PLC5 disappearing data trick

RonJohn · Mar 19, 2014

I have a customer with a PLC5/40 (series E, rev. J, for those of you scoring at home). They sent me a copy of their running program. Using RSLogix5, I added 10 data table files and a ladder file to their program so as not to disrupt any existing data/ladder files. The edited program was sent back to them for reinstallation.

The customer didn't download my copy of the program because they had recently made changes that I didn't have. Instead, they copied the new files into their offline program and downloaded to the PLC.

Something in the way they did this copy/paste caused nearly all of the data table registers to reset to 0. Needless to say, there was much consternation at the plant when the PLC was switched back to RUN mode!

I was able to duplicate this issue with my program offline, but I cannot explain why it happened. The only thing I can guess is that copying and pasting a Program File possibly overwrote the data table memory, but I'm not sure why this would occur.

Back in the day, I did a lot of work with PLC5. Those days are gone but I don't recall this happening anytime before. Can somebody offer up a clue as to what's going on?

Thanks in advance.

harryting · Mar 19, 2014

I have a bit of problem following the event but in any case, a quick way to fix it would be to do a partial download of the data file only from an archived copy with all the data value intact.

Bit_Bucket_07 · Mar 19, 2014

RonJohn said:
I have a customer with a PLC5/40 (series E, rev. J, for those of you scoring at home). They sent me a copy of their running program. Using RSLogix5, I added 10 data table files and a ladder file to their program so as not to disrupt any existing data/ladder files. The edited program was sent back to them for reinstallation.

The customer didn't download my copy of the program because they had recently made changes that I didn't have. Instead, they copied the new files into their offline program and downloaded to the PLC.

Something in the way they did this copy/paste caused nearly all of the data table registers to reset to 0. Needless to say, there was much consternation at the plant when the PLC was switched back to RUN mode!

I was able to duplicate this issue with my program offline, but I cannot explain why it happened. The only thing I can guess is that copying and pasting a Program File possibly overwrote the data table memory, but I'm not sure why this would occur.

Back in the day, I did a lot of work with PLC5. Those days are gone but I don't recall this happening anytime before. Can somebody offer up a clue as to what's going on?

Thanks in advance.

Their offline version of the program apparently hadn't had it's data file information updated when it was saved. This is optional, and it takes longer than merely saving the logic. It would have been safer for them to copy and paste the new program additions in online mode. That might have required stopping the processor and expanding some data files beforehand, but it wouldn't have required a download.

Bit_Bucket_07 · Mar 19, 2014

RonJohn said:
I was able to duplicate this issue with my program offline, but I cannot explain why it happened. The only thing I can guess is that copying and pasting a Program File possibly overwrote the data table memory, but I'm not sure why this would occur.

Do you mean that you saw data existing in files that was subsequently cleared when you pasted new logic into the program? I've never seen that happen.

RonJohn · Mar 20, 2014

Bit_Bucket_07 said:
Do you mean that you saw data existing in files that was subsequently cleared when you pasted new logic into the program? I've never seen that happen.

That's exactly what I mean. I tried to be concise in my original explanation, but here's more background.

I was charged with making the same additions to four different PLC5 programs. I created several new data tables in each PLC. I used the same data table designation (N60, T61, ST62, etc.) in each. I had to use different ladder file numbers in each PLC, but the logic was exactly the same.

I started with a running copy of each PLC program with valid data in T4, C5, etc. I made the mods to the first PLC. Next, I created new data tables in each PLC and then copy/pasted the data files & the program file into the other PLC offline programs.

I cannot say for certain when the data corruption occurred on my end as I was not looking at the other program/data files other than the ones I added. When the customer called me with his issue, I looked at my offline copy that I edited and noticed the same zeroed data. This PLC program is the only one where it occurred. This leads me to think something in that particular program was a factor.

Even though my data was corrupt, the customer didn’t download my program into the PLC because he had made other edits online concurrent with mine. My understanding of the customer’s actions is that he uploaded his running program, did an offline copy/paste of the new ladder file I created (rather than a partial download) and then downloaded the whole program when the data zeroing occurred. I believe he added the new data tables earlier, but that info is sketchy.

Everything is up and running once again, so I can’t burn much more time chasing this down. It just bothers me that a similar issue occurred twice in different instances with the same PLC and I’m still scratching my head.

Thanks for your patience.

PLC5 disappearing data trick

RonJohn

Lifetime Supporting Member

harryting

Lifetime Supporting Member

Bit_Bucket_07

Member

Bit_Bucket_07

Member

RonJohn

Lifetime Supporting Member

Similar Topics