Processor Input Interrupt/PII PLC5

Hi,

May be somebody here know about PII (Processor Inputs Interrupt) on the AB PLC-5?
What function of this and when I can use PII?
Can somebody help?
Thanks

What is your question? A PII is a processor fault usually. What do you want to do with it?

I dunno....but

Here is a sample: http://domino.automation.rockwell.com/applications/kb/RAKB.nsf/0/E4C877661F7E33AF85256CD200778D66?OpenDocument

Greetings Deer,



if you already know how an STI (Selectable Timed Interrupt) works, then you’re more than halfway home to understanding a PII (Processor Input Interrupt) ...



you probably already know about this - but just in case, here’s the basic idea behind an STI:



the processor temporarily interrupts its program scan - and jumps over to the ladder file that you’ve set up as an STI file - and starts scanning there ... the processor does this “interrupt” at a time (a frequency) which you select and configure ... in other words, with an STI you tell the processor: “whatever you’re doing, and wherever you are in the scan, stop what you’re doing and go run the STI file instead ... then come back to where you were and finish the normal program scan” ... and the most important thing for our discussion is that you get to tell the processor how often to do this interrupt thing based on a TIME which you get to set ... secret handshake: STI is an “I”nterrupt to the program scan which takes place at a “T”ime that you get to “S”elect ...



STIs are fairly common ... now let’s talk about PIIs ... these are MUCH less common ... in fact, personally I’ve never seen one used in the real world ...



here’s the basic idea behind a PII:



the processor temporarily interrupts its program scan - and jumps over to the ladder file that you’ve set up as a PII file - and starts scanning there ... the processor does this interrupt whenever a certain input changes state ... and you get to select the input and configure whether a change from OFF-to-ON triggers the interrupt ... or whether a change from ON-to-OFF initiates the trigger action ... in other words, with a PII you tell the processor: “whatever you’re doing, and wherever you are in the scan, stop what you’re doing and go run the PII file instead ... then come back to where you were and finish the normal program scan” ... and the most important thing for our discussion is that you get to tell the processor how often to do this interrupt thing based on an INPUT changing state ... secret handshake: PII is an “I”nterrupt to the program scan which takes place when an “I”nput to the “P”rocessor changes state ...



so that’s the basic idea ... when do you use a PII? ... maybe for something like a very fast acting process ... something like a canning line where decisions have to be made very quickly - and a programmed output response needs to be taken very quickly ... there is more information about “when-to-use-it” and more details on PIIs in general starting on page 18-1 of this manual ...



finally ... note that the PII function is native to the PLC-5 platform and to RSLogix5 software ... for the SLC-500 platform and RSLogix500, take a look at the DII (Discrete Input Interrupt) ... but ... I’ve never seen one of those used in the real world either ...



I hope that this “basic idea” information is what you were looking for ... but if you need more detail, please post again ... I’ll be glad to give it another try ...

Thanks Ron,



If I am not wrong, this PII file will be execute when there is a change in input condition( let say change from OF to On) and the main program will be interrupted at the moment and run the PII file.

After PII complete execute,the processor run the main program again.Is it right?
And.. without PII, is it not possible that processor can execute a very fast process?

In the user manual, there is an example with a short explanation about PII in canning line, they say “you may need to counts inputs quickly to track production, such as in canning line”, Ron, could you give me explanation how this work?

Thanks for your time

If I am not wrong, this PII file will be execute when there is a change in input condition( let say change from OF to On)

Click to expand...

yes ... or you can also set it up to execute when there is a change from ON to OFF ... you get to choose ...

and the main program will be interrupted at the moment and run the PII file.

Click to expand...

yes ... exactly ...

After PII complete execute,the processor run the main program again.

Click to expand...

it would be more correct to say “After the PII completes its execution, the processor will go back and continue running the main program” ...



the difference: the way you said it, it sounds as if the processor will start the main program over again from the beginning ... that’s not correct ... the processor goes back to the same point in the main program where it left off ... specifically, the processor CONTINUES the main program ... it does not START IT AGAIN ...

And.. without PII, is it not possible that processor can execute a very fast process?

Click to expand...

certainly the PLC processor is very fast ... but the mechanics of some manufacturing systems might be moving VERY VERY VERY fast ... in this case, the scan time of the processor might be long enough to “miss” a certain important input ... as I said, I personally have never seen any process which actually required a PII ... but ... I don’t get around as much as some of our other members ... so I’m sure that there are some out there ...

In the user manual, there is an example with a short explanation about PII in canning line, they say “you may need to counts inputs quickly to track production, such as in canning line”, Ron, could you give me explanation how this work?

Click to expand...

I’ll be glad to try but it will be at least a day or so before I have time ... watch this thread and if no one else tackles it, I’ll do the best I can as soon as I get a chance ...



now just a few quick questions for you ... do you think that you might need to use a PII in a system that you’re working on? ... or are you just curious and trying to learn something new? ... and do you have a spare PLC-5 system to experiment with? ...

Ron,
Thanks again for your reply..
Basically, I don't need to use PII(I can use STI in many application), but just want to know what function of this.
At least right now I understood what function of this and when I should use this.
Thanks Ron..