Hi Rescobedo,

As with any software product, there is always the possibility of an error in the PLC. However, it may also be expected behavior in the particular situation.

I am not aware of any firmware or software bug that would explain the behavior described. But without knowing the details - in this case the PLC code - it's impossible to give a general answer. To clarify this, I would recommend that you contact Siemens and create a support request the next time you observe such a problem.

Kind regards
Stefan

A screenshot of the logic may help greatly.  Otherwise, we will be guessing.

It is usually because whatever code is required to reset a tag to false is inside a block that gets the ENable input turned OFF too soon, so that block does not get the opportunity to reset it to false.

Many Siemens PLC blocks with DBs associated with them require the EN to remain on pretty much all the time, or for as long as the block's InOuts and Output tags may need to change.

Rescobedo

Hello we had similar problem.

A variable was left in true state after the sequencer was no longer in the step that assigns to variable a true value.

Could this be a bug in the PLC itself?
the variable is not wrote anywhere else in the project and no overlapping happening, this is the second time it happens in 2 different machines.
the first time it happened happened in a
PLC: 6ES7 516-3FN02-0AB0
Firmware: V2.9

TIA V17

and most recently:

PLC is: 6ES7 516-3FN01-0AB0

with firmware: V2.6

Tia V15.1

Does somebody has more information about this?

Regards.

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Split from Problem with the operation of the program in "Graph" - action N is sometimes not executed.