Rslogix 5 help. How to know if a word is being used.

[mudcrutch89]

I have been using this forum for a while now and can usually find an answer to all of my questions, but this time I must ask.

I am using rslogix 5 with a Plc5/20 connected to a PanelView 1000 through DH+. I am trying to set up a new word to send a number to display on the screen. I can see that it is already using the N10 data file area for similar processes. My problem is that I have found two words that when viewed with radix = binary/subelement show that none of the bits are being used. But one word has an 'F' (word1) under the FW column and the other (word2) has nothing in that column. When viewed in the radix = Elemnt only mode word1 is shown as being used and word2 is shown as being unused. When i look at the data file, word1 has data (16533) and word2 has no data(0). However, when I do a global find both words have no results.
So finally, my question is... Can I use word1? or is it being used somewhere and I can't see it?

Any help would be great.

 

[Jtari89]

Cross Reference

"F" Means the FILE is being used somewhere in the program.
When looking at the usage right click on N:10(Whatever integer your looking for) and click cross reference. Don't think it will find anything with a "find all"

 

[harryting]

Be careful here. Using "find" in RSLogix doesn't necessary tells if the word(s) is used. You can have indexed array (N10:[N7:10]) or COPy command that copy a series of words (COP N7:0 N10:0 20 - copy N7:0 to N10:0 for 20 words).

Cross Reference is a better tool to use for such purpose. Also you can have instance where a message command on a remote PLC over-ride local PLC addresses but this shouldn't be a concern if this is the only PLC on a network.

You can also try put a number in the word and see if anything override it.

 

[geniusintraining]

Be careful here. Using "find" in RSLogix doesn't necessary tells if the word(s) is used.

Found that out the hard way..., mine was being wrote to the CPU from another CPU on a Data Highway Plus network and the person that wrote the code never added any comments saying where it was coming from, we had 12 nodes on the network and it was a guessing game to find out where it was coming from, not fun

 

[mudcrutch89]

Thanks everyone.
I did the cross reference on word1(N10:261) and word2(N10:262) and there was no result for either one.
Does this mean that word1 is safe to use?
If so, was the data that I saw in word1 from either some old logic or manually entered at some point?
I can't connect to the plc until saturday when I'm on site, so I can't try entering a number to see if it gets over written.

 

[geniusintraining]

Does this mean that word1 is safe to use?

How many nodes on the network other then the PanelView and your CPU?

 

[mudcrutch89]

The PLC is isolated. It is only connected to the panelview and of course the IO.

 

[geniusintraining]

I would think you should be OK, I have found that most of my issues came when they were hooked to a network and the data/word was be used (wrote to) from another CPU

 

[OkiePC]

You said word one has data and is shown as being used with an F marker, so it is being used as a file address somewhere in the logic. I have not had problems with the usage button looking at data files, but external MSG writes with no comments have been discovered by me too.

It is always possible to have windows puke down its leg.
http://www.plctalk.net/qanda/showthread.php?t=49181

I guess that could make the usage table view lie to you...check the speed of you communication spinner icon to make sure you are "talking" normally.

If RSLogix marked it with "F", and "update cross references" is turned on, word one is used.

You need to find it in the project and ensure that it is not part of some data area that will affect word two under the right conditions.

Before you use it, look at what you are sticking it in with. Since the only other device is a Panelview, look at the tag list for it as well.

If you still cannot find the FLL or COP or other file type of operation, try searching for "[" and see if there is indirect addressing that is causing data to be marked at used