Originally Posted by Rohit Chatterjee

In IC 8085 there is a command RIM which is supposed to show u if any RST 7.5,6.5 or 5.5 interrupt is pending....Now what does "pending" interrupt mean???If the interrupts are disabled (either by masking or disabling the Interrupt Enable F/F) then the interrupts wont wrk at all....n if they r enabled,then as soon as the microprocessor is interrupted it will cease all current wrk n go respond to the interrupt....So either the interrupts are disabled or the microprocessor responds to them immediately....Where does this "pending" thing come into the picture????

hi,
Its all out there on Google;

Look at this explanation.
Interrupt Predictability

Originally Posted by Rohit Chatterjee

Thnx but the explanation went a few inches over my head....i mean its a bit hi-fi
.....anyone wth a simpler xplanation????

hi Rohit,
May I ask what subject you are studying and what year level you are currently at.?

This would help us to tailor our replies to suit your background knowledge,

Originally Posted by Rohit Chatterjee

In IC 8085 there is a command RIM which is supposed to show u if any RST 7.5,6.5 or 5.5 interrupt is pending....Now what does "pending" interrupt mean???If the interrupts are disabled (either by masking or disabling the Interrupt Enable F/F) then the interrupts wont wrk at all....n if they r enabled,then as soon as the microprocessor is interrupted it will cease all current wrk n go respond to the interrupt....So either the interrupts are disabled or the microprocessor responds to them immediately....Where does this "pending" thing come into the picture????

Pending is what happens when the conditions for generating an interrupt are present. An interrupt can remain pending for a variety of reasons including:

1. The processor is currently processing a higher priority interrupt.
2. The interrupt of interest is currently masked.
3. Interrupts are disabled.

You want the interrupt to remain "pending" until the processor can free itself from its other tasks and process the interrupt. That's what "pending" is all about.

Originally Posted by Rohit Chatterjee

M studyin electronics n telecomm engg....into my 3rd yr (5th semester)...n we hav this paper on IC-8085.....actually its on microprocessors wth 8085 as the case study....

Consider the word 'pending', it means the next action in a queue.

So if only one Interrupt is requested the programme will service the requested interrupt and then resume the next program instruction in the original sequence before the interrupt occurred.

If a second interrupt occurs while the mcu is servicing the first interrupt then the mcu 'notes' the interrupt but completes its current interrupt service, when done it will action the 'pending' interrupt, complete that, then return to the original program.

No. Interrupts can always remain pending as long as the peripheral device requires service. It does not matter what the processor is doing. When the processor gets around to enabling interrupts all those pending interrupts will be ready to go and the highest priority pending interrupt is the one that will be next in line for service.

The crucial point is that a peripheral device is responsible for maintining the interrupt in a pending status until it is serviced by the processor. This is one reason why level sensitive interrupts are preferred by some designers and programmers.