Sleep mode (WFI instruction) in ARM Architecture - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the WFI instruction do in ARM architecture?

The WFI (Wait For Interrupt) instruction puts the processor into a low-power sleep mode until an interrupt occurs.

beginner

How does the processor wake up from sleep mode after executing WFI?

The processor wakes up when it receives an enabled interrupt or a reset signal, resuming normal operation.

intermediate

Why is using WFI beneficial in embedded systems?

Using WFI reduces power consumption by stopping the processor until work is needed, which is important for battery-powered devices.

intermediate

Can the WFI instruction be interrupted by any event?

No, only enabled interrupts or reset signals can wake the processor from WFI sleep mode.

beginner

What happens if no interrupt occurs after executing WFI?

The processor remains in sleep mode, consuming less power, until an enabled interrupt or reset wakes it.

What is the primary purpose of the WFI instruction?

A To put the processor into low-power sleep mode until an interrupt occurs

B To reset the processor immediately

C To execute a system call

D To start a timer

WFI stands for Wait For Interrupt and it puts the processor to sleep until an interrupt wakes it.

Which event can wake the processor from WFI sleep mode?

A Only enabled interrupts or reset signals

B Any signal on the data bus

C A software loop

D Power off

Only enabled interrupts or reset signals can wake the processor from WFI sleep mode.

What happens if no interrupt occurs after WFI is executed?

A Processor restarts

B Processor shuts down

C Processor continues normal operation

D Processor stays in sleep mode

Without an interrupt, the processor remains in sleep mode to save power.

Why is WFI useful in battery-powered devices?

A It increases processing speed

B It improves graphics performance

C It reduces power consumption by sleeping when idle

D It disables interrupts

WFI reduces power use by putting the processor to sleep when no work is needed.

Which of the following best describes the WFI instruction?

A An instruction to wait for a timer event

B An instruction to wait for an interrupt

C An instruction to reset the CPU

D An instruction to start a peripheral

WFI means Wait For Interrupt, so it waits for an interrupt to wake the CPU.

Explain how the WFI instruction helps save power in ARM processors.

Think about what happens when the processor is idle and how WFI changes that.

Describe the conditions under which the processor wakes up from sleep mode after executing WFI.

Focus on what events can interrupt the sleep state.