Interrupts

Question 1

define overflow

Answer 1

when there are not enough bits for a large number so it appears as 0

Question 2

What is the interrupt enable register?

Answer 2

this register is respobsible for enabling/disabling the interrupt.

Question 3

What is the purpose of interrupts?

Answer 3

A method of communication to request an action

Question 4

What is used to implement an interrupt?

Answer 4

-Interrupt vector table IVT
-Interrupt service routine ISR
-Interrupt enable/mask

Question 5

How is an interrupt enabled?

Answer 5

Enable an interrupt
-low on one of the interrupt ports
-go to address in IVT
-execute code at address (RETI - return from interrupt)
-retrieve the stored address for next instruction

Question 6

How do timer/counter interrupts work?

Answer 6

-When timer is enabled, clock cycles are counted and sends an interrupt when specific value or overflow

Question 7

What are the 3 main stages of interrupts?

Answer 7

-Find interrupt in IVT
-write interrupt service routine in the vector
-enable interrupt

Question 8

What are the 3 actions when an interrupt occurs?

Answer 8

-Program state is saved
-Microcontroller jumps to ISR in the IVT
-RETI

Question 9

Define polling

Answer 9

-microcontroller continuously checks to the status checks the status of another device to determine if it needs attention
-easy to implement

Question 10

What is the difference between polling and interrupts?

Answer 10

-Polling continuosly checks for status updates which is inefficient
-Interrupts are signals sent to the microcontroller to indicate it needs attention which is efficient but complex to implement (we need ISR, IVT etc)

Question 11

What are advantages of interrupts?

Answer 11

-interrupts solve problems quickly
-improve systems robustness and reliability

Question 12

What are disadvantages of interrupts?

Answer 12

-The number of interrupts is limited by external input pins
-response time to an interrupt might affect real-time applications where reliable response times are essential
(i.e having to repsond to an interrupt in the middle of doing a task)

Question 13

Define the interrupt vector table (IVT)

Answer 13

The addresses of different interrupt service routines (ISRs) are stored in the IVT

Question 14

What do the memory addresses in the IVT signify?

Answer 14

-the memory addresses of each ISR points to the program memory linked to each ISR start