Afi's

showshocka

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Join Date
Mar 2011
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USA
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510
Good morning all. I'm just curious of what the use of using an Always false instruction (AFI) if the rung will never be true anyway? The best I could come up with is for T/S, but I see lots of projects with theses instructions. I'm sure people in the past was not that careless to leave these T/S rungs in the project.
 
Don't be so sure that they weren't careless.

Also, I've used them in the past when I had code that either had to be taken out for a temporary basis (that usually becomes permanent) or had not actually been implemented yet.

I've done stuff like special sorting or rejecting that needs to be done only once in a while and I've used bits like AFI to diable the code.
 
There is a rather lengthy thread on this topic from a while ago that opened up a big can of worms.

Personally I use them to disable code that I want to de-activate, but not recreate in the distant future. I use bit addresses with descriptions to temporarily disable logic.
 
There is a rather lengthy thread on this topic from a while ago that opened up a big can of worms.

Personally I use them to disable code that I want to de-activate, but not recreate in the distant future. I use bit addresses with descriptions to temporarily disable logic.

Be careful here a "AFI" does not disable the rung. See links below

http://www.plctalk.net/qanda/showpost.php?p=8258&postcount=3

http://www.plctalk.net/qanda/showpost.php?p=337526&postcount=6


What is "T/S"?
 
Be careful here a "AFI" does not disable the rung.

You're correct, it does not disable the rung, it turns it false. When I leave logic for later use I like to still keep control of it (by scanning it), so I do not jump around it, or put it in un-scanned files, unlike some of my colleagues...
 

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