SIEMENS S5 - Programming port damaged !!

[ayman metwally]

Dear Sirs
I have a major problem that I have a SIEMENS S5 (928-135 u) and I cannot make any communications with this mentioned CPU through the programming port.
Actually iam using an OPC server that talks to the programming port (AS511 protocol)for a SCADA application.

It worked fine for about a weak.

Now I cannot communicate with the CPU. So (for trouble shooting) I connected the PG directly to the programming port in the CPU but still there is no communications.
So now i cannot program the PLC .. what a nightmare !!

Please note the following:
1- The PLC now is running normally and acquiring data through it's input cards and sending orders through the output cards, So there is no probability that the PLC is not working.
2- I used two PG units for testing and they are working fine with other PLCs.
3- Cables are also fine as I tested it with other PLCs.


So for now I think that the programming port is damaged.(Am I right??)
Is there are any other probability ??

I am asking you for advises as I do not know what to do (This PLC is in a Power plant so I am having hard time searching for a solution)

Thanks in advance

[JesperMP]

I think that to find out what is wrong you must prepare yourself to shut down the PLC. Hopefully you can do that without stopping the proces, or you can wait for a time where it is the least annoying.

I would then proceed like this:

1. Shut down the PLC and power it up again. If that fixes the problem, then the port was "hanging" electrically in a state it couldnt get out of. Maybe caused by electrical noise or voltage differences over the connection.

2. If 1. doesnt clear the problem, then reset the CPU and load the program from the memory card (if there is a memory card !). If this clears the problem then the port had been reconfigured in some way so it no longer matched your programming or HMI settings. Maybe caused by your HMI writing to some address that it should not.

3. If 1. and 2. doesnt clear the problem, then exchange the CPU. Consider to use a CPU with 2 PG ports, and to install overvoltage suppressors.

Good luck.

[ayman metwally]

Thank you MrJesperMP for your reply,I apperciate that from you .

Procedure no.1 worked out and every thing is going fine right now.

Actullly i was thinking of this but i was feeling bad saying to my self :what will "shutting down and powering the PLC up" do in my situation ?

Now i konw, It did alot.

Thanks againg for your help.

Ayman