Newbie Question AB PLC5

When downloading a program to a PLC what is difference between online editing and just downloading the program with changes that were made offline. My real question is I made a backup copy of the program in use and made changes offline now when i go to download the updated program back into the PLC will the processor hault while the updated program is being downloaded or will the processor and process keep running while downloading? Dont want to shutdown process while downloading new program.

Havent done anything to data files only ladder logic is changed.

If you download a a program it will put the PLC in program mode ( hault program scan) during the download.
Online edits can be done while the program is still running.
So if you don't want the process to stop then do online edits.
But be careful while doing online edits, changes take place
immediately.

Online editing allows you to make changes to the program while it is running. It's a pretty slick setup because you can edit a rung, and once you've accepted it, you can tell the processor to 'test edits' It will stop using the un-edited rung and start using the edited rung. If it doesn't work like you expect you can immediately disable test edits and keep working. If you like the test, then you can assemble it, removing the old rung and keeping the new one.

It's nifty things like this that make using a ML1000 a real headache.

monkeyhead said:

Online editing allows you to make changes to the program while it is running. It's a pretty slick setup because you can edit a rung, and once you've accepted it, you can tell the processor to 'test edits' It will stop using the un-edited rung and start using the edited rung. If it doesn't work like you expect you can immediately disable test edits and keep working. If you like the test, then you can assemble it, removing the old rung and keeping the new one.

Click to expand...

Is that also the case with a PLC5?

Yes, the PLC5 and SLC have the same online editing procedures.

You can insert rungs, modify rungs, delete rungs, and then test the edits all at once. Untest them if they need more work, and then assemble them when you want the changes to become permanent. Those edits can be scattered throughout the program in multiple ladder files.

Somewhere in the archives there is a good thread on the subject but I didn't have much luck when I searched for it.

Basically, when you insert a rung, at first that change only exists on your programming PC, not in the PLC. It will be identified by a lower case "i" on the power rails. Any edit that is marked by a lowercase letter is called a "ram rung edit", and only exists on your PC until you accept the edit. You can search for ram rung edits by searching for "^e" in the find function.

When you accept the inserted rung, it is sent to the PLC and those lower case "i" symbols will be replaced with uppercase "I". The PLC does not yet start using the inserted rung, but it has it in place and ready to go.

When you delete a rung, the rung will immediately be marked with an uppercase "D". Again, the rung is still there, and is still being scanned, but it is marked for deletion.

When you edit an existing rung, a copy of it will be made with the lowercase "e" next to the power rails, and the rung that is to be replaced with be marked with "r". When you accept your edits, the "e" changes to "I" and the "r" changes to "R", but the PLC is still scanning the rung that is marked for replacement, but has it flagged to be disabled when edits are tested.

You can search for all types of edits that exist in the PLC program by searching for "^a" in the find function.

Note that all during the process, lowercase power rails, means that the changes haven't been sent to the PLC, and uppercase letters on the power rails indicate that the changes have been sent to the PLC.

More importantly, the highlight (green by default) tells you which rungs are actually being scanned at any given time.

So, when you accept a rung, you are merely sending potential changes to the PLC. Nothing actually changes until you hit the Test Edits button. At that point, any "I" rungs will go active, and "D" rungs or "R" rungs will go inactive.

The original rungs will still be there, but the power rails will not be highlighted, instead, the edits, marked by "I", will be highlighted while edits are being tested.

When you untest edits, your test rungs are switched back off, and the original rungs are switched back in.

When you are satisfied with your edits while they are being tested, you can then assemble them to make the changes permanent, do away with the rungs that are marked for deletion, and remove the marks from the rungs that are now being run.

Paul

EDIT: I found a good Ron Beaufort post #17 in this thread:
http://forums.mrplc.com/index.php?showtopic=6785&st=0&p=27930&#entry27930