siemens s7-318-dp

I had a strange thing happen this afternoon. One node on the Profibus circuit blew a fuse on the communications. After replacing the fuse, the processor apparently lost its memory and reset. No one will own up to turnining the key switch. Is there anyway to clear memory through a profibus fault?

Thanks,

Glenn

Hello!

What was the reason for the fuse to blow?

I have lost programs on a Siemens 300 series plc after a powerglitch or power failure. The memory have sometimes been messed up so I had to do a memory reset before being able to download.

I have also seen that the program was apperently ok in the plc (I was able to see it), but for some reson it did not run.
To fix this I had to do the following:
1. Copy the online program to the pc (not just upload, but going online and copying the program then pasting it to a new s7 program)
2. Verify the copy.
3. Reset plc memory.
4. Download the online copy (performed in step 1) to the plc.

The plc worked fine after doing thoose steps.

Hope this gives you some ideas...

Reagards
Borte

Hello!
Do you mean the Profibus card lost it´s memory?
In some of the profibus cards you can select where you store the
profibus card parametrization, if you select CPU then the card will get it´s data from the CPU when you start the system.
If the data is stored in the communication card then the data will be lost if you eg. change the card. (blow fuses etc.)

br. niklas

Sorry for the delay in replying, but I have been away on a much needed vacation.

One of the nodes (a pnuemax solenoid bank) blew a fuse that caused the power to the node to be lost. Upon replacing the fuse, when the node was restored the processor apparently scrambled/lost its memory. When trying to connect directly on the MPI it showed only a small portion of memory being used. After reloading all of the program the system came back up running fine.

We checked the battery for the processor and it appears to be fine.

Not a very comforting feeling to have a processer lose its memory.

I worked at a plant that had some serious power problems that would hit in the afternoon, each time it happened the Siemens S7-300's on our paper converters would either go bad or lose their program. Some of the OP7's were also affected.

We never did find out the real cause of the power glitches but it seems other plants in the area had the same problem. I had to replace several S7 300's and/or restore the programs.

I have also seen this happen with AB PLC5 and SLC500.

Hello!
Are you sure that the program was lost?
Have you programmed the fault OB:s eg ob86, ob122 ?
Maybe the program went into stop mode and somebody reseted the cpu ?
I personally have never seen that the program would disappeared.
Maybe copy Ram to Rom would help in this situation, then the program would be in the memory card not just the battery backed up memory?

I have seen this happen a few times at one of the plants I worked at. Suddenly, the program would become corrupt, and the only way I could recover was by pulling the memory card and battery, powering down, and downloading the program from scratch. I couldn't look at the diagnostics because the memory was completely scrambled.

Finally, I figured out what it was: The PLCs were networked together via MPI and connected to a modem for dial-in support. Apparently, some kind of voltage spike was coming in on the phone line, and it played havoc with that particular PLC. So, since I could support it by a RAS dial-up instead, I just disconnected the entire MPI network and it has been fine ever since.

S7Guy,
did you use a 'regular' modem, or did you use an industrial modem ?
I am thinking if a galvanic isolation between the phone line and the MPI network could have done the trick.

Did you use a Serial/MPI-converter ?
I think that there is a galvanic isolation between the buses?

The hardware was already in place before I was involved, but I am sure it was an industrial modem. I agree that it shouldn't have happened, but I ended up with a scrambled CPU once a month for a year until I finally disconnected it. Since I didn't need the MPI network and modem, I didn't investigate it further.