PM0214 datasheet(48/245 Pages) STMICROELECTRONICS

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The Cortex-M4 processor

PM0214

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DocID022708 Rev 4

Wakeup from WFE

The processor wakes up if:

•

it detects an exception with sufficient priority to cause exception entry

•

it detects an external event signal, see Section 2.5.3: External event input / extended

interrupt and event input

•

in a multiprocessor system, another processor in the system executes an SEV

instruction.

In addition, if the SEVONPEND bit in the SCR is set to 1, any new pending interrupt triggers

an event and wakes up the processor, even if the interrupt is disabled or has insufficient

priority to cause exception entry. For more information about the SCR see System control

2.5.3

External event input / extended interrupt and event input

The processor provides an external event input signal.

For the STM32F4xxx series, this signal can be generated by the up to 16 external input

lines, by the PVD, RTC alarm or by the USB wakeup event, configured through the external

interrupt/event controller (EXTI).

For the STM32F3xxx series, this signal can be generated by the extended interrupt/event

controller (EXTI), which manages up to 29 external and internal asynchronous interrupts

and events.

This signal can wakeup the processor from WFE, or set the internal WFE event register to

one to indicate that the processor must not enter sleep mode on a later WFE instruction, see

Wait for event on page 47. Fore more details please refer to the STM32 reference manual,

section 4.3 Low power modes.

2.5.4

Power management programming hints

ISO/IEC C cannot directly generate the WFI and WFE instructions. The CMSIS provides the

following functions for these instructions:

void __WFE(void) // Wait for Event

void __WFI(void) // Wait for Interrupt

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