Set Event, Wait For Event, Wait for Interrupt, and Yield.
These are hint instructions. It is optional whether they are
implemented or not. If any one of them is not implemented, it executes
NOP. The assembler produces a diagnostic message
if the instruction executes as a
NOP on the target.
NOP instructions in ARMv6T2.
If the Event Register is not set,
execution until one of the following events occurs:
an IRQ interrupt, unless masked by the CPSR I-bit
an FIQ interrupt, unless masked by the CPSR F-bit
an Imprecise Data abort, unless masked by the CPSR A-bit
a Debug Entry request, if Debug is enabled
an Event signaled by another processor using the
If the Event Register is set,
WFE clears it and
WFE is implemented,
also be implemented.