Interrupts

Question 1

What are Hardware interrupts?

Answer 1

Hardware interrupts occur when devices indicate they need attention; for example, mouse button pressed.

Question 2

What are Software interrupts?

Answer 2

Software interrupts occur when programs detect an error or illegal operation.

Question 3

What happens when an interrupt is generated?

Answer 3

When an interrupt is generated, the operating system executes an interrupt service routine; so, if the interrupt is high priority, it causes the fetch-execute cycle to be immediately interrupted after the completion of the current instruction

Question 4

What is a store interrupted task?

Answer 4

• Current instruction finishes its execution
• Program counter contents stored in memory
• Register contents stored in memory

Question 5

What is an Interrupt service routine carried out?

Answer 5

• Interrupt number examined and source of interrupt identified
• Program counter loaded with start address for interrupt service routine
• Interrupt service routine is executed

Question 6

What is a continue interrupt service?

Answer 6

• Contents of registers from original task restored to memory
• Program counter contents from original task restored
• Interrupted task continues

Question 7

What happens when a hardware or software interrupt is generated?

Answer 7

• When a hardware or software interrupt is generated, the processor checks the priority of the interrupt.
• If the interrupt is a higher priority than the current process, then it will be stopped at the completion of the current instruction to deal with the interrupt.
• Once the interrupt has been dealt with, the interpreted process continues until completion.