Table 27. Standby Mode - STMicroelectronics RM0365 Reference Manual

Power control (PWR)
Section 26.3: IWDG functional description
(IWDG).
•
real-time clock (RTC): this is configured by the RTCEN bit in the RTC domain control
register (RCC_BDCR)
• Internal RC oscillator (LSI RC): this is configured by the LSION bit in the Control/status
register (RCC_CSR).
•
External 32.768 kHz oscillator (LSE OSC): this is configured by the LSEON bit in the
RTC domain control register (RCC_BDCR)
Exiting Standby mode
The microcontroller exits the Standby mode when an external reset (NRST pin), an IWDG
reset, a rising edge on the WKUP pin or the rising edge of an RTC alarm occurs (see
Figure 283: RTC block
for Power control/status register
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
control/status register (PWR_CSR)
Refer to
Standby mode
Mode entry
Mode exit
Wakeup latency
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 ARM
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.
107/1080
diagram). All registers are reset after wakeup from Standby except
Table 27 for more details on how to exit Standby mode.
WFI (Wait for Interrupt) or WFE (Wait for Event) while:
– Set SLEEPDEEP in ARM
– Set PDDS bit in Power Control register (PWR_CR)
– Clear WUF bit in Power Control/Status register (PWR_CSR)
WKUP pin rising edge, RTC alarm event's rising edge, external Reset in
NRST pin, IWDG Reset.
Reset phase
in Section 26: Independent watchdog
(PWR_CSR).
indicates that the MCU was in Standby mode.

Table 27. Standby mode

®
Cortex
DocID025202 Rev 7
Description
®
-M4 System Control register
RM0365
Power
® ®
Cortex -M4