plc reaction, when reading none existing variable from plc

32/64 bit multi-platform Ethernet S7 PLC communication suite

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plc reaction, when reading none existing variable from plc

Forum: General Discussion

Creator: Michael Taxis

Created: 2015-08-05

Updated: 2015-08-05

Michael Taxis - 2015-08-05

Hi Davide,

At the moment I'm trying to program some kind of data acquisition tool, that reads from PLC ( using PLCSIM and nettoplcsim for testing, and S7-400 at a customer installation) and records to a file. I'm wondering what will be the reaction of the PLC, when I try to read a variable that does not exist, e.g. an input or output that is not in HW config or a DB that does not exist. Will PLC go into stop? I wanted to clarify this before using it at a life installation.

Thanks
Michael

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Davide Nardella - 2015-08-05

No, the function will report an error of resource not available but the plc work is not affected at all.

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Michael Taxis - 2017-06-02

Hi,
I have created the abobe mentioned acquisition tool, it is available on https://github.com/franzhefekranz/aqserver . It is only a console app that is writing to csv-file. For (live) visualisation I am using Kst2 from https://kst-plot.kde.org/ . It is possible to start multiple instances of the program to record from multiple PLCs at the same time. Program is open source under LGPL. I have used this on several installations running / recording for several days without problems. But of course use on your own responsibility.

regards
Michael

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