Sleep mode (WFI instruction) in ARM Architecture - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to enter sleep mode using the WFI instruction.

ARM Architecture

asm volatile ("[1]" );

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AWFI

BWFE

CNOP

DSVC

Attempts:

3 left

💡 Hint

Common Mistakes

Using WFE instead of WFI

Using NOP which does nothing

Using SVC which triggers a supervisor call

The WFI instruction tells the processor to enter sleep mode and wait for an interrupt.

2fill in blank

medium

Complete the code to enable sleep mode by setting the SLEEPDEEP bit before WFI.

ARM Architecture

SCB->SCR |= [1];
asm volatile ("WFI");

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ASCB_SCR_SLEEPONEXIT_Msk

BSCB_SCR_SEVONPEND_Msk

CSCB_SCR_SLEEPDEEP_Msk

DSCB_SCR_SLEEP_Msk

Attempts:

3 left

💡 Hint

Common Mistakes

Using SLEEPONEXIT instead of SLEEPDEEP

Using SEVONPEND which controls event behavior

Using a non-existent SLEEP mask

The SLEEPDEEP bit in the System Control Register (SCR) must be set to enter deep sleep mode before executing WFI.

3fill in blank

hard

Fix the error in the code to correctly enter sleep mode with WFI.

ARM Architecture

SCB->SCR &= ~[1];
asm volatile ("WFI");

Drag options to blanks, or click blank then click option'

ASCB_SCR_SLEEP_Msk

BSCB_SCR_SLEEPONEXIT_Msk

CSCB_SCR_SEVONPEND_Msk

DSCB_SCR_SLEEPDEEP_Msk

Attempts:

3 left

💡 Hint

Common Mistakes

Using SLEEPONEXIT instead of SLEEPDEEP

Using SEVONPEND which is unrelated

Using a non-existent SLEEP mask

The SLEEPDEEP bit in the System Control Register (SCR) must be cleared to enter normal sleep mode (not deep sleep) before executing WFI.

4fill in blank

hard

Fill both blanks to set the processor to deep sleep mode and then enter sleep.

ARM Architecture

SCB->SCR [1]= [2];
asm volatile ("WFI");

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A|

B&

CSCB_SCR_SLEEPDEEP_Msk

D~SCB_SCR_SLEEPDEEP_Msk

Attempts:

3 left

💡 Hint

Common Mistakes

Using AND (&) instead of OR (|) to set bits

Using the complement (~) mask incorrectly

Clearing bits instead of setting

Use bitwise OR (|) to set the SLEEPDEEP bit before executing WFI to enter deep sleep mode.

5fill in blank

hard

Fill all three blanks to clear the deep sleep bit, set the sleep on exit bit, and then enter sleep mode.

ARM Architecture

SCB->SCR [1]= [2];
SCB->SCR [3]= SCB_SCR_SLEEPONEXIT_Msk;
asm volatile ("WFI");

Drag options to blanks, or click blank then click option'

A&

B~SCB_SCR_SLEEPDEEP_Msk

C|

DSCB_SCR_SLEEPDEEP_Msk

Attempts:

3 left

💡 Hint

Common Mistakes

Using OR to clear bits

Using AND without complement to clear bits

Mixing up bit masks

Clear the SLEEPDEEP bit using AND with its complement, then set SLEEPONEXIT using OR before WFI.