Old Siemens 314 EEPROM

[orense]

Hello,

One of my colleagues were at a plant were we have two old Siemens 314s running on identical seperate processes. He did a minor modification on both, but could not test it properly because the equipment was not operational.

Afterwards the customer is telling us that there is a false reading on one of the plcs. We suspect the my collegue forgot to load a network in the plc that has the reading failure.

To have this verified we swapped the EEPROM from the one working, rebooted power, but it was still faulty.
We swapped the cpus and the reading was ok. So, swapping cpus with same EEPROMs as when programs loaded, everything was ok. But not when using the EEPROM from the one working.

It tells us that when we swapped the EEPROMs, it can not have been using the program from the EEPROM working.

Therefore my question is: What is the proper way to boot from an EEPROM?

Does the 24 voltage have to be turned off over a certain period in order for the RAM to loose the previous program? Do we have to do any procedure with the operator key while there is no EEPROM in the cpu?

Any suggestions on this would be highly appreciated

brg
Andreas

 

[JesperMP]

I think that the memory is reset if the battery is removed and there is no MC card when powered down. Not sure if you have to wait for some time though.
It should be possible to do a memory reset by means of the keyswitch.
But I cannot find the exact procedure though. In the manual, it just says "a special sequence has to be followed". Doh ! Maybe it is the same as for S7-400 ?

You are not onsite, so you could investigate both offline and online programs ?

 

[orense]

Thanks Jesper,

That is the exact impression I got, and it is why I posted the thread.

We had similar issues earlier when batteries got old, and as these cpus will start to face problems in the "near" future, due to facing 10 - 15 years in rough enviroment, then I would like to have a certain procedure prepared.

You have the battery, you have the memory reset and the possiblity of keeping RAM memory for some time (even though not in theory), so there are some factors involved. If the manual is not clear, it will be speculation.

No, I am not onsite. I guess we have to do proper testing in the office...


brg
Andreas