains ON, allowing a very fast wakeup time but with much higher consumption.
The system clock when exiting from Stop 0, Stop1 or Stop2 modes can be either MSI
up to 48 MHz or HSI16, depending on software configuration.
• Standby mode
The Standby mode is used to achieve the lowest power consumption with BOR. The
internal regulator is switched off so that the VCORE domain is powered off. The PLL,
the MSI RC, the HSI16 RC and the HSE crystal oscillators are also switched off.
The RTC can remain active (Standby mode with RTC, Standby mode without RTC).
The brown-out reset (BOR) always remains active in Standby mode.
The state of each I/O during standby mode can be selected by software: I/O with
internal pull-up, internal pull-down or floating.
After entering Standby mode, SRAM1 and register contents are lost except for registers
in the Backup domain and Standby circuitry. Optionally, SRAM2 can be retained in
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