YEAR 1 CO1 WEEK 24 INTERUPTS Flashcards
What are interrupts?
More efficient way of finding out whether device needs CPU time using an interrupt.
Interrupt is a signal indicating process of device needs attention.
What are two ways of dealing with events ?
Polling and interrupts
What is polling?
The purpose of the CPU is to process data and follow instructions. Also must be able to respond to events as they happen.
Polling checks device if it needs to do anything which is inefficient but is simple and predictable.
Advantages of polling?
Predictable and simple
Disadvantages of polling
Inefficient use of cpu
State the Interrupts Process.
If Interrupt level lower/ equal to current process current process continues.
If higher priority CPUs finishes current FDE cycle.
The contents of CPUs registers copied to stack in memory.
Location of appropriate interrupt service routine loaded into PC.
When ISR complete previous contents popped from stack and loaded back into registers.
What are priorities during interrupts?
If an interrupt arrives which is higher priority it will move the lower priority to a stack but if after that a lower priority appears it is told to wait then after that if the initial task is more important then it will take it out of stank and do that first or the other way round
What happens if the stack is full?
Stack over flow
What is ISR?
Interrupt service routine
What is a user interrupt?
A key press eg CTRL/ALT /DEL
What is a software interrupt
Run time error
I/O error
Printer out of paper
Hardware error
Out of battery waring
What are Higher order interrupts
Impending data loss
What is latency
Delay between input and desired output
