Power control (PWR) RM0008
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Exiting Standby mode
The microcontroller exits Standby mode when an external Reset (NRST pin), IWDG Reset,
a rising edge on WKUP pin or an RTC alarm occurs. All registers are reset after wakeup
from Standby except for Power control/status register (PWR_CSR).
After waking up from Standby mode, program execution restarts in the same way as after a
Reset (boot pins sampling, vector reset is fetched, etc.). The SBF status flag in the Power
control/status register (PWR_CSR) indicates that the MCU was in Standby mode.
Refer to Ta bl e 1 1 for more details on how to exit Standby mode.
I/O states in Standby mode
In Standby mode, all I/O pins are high impedance except:
● Reset pad (still available)
● TAMPER pin if configured for tamper or calibration out
● WKUP pin, if enabled
Debug mode
By default, the debug connection is lost if the application puts the MCU in Stop or Standby
mode while the debug features are used. This is due to the fact that the Cortex™-M3 core is
no longer clocked.
However, by setting some configuration bits in the DBGMCU_CR register, the software can
be debugged even when using the low-power modes extensively. For more details, refer to
Section 26.15.1: Debug support for low-power modes.
Table 11. Standby mode
Standby mode Description
Mode entry
WFI (Wait for Interrupt) or WFE (Wait for Event) while:
– Set SLEEPDEEP in Cortex™-M3 System Control register
– Set PDDS bit in Power Control register (PWR_CR)
– Clear WUF bit in Power Control/Status register (PWR_CSR)
Mode exit
WKUP pin rising edge, RTC alarm, external Reset in NRST pin, IWDG
Reset.
Wakeup latency Regulator start up. Reset phase
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