wfi

Wait For Interrupt

WFI

Puts the processor into a low-power state until an interrupt occurs.

Details

Puts the processor core into a low-power wait state until an interrupt occurs. Execution resumes transparently at the next instruction after the interrupt is serviced. No condition flags are affected. Execution state: AArch64-only.

Pseudocode Operation

# Enter low-power state
while (no_interrupt_pending) do
  wait_for_interrupt
PC ← PC + 4

Example

WFI

Encoding

Binary Layout

11010101000000110010

0000

011

11111

Format System Alias

Opcode 0xD503207F

Extension Base

Operands

Reference (Arm A64 ISA)

Instruction Forms

Encoding	Instruction		ISA		Bit pattern
0xD503207F	WFI		A64		11010101000000110010 \| 0000 \| 011 \| 11111

Description

Wait For Interrupt is a hint instruction that indicates that the PE can enter a low-power state and remain there until a wakeup event occurs. For more information, see Wait For Interrupt. As described in Wait For Interrupt, the execution of a WFI instruction that would otherwise cause entry to a low-power state can be trapped to a higher Exception level.

Operation

integer localtimeout = 1 << 64;    // No local timeout event is generated
Hint_WFI(localtimeout, WFxType_WFI);