Interrupt priority levels in Embedded C - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an interrupt priority level in embedded systems?

An interrupt priority level is a number that tells the system which interrupt is more important. Higher priority interrupts can stop lower priority ones to be handled first.

beginner

Why do we use interrupt priority levels?

We use interrupt priority levels to manage multiple interrupts. This helps the system respond quickly to important events without ignoring less urgent ones.

intermediate

How does a higher priority interrupt affect a lower priority interrupt?

A higher priority interrupt can pause or 'preempt' a lower priority interrupt. The system handles the higher priority interrupt first, then returns to the lower one.

intermediate

In embedded C, how do you typically set interrupt priority levels?

You set interrupt priority levels using special registers or functions provided by the microcontroller's library, often by assigning a priority number to each interrupt source.

intermediate

What happens if two interrupts have the same priority level?

If two interrupts have the same priority, the system usually handles them in the order they occur or based on a fixed hardware scheme, but they do not preempt each other.

What does a higher interrupt priority level mean?

A It is ignored by the system

B It runs only after all lower priority interrupts

C It is handled before lower priority interrupts

D It disables all interrupts

Higher priority interrupts are handled first, preempting lower priority ones.

How are interrupt priorities usually assigned in embedded C?

A By writing interrupt code in a specific order

B By setting priority numbers in special registers

C By disabling interrupts globally

D By using delay loops

Interrupt priorities are set by assigning numbers in hardware registers or using library functions.

What happens if a lower priority interrupt is running and a higher priority interrupt occurs?

A The lower priority interrupt is paused and the higher priority interrupt runs

B The lower priority interrupt continues without interruption

C Both interrupts run at the same time

D The system crashes

Higher priority interrupts preempt lower priority ones to be handled first.

If two interrupts have the same priority, how does the system decide which to handle first?

A Usually by the order they occur or hardware scheme

B The system ignores both

C The system merges them into one interrupt

D The system randomly picks one

Same priority interrupts are handled in occurrence order or by fixed hardware rules.

Why is it important to assign correct interrupt priority levels?

A To disable all interrupts

B To slow down the system

C To avoid using interrupts

D To ensure critical tasks are handled quickly

Correct priorities help the system respond fast to important events.

Explain how interrupt priority levels help manage multiple interrupts in an embedded system.

Think about which interrupt runs first and how the system decides.

Describe how you would set interrupt priority levels in embedded C code.

Consider hardware registers or API calls.