RM0444 Rev 5 141/1390
RM0444 Power control (PWR)
159
4.3.9 Shutdown mode
The Shutdown mode allows to achieve the lowest power consumption. It is based on the
deepsleep mode, with the voltage regulator disabled. The V
CORE
domain is consequently
powered off. The PLL, the HSI16, the LSI and the HSE oscillators are also switched off.
SRAM and register contents are lost except for registers in the RTC domain. The POR/PDR
and BOR are not available in Shutdown mode. No power voltage monitoring is possible in
this mode. As a result, the switch of the RTC domain to V
BAT
supply when V
DD
supply is lost
is not supported.
I/O states in Shutdown mode
In the Shutdown mode, the I/Os can be configured either with a pull-up (refer to
PWR_PUCRx registers (x=A, B, C, D, F), or with a pull-down (refer to PWR_PDCRx
registers (x=A, B, C, D, F)), or can be kept in analog state. However this configuration is lost
when exiting Shutdown mode due to the power-on reset.
The RTC outputs on PC13 are functional in Shutdown mode. PC14 and PC15 used for LSE
are also functional. Five wakeup pins (WKUPx, x=1,2,4,5,6) and the two tampers are
available.
Entering Shutdown mode
The MCU enters Shutdown mode according to section Entering low-power modes, when the
SLEEPDEEP bit in the Cortex
®
-M0+ System Control register is set.
Refer to Table 33: Shutdown mode summary for details on how to enter Shutdown mode.
In Shutdown mode, the following features can be selected by programming individual
control bits:
• Real-time clock (RTC) and tamper (TAMP): this is configured by the RTCEN bit in the
RTC domain control register (RCC_BDCR).
• External 32.768 kHz oscillator (LSE): this is configured by the LSEON bit in the RTC
domain control register (RCC_BDCR).
Caution: The RTC domain content is lost when V
DD
is powered down under Shutdown mode.
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