Simatic S7 - DataBlock data Lose !!!

biomorf

Member
Join Date
Jan 2007
Location
Kosice
Posts
12
Hello everybody,

I have strange problem. It is third time, that this think appeared. PLC worked fine with out problems and later for some unknown reason it lost every actual data in all DBs. I don't understand why is this happening.
You should know that it wasn't the same PLC and it wasn't every time my program :).
I was called this morning to solve this problem and I saw what happend. I call to mind that same think happen to my collegue whe we where in work trip in Rusia. So now I don't think that thit this is only fortuity.

What you think about it ???
 
If the data has reverted back to the "initial values" inserted when the DB was declared, this would suggest a cold reset has occurred for some reason.

What is occurring on the machine immediately before these "strange" happenings? Is the machine being powered off and then on again?

Does the DB have initial values that are not all zeros? Does the data revert to zero or some other number?

What type of CPU? Is there a battery backup?

A common cause of "unexplained" data loss is subsequent offline DB modifications, downloaded to the PLC, overwriting changes that were made by a VAT table. That is, the data was only current in the PLC, not the offline project, and it was overwritten by downloading the DB again.
 
Hi MartinW,

first thanks for fast reply.

DB's have initial values set to zero, so like you said the most possible reason is Cold Restart.
There was no modivication of DB's in offline. This mashine is running more then 10years without problem like this.
I know that Cold Restart can be done only manualy from PG. Is there an other way? Perheaps some power supoly drop???
In one case it was and old CPU 313 and in second it was new CPU 315. The second time didn't happend to me, so I don't know details.
 
The new CPU 315 would, I think, have a MMC card to keep non-volatile data on.

The older one might well have relied on a battery. But I think you would know if the battery was down, the program would have been lost also.

As you say, I think Cold restart is only initiated from the PG. If this "just happened" one day with no-one connected to or near the PLC I can't think of a cause. (Bear in mind that often what's reported as "it just happened" is often not the full story!:unsure:

Sounds like one for L D[AR] to comment on. Over to you Simon!
 
:) yes...

not full story...

for these I every time ask first : What you did with the machine :).

and the machine operators or servce man say... nothing :)


OK, thank you very much...
 

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