
Power control (PWR)
RM0453
250/1454
RM0453 Rev 2
I/O states in Standby mode
In Standby mode, the I/Os can be configured either with a pull-up (refer to PWR_PUCRx
registers (x = A, B, C, H)), or with a pull-down (refer to PWR_PDCRx registers (x = A, B, C,
H)), or can be kept in analog state.
The RTC output on PC13 only is functional in Standby mode. PC14 and PC15 used for LSE
are also functional. Three wakeup pins (WKUPx, x = 1, 2, 3) and the three TAMP tampers
are available.
The sub-GHz radio is functional and PVD can be enabled.
Enter Standby mode
The Standby mode is entered according
, when the SLEEPDEEP bit in the
Cortex system control register is set (see
for details).
In Standby mode, the following features can be selected by programming individual control
bits:
•
Independent watchdog (IWDG): the IWDG is started by writing to its key register or by
hardware option. Once started it cannot be stopped except by a reset. See
Section 30.3: IWDG functional description
.
•
Real-time clock (RTC): this is configured by the RTCEN bit in the Backup domain
control register (RCC_BDCR)
•
Internal RC oscillator (LSI): this is configured by the LSIxON bit in the control/status
register (RCC_CSR).
•
External 32.768 kHz oscillator (LSE): this is configured by the LSEON bit in the Backup
domain control register (RCC_BDCR)
•
Sub-GHz radio activity, as programmed, see
Section 5: Sub-GHz radio (SUBGHZ)
.
•
PVD detection configured in
PWR control register 3 (PWR_CR3)
.
Exit Standby mode
The Standby mode is exited according to
. The SBF status flags (CnSBF) in
the
PWR extended status and status clear register (PWR_EXTSCR)
indicate that the MCU
was in Standby mode. All registers are reset after wakeup from Standby except for
extended status and status clear register (PWR_EXTSCR)
.