Siemens S7 400 OB85 trouble

I am not very familiar with S7 so maybe someone can help me out. We had a problem last night with an OB85 I/O failure fault that seemed to correct itself other than the OB85 not resetting. All I/O works fine so we ended up removing a bit from the logic that the OB85 was holding from working. Does this have to be manually reset in the logic? Or will the OB85 reset when conditions permit?

OB85 not only detects I/O faults, but also Programm faults such as non-existant Blocks being called or missing IDBs. To identify the fault you need to examine the local information in OB85.

To help you we need a bit more information and preferably screen dumps and source code.

Daer Siemens,
The operating system of the CPU calls OB85 (if loaded)or goes to stop if OB85 not loaded in PLC:

• When a start event for an interrupt OB exists but the OB cannot be executed because it has not been downloaded to the CPU.
• When an error occurs accessing the instance data block of a system function block.
• When an error occurs updating the process image table (module does not exist or defective).

You can observe what happen by exporting value in OB85 into an MB (programmed inside OB85)

ex:

L OB85_FLT_ID ----> this is the error code
T MB800

then you can see what in MB 800, (possible values: B#16#A1, B#16#A2, B#16#A3, B#16#B1, B#16#B2, B#16#B3, B#16#B4)

The meaning of each code can be read in step7 by pressing F1 in OB85

Regards,

Anton

Thanks Guys,
I return to work Tuesday and I will look at OB85 again and see if the error codes are still there. From what I am hering, they should be.
Thanks,
101

Anton,
Can you tell me a little more about the export and MB thing. I am an s5 guy and this is all new to me. What is MB? And in your example is that a load and transfer (L,T)?
Thanks,
101

MB = Marker Byte (8 internal flag bits)

L (LOAD) and T (TRANSFER) are just as you would find them in S5.

Dear Siemens,
S5 FY = S7 MB
Please download S5-S7 conversion from siemens https://support.automation.siemens....tandard&viewreg=WW&objid=10805384&treeLang=en

You can use S5 STL for L and T statement in S7
Put it in OB 85 and check it while online using variable table, I recommend to put the byte into a MB retentive area (must set MB retentive range in CPU properties) and no FC/FB access that byte except OB85. If you find difficulties to set retentive area just create a DB and put it in (usually DB is retentive).
The reason are the byte value won't change except by OB85(OB85 is only called when error happen) or zeroed upon power-off

Ex:
L OB85_FLT_ID
T DB100.DBB0

Then you type in vareiable table DB100.DBB0 and watch online
I believe, if you experienced in S5, S7 will be a piece of cake for you.

Regards,

Anton