ONS vs OSR

For a Micrologix Instruction set, would you please tell me why to choose ONS vs OSR.
Is there something that the ONS can do that the OSR cannot? Or vice-versa?
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Here is what I already know.
Sort of YES. ONS is exclusively an INPUT, while OSR is exclusively an OUTPUT.
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IF I want an output to execute 1 time and only when a switch comes on then:
This single instruction
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--| Switch |-----| ONS |---------(output) ----
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Does the same thing as these 2 instructions
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--| Switch |--------------------------[ OSR B3:0/3 B3:0/4 ] ]--------
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---| b3:0/4 |-----------------------(output)

What situation makes ONS preferred over OSR?

narlin

OSR is good for Multiple Situations. One Shot Relay is placed in program once and you can use the one shot bit many times. ONS use is one time only. The next one you use needs a different address or tagname. ONS checks the status of logic preceding it in that rung Only. It looks for the false to true transition there. The OSR is a Relay you put your logic in front of and it acts like any other coil. The only difference, it is only true for one scan and must see the false to true transition before reacting the 2nd time.

I disagree with cwal61.

The inline oneshot instructions and those that are block instructions on their own output branch are functionally very similar, and you can use them in nearly exactly the same way.

How they are dealt with in pre-scan is the real difference and I think that's the reason that A/B gave them different names in different platforms.

http://www.plctalk.net/qanda/showpost.php?p=526030&postcount=10

http://www.mrplc.com/kb/index.php?page=index_v2&id=52&c=11

Narlin said:

For a Micrologix Instruction set, would you please tell me why to choose ONS vs OSR.
Is there something that the ONS can do that the OSR cannot? Or vice-versa?
What situation makes ONS preferred over OSR?

Click to expand...

OkiePC said:

The inline oneshot instructions and those that are block instructions on their own output branch are functionally very similar, and you can use them in nearly exactly the same way.

Click to expand...

How does this answer his question?

Disagree with What?

If you wish to enlighten the OP by your prescan, postscan expertise then I'm sure he will appreciate your enlightenment.

But that was not the question.

cwal61 said:

How does this answer his question?

Disagree with What?

Click to expand...

This:

OSR is good for Multiple Situations. One Shot Relay is placed in program once and you can use the one shot bit many times. ONS use is one time only. The next one you use needs a different address or tagname. ONS checks the status of logic preceding it in that rung Only. It looks for the false to true transition there. The OSR is a Relay you put your logic in front of and it acts like any other coil. The only difference, it is only true for one scan and must see the false to true transition before reacting the 2nd time.

Click to expand...

cwal61 said:

If you wish to enlighten the OP by your prescan, postscan expertise then I'm sure he will appreciate your enlightenment.

Click to expand...

Like I said, those are the functional differences that I know of. It's all explained in the links much better than I can do.

cwal61 said:

But that was not the question.

Click to expand...

I guess I could expand on my answer by stating (true story) I prefer the inline oneshot because it is prettier.

They work the same except for prescan. If that's important to you, make it the basis of your choice, otherwise, pick the prettiest one.

Some of the confusion may be that Allen Bradley in their infinite wisdom decided to make 2 different kinds of "OSR"'s for different PLC's. See PDF's below.

OkiePC said:

This:

OSR is good for Multiple Situations. One Shot Relay is placed in program once and you can use the one shot bit many times. ONS use is one time only. The next one you use needs a different address or tagname. ONS checks the status of logic preceding it in that rung Only. It looks for the false to true transition there. The OSR is a Relay you put your logic in front of and it acts like any other coil. The only difference, it is only true for one scan and must see the false to true transition before reacting the 2nd time.

Click to expand...

Click to expand...

Sorry, I got kicked offline and ran out of edit time. I meant to add that you seem to point out that the instructions are very different, while I find them very similar. I know what you are probably visualizing and I get what you meant, but I just didn't agree with how it's worded, especially that red part.

I apologize for any offense I caused.
Paul

Thanks for your explanation.

This is what I was Thinking. But This from 5000 Help. I thought 500 was worked the same but I could be wrong. I have not installed 500 projects in a few years.
I thought that the difference is you can use 1 OSR to do 10 one shot task and it would take 10 ONS to do the same amount of tasks.

ps. it's all good.