I/O access error on S7-300

[aamirawan91]

Hi Siemens guys!

I am experiencing SF fault on our S7-300 (6ES7 315-2AH14-0AB0) CPU from time to time. I've checked the diagnostic buffer and found the following important events:

Event 8 of 10: Event ID 16# 2943
I/O access error, writing
P area, word access, Access address: 322
Requested OB: I/O access error OB (OB122)
OB not found, or disabled, or cannot be started in the in the current operating mode
External error, Incoming event


And

Event 7 of 10: Event ID 16# 4563
STOP caused by I/O access error (OB not loaded or not possible, or no FRB)
FC number: 106
Module address: 264
Previous operating mode: RUN
Requested operating mode: STOP (internal)
Internal error, Incoming event


Event 8 is pointed out the address 322 which is an analog output PQW322. I have checked it in the program and it seems to be fine there. Finally i replaced the analog output module containing this address but the issue still persists and sometimes the error is about another address PQW320 which is also in this module. Replacing the module didn't help. I know that adding OB122 will prevent the cpu from stopping but i don't want that. I want the cpu to stop when the issue occurs. I want to eliminiate the root cause of it but can't find the problem. I am attaching the diagnostic buffer here. Please have a look. Is there anyway i can attach the program here too? It's 1.05 mbs.

 

[JesperMP]

What kind of module is PQW320/PQW322 ?
Is it in the central rack or on Profibus or Profinet ?
Since no other significant entries appear in the diagnostics buffer, and you have replaced the module already, I think of these possible causes:

1. Backplane problem. It could be terminal modules are not properly connected, or the terminal module is defective. Or termination module is not properly connected.
2. Problem on neighboring module manifests on PQW320/PQW322 module..

 

[aamirawan91]

What kind of module is PQW320/PQW322 ?
Is it in the central rack or on Profibus or Profinet ?
Since no other significant entries appear in the diagnostics buffer, and you have replaced the module already, I think of these possible causes:

1. Backplane problem. It could be terminal modules are not properly connected, or the terminal module is defective. Or termination module is not properly connected.
2. Problem on neighboring module manifests on PQW320/PQW322 module..

Hi JesperMP

It's an analog output module: 332-5HF00-0AB0. It's the very last module. It's been replaced but the issue still persists. I have checked the addresses associated with the errors in the program and they seemed to be correctly programmed and configured. I am attaching the HW configuration picture for you.

 

[JesperMP]

Try swapping the U-shaped connector between the modules.

edit: If the wiring permits, you can also try to swap the 2 last modules in the hardware configuration, and also swap them in real life.

 

[aamirawan91]

Try swapping the U-shaped connector between the modules.

The "back connector" which connects one module to the next?

 

[JesperMP]

yes

 

[Ken Moore]

Jesper is assuming you do not have active back plane adapters. The Active backplane adapter, which allows you to replace modules midway, without stopping the modules further down stream, could be faulty. If you have an active backplane, reseating sometimes works on older systems.
These are common in industries that cannot tolerate shutting down an entire rack for one module swap. The most common method is to use "U" shaped connecters from one module to the next, in a daisy chain.

 

[JesperMP]

I might be wrong, but AFAIK the active backplane is only used when ET200M modules are in a redundant Profibus system with an S7-400H as Profibus master.

 

[aamirawan91]

Jesper is right. We don't have active back plain adapters.

 

[aamirawan91]

Update: So, finally I decided to add OB122 to prevent CPU stoppages from time to time but it didn't help. The CPU still stopped after some time and this time due to this:

Event ID 16# 4548
STOP due to I/O management

And right before this event all the events were about IO access error related to all the analog outputs of the last and only analog output module i have. Diagnostic buffer is attached.

 

[mk42]

Update: So, finally I decided to add OB122 to prevent CPU stoppages from time to time but it didn't help. The CPU still stopped after some time and this time due to this:

Event ID 16# 4548
STOP due to I/O management

And right before this event all the events were about IO access error related to all the analog outputs of the last and only analog output module i have. Diagnostic buffer is attached.

SIOS

support.industry.siemens.com

The FAQ above makes it sound like the message above means there's a backplane error, perhaps low voltage. Agree with the "swap modules and backplane connectors around" plan, to see if that helps.

 

[Ken Moore]

I might be wrong, but AFAIK the active backplane is only used when ET200M modules are in a redundant Profibus system with an S7-400H as Profibus master.

Wrong. I have seen active backplane on many stand alone S7-300 systems, usually continuous processes, such as chemicals, waste treatment plants and such, any process that required high availability. It is expensive, so not common.

 

[JesperMP]

Wrong. I have seen active backplane on many stand alone S7-300 systems, usually continuous processes, such as chemicals, waste treatment plants and such, any process that required high availability. It is expensive, so not common.

Was that with so-called software redundancy ?

 

[JesperMP]

Update: So, finally I decided to add OB122 to prevent CPU stoppages from time to time but it didn't help. The CPU still stopped after some time and this time due to this:

Event ID 16# 4548
STOP due to I/O management

And right before this event all the events were about IO access error related to all the analog outputs of the last and only analog output module i have. Diagnostic buffer is attached.

All of that tells us what we already know: The CPU cannot access PQW320 or PQW322 sometimes.

Please try what was suggested in #4.