PM0223 datasheet(35/110 Pages) STMICROELECTRONICS

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PM0223

The STM32L0 Cortex-M0+ Processor

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 2.5.3: The external event input on page 35.

•

In a multiprocessor system, another processor in the system executes a 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 pri-

ority to cause exception entry. For more information about the SCR, see 4.3.6: System Con-

trol Register on page 92.

2.5.3

The external event input

The processor provides an external event input signal. This signal can be generated by

peripherals. Tie this signal LOW if it is not used.

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 34.

2.5.4

Power management programming hints

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

the following intrinsic functions for these instructions:

void __WFE(void) // Wait for Event

void __WFI(void) // Wait for Interrupt

void __SEV(void) // Send Event

PM0223 Datasheet(PDF) 35 Page - STMicroelectronics