Non vectored interrupts

Question

http://superuser.com/questions/414290/when-a-non-vectored-interrupt-occurs-does-the-processor-ever-look-up-the-vector

In a non-vectored interrupt, the peripheral itself provides the address of the interrupt service routine directly to the processor. This requires more time for an interrupt to be serviced, since the address must be retrieved from the interrupting device every time the interrupt is triggered.

S ans is B??

In a non-vectored interrupt, the address of interrupt service routine is

• A. Obtained from interrupt address table.
  
• B. Supplied by the interrupting I/O device.
  
• C. Obtained through Vector address generator device.
  
• D. Assigned to a fixed memory location.
  
  • A. A
    
  • B. B
    
  • C. C
    
  • D. D
    
    Ans: D. D
    Ans Explanation :
    The source device that interrupted the processor supply the vector address which helps processor to find out the actual memory location where ISR is stored for the device.

Answer 1

Correct answer : (D)

In non-vectored interrupt, it is responsibility of CPU to find the address of ISR and to find the device which caused interrupt.Actually once CPU gets interrupt from a device, it completes its current execution phase and start servicing the interrupt. To do so,CPU first runs a default ISR, address of it is already known to CPU. Now this default service routine is stored somewhere in fixed memory location which CPU knows. So CPU refers to it and find the address of actual ISR from it & also address of the device which caused the interrupt. Actually CPU uses POLLING technique to find address of interrupt causing device.So once CPU gets address of ISR,it starts executing it and after completion it resumes its own execution.

Comments

The explanation abt non vectored interrupts in d above link is wrong??

In a non-vectored interrupt, the peripheral itself provides the address of the interrupt service routine directly to the processor.

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Yes,its wrong .

Please refer standard book : 1)hamacher - computer organization (5th ed)  page :213 -214

                                              2)Patterson, Hennessy - Computer Organization and Design Page  : 327

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Thank you :)

Answer 2

correct ans is D)

A non-vectored interrupt is where the interrupting device never sends an interrupt vector. An interrupt is received by the CPU, and it jumps the program counter to a fixed address inhardware.

Answer 3

option D

For Non-vectored Interrupt

1. When CPU gets the interrupt signal it loads the address of Default Service Routine(DSR) into PC.
2.  The DSR finds out which device have generated interrupt and the address of ISR.
3.  It then loads the ISR addess to PC to service the intrerrupt.