S7 - 300 Series CPU crashes on failed DP despite presence of OB85/86 etc.

[JesperMP]

It says that it stopped on "time-error" (OB80).
Dont you have OB80 programmed ?

It is confusing that the diagnostics buffer says something about "buffer overrun", whereas the online help mentions "exceeding the cycle time" and "acknowledgement error when executing an OB".
I am not sure how to interpret this.

It is possible that the STOP is caused by cycle-time overrun. And this can be explained by multiple calls to OB85.
I have had this error myself. Checking time online revealed an excessive last cycletime (+500 ms). It was with OB85 callup set to every single erronous i/o call.
You have it set to "only for coming and going errors" (I think).
This doesnt help at all, because all the i/o errors happen at the same time.

You may have to program OB80.
Obviously doing so will mean that you are accepting an extremely long cycle time, for a limited period of course.

If programming OB80 doesnt fix the problem, then you may have to consider your options again.
You could think about selecting "no OB85 callup".
To catch errors, you could add a check with FC125 before you start each step of your sequence.

 

[RMA]

OB80 is present, but apart from setting a Flag to kick off FC125, it's not doing anything else.

Originally, before I modified the program to switch off the interrupts inside the OBs, it was cycle time over-run which was causing the problem, however that was not the case here - maximum cycle time was 11 ms. As you suspect, I have OB85 set to "only for coming and going errors".

 

[JesperMP]

OK, cycle-time overrun is definitely ruled out (like you have said before).

It sounds like the many calls to OB85 conflicts with interrupt OBs.
The text "Mehrfacher OB-Anforderungsfehler verursachte einen internen Puffer-Überlauf" could be interpreted as saying something in that direction.

As you have FC125 in OB86 it should give you the same functionality as having OB85 active.
It gives you a system alarm that a node went missing, and it tells you which node it is.
It would be interesting to know if disabling OB85 fixes the CPU fault problem, even if you dont want to do like that in the long run.

 

[RMA]

OK, I'll give that a try, as you say, OB86 always comes as well as OB85, so that will ensure FC125 runs.

I expect it will be tomorrow before I get another chance to start switching the power on and off frequently, hopefully I'll stilll have Internet access then!

 

[hmiguel]

PLC S7-300 write in Page Excel

I wonder if it is possible to write a reading in PLC S7-300 on a page from Excel.
If it is not possible I would like to know which program should I use to be able to read values written to PLC S7-300 and relocate it on the PC.