SF Led stays on even without errors?

I'm testing DP diagnostic using the FB 125 block from siemens. I got it working and also the ASI network can be diagnosed via this block. So far so good.

Later I noticed that the SF Led on my CPU317-2DP PLC was on. So I checked the module information/diagnostic buffer of the plc. Strangly there were no new messages. When I press the update button there are no new messages. So in my book that means there are no problems.

In the end I switched the plc from run to stop and back again to run. The SF wend off. Does anybody have a clue what this can be?

I believe i've seen a simulair topic by RMA but coudn't find it..

Werner,

Were you doing any program changes prior to the SF LED coming on?

I'm not one hundred percent sure about this but would the SF LED come on if there was a problem with other modules attached to the main 317 PLC?

If so, (again I'm not sure at all about this) I think the diagnostic buffer of the 317 wouldn't reflect the fault as it wouldn't be local to that PLC. You'd have to interrogate the diagnostic buffer of the faulty module.

Did you go to "Diagnose Hardware" and see which module(s) were faulty on the network when the SF led was on?

I'm just plucking things out of the air here so may be talking brown stuff.... but it was just an idea that came to me after reading your post.

Cheers

JT

PS. Other than that, the fact that the fault cleared when you stopped and started the PLC might suggest yer commoner garden variety of gremlin...

Sorry to disappoint, but I haven't posted anything similar (as far as I can remember).

However, I have also noticed that the SF LED is on on my 317-2 DP (at least sometimes) although I have disabled all the DP-Slaves that are not present. Having said that, I do have about 10 errors in the diagnostic buffer, that I haven't been able to track down and they may be reponsible for the SF LED. Maybe it's another 317 funny?

The situation started to happen when my profibus network timed out due to frequency inverters without shielded cables being started. Once we found and solved the problem the SF stayed on. In the diagnostic buffer I've got loads of DP station failure and return messages. I'll keep an eye on it maybe the problem is gone? (I hope). At least the plc and program continue to work but it's annoying to have the SF led on.

Thanks for the reply!