RM0444 Rev 5 135/1390
RM0444 Power control (PWR)
159
4.3.6 Stop 0 mode
The Stop 0 mode is based on the Cortex
®
-M0+ deepsleep mode combined with the
peripheral clock gating. The voltage regulator is configured in main regulator mode. In Stop
0 mode, all clocks in the V
CORE
domain are stopped; the PLL, the HSI16 and the HSE
oscillators are disabled. Some peripherals with the wakeup capability (I2C1, USART1,
USART2, and LPUART1) can switch on the HSI16 to receive a frame, and switch off the
HSI16 after receiving the frame if it is not a wakeup frame. In this case, the HSI16 clock is
propagated only to the peripheral requesting it.
SRAM and register contents are preserved.
The BOR is available in Stop 0 mode.
The BOR and PDR can be activated to sample periodically the supply voltage. This option
enabled by setting the ENB_ULP bit of the PWR_CR3 register allows decreasing the
current consumption in this mode, but any drop of the voltage below the operating
conditions between two active periods of the supply detector results in a non-generation of
PDR reset.
I/O states in Stop 0 mode
In the Stop 0 mode, all I/O pins keep the same state as in the Run mode.
Table 29. Low-power sleep mode summary
Characteristic Description
Mode entry
Low-power sleep mode is entered from the Low-power run mode.
WFI (Wait for Interrupt) or WFE (Wait for Event) while:
– SLEEPDEEP = 0
– No interrupt (for WFI) or event (for WFE) is pending
Refer to the Cortex
®
-M0+ System Control register.
Low-power sleep mode is entered from the Low-power run mode.
On return from ISR while:
– SLEEPDEEP = 0 and
– SLEEPONEXIT = 1
– No interrupt is pending
Refer to the Cortex
®
-M0+ System Control register.
Mode exit
If WFI or Return from ISR was used for entry
Interrupt: refer to Table 58: Vector table
If WFE was used for entry and SEVONPEND = 0:
Wakeup event: refer to Section 13.3.2: EXTI direct event input wakeup
If WFE was used for entry and SEVONPEND = 1:
Interrupt even when disabled in NVIC: refer to Table 58: Vector table
Wakeup event: refer to Section 13.3.2: EXTI direct event input wakeup
After exiting Low-power sleep mode, the MCU is in Low-power run mode.
Wakeup latency None
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