All CPU LEDs Blinking and OB1

Dear all,

Lately I’d an “All LEDs blinking” problem on several 315-2PN/DP’s in my project. Well, “problem”, I prefer to talk about “challenge”.

As I looked in the online diagnostics and several forums all symptoms were the same as other programmers experienced (DEFECTIVE: internal system error, memory problem, etc.) except for one thing: My CPU’s were crashing while I start monitoring OB1. It was possible to make changes to this OB and download it to the CPU without any errors.

I did all the regular things like: new MMC, update to the latest firmware and even replaced the CPU for a brand new one. All without any positive result.

While I was investigating OB1, I discovered that all the code which uses temp variables in OB1 were causing the error. By switching off these lines of code everything stayed normal. For my program this was not the solution, I needed these lines of code.

The call of the system diagnostic block was causing the error too so I switched this function off in the CPU’s hw config. After compiling and downloading I still had no positive result.

Finally, I decided to copy all the (SCL) code, removed OB1, inserted a new OB1, pasted the code back and downloaded it to the CPU. Now everything is back to normal.  For me this is very funny and I don’t have an explanation for it. I wasn’t using the system diagnostic in my program so no “problem” and no more “chalange”.

Regards,
Alex

Hi,

I would like to know if there was any modification on the Temp variables in "Faulty" OB1.

MicroMan

I would like to know if there was any modification on the Temp variables in "Faulty" OB1.

Hello Microman,

No, not even one. First I copied the SCL code to the clipboard and than I copied the OB to another (empty, offline, dummy) PLC. Deleted the corrupt OB from my project, made a new one, pasted the code back from the clipboard and copy-pasted the variables back from the dummy.

The variables (3 pcs) are not so special. Just Integers to store return values for block moves and system date & time.

And by the way: TIA V13 SP1 Upd9.

Regards,

Alex 

New question published by AliSoltani is split to a separate thread with the subject s7-300c-2dp, all LEDs blinking and can't connect PLC to PC.

Best regards
Min_Moderator