S7-300 Module Diagnostics S7 Pro v5.5

Hello all, first time, long time.

I'm new to the Siemens world and have latched on to a daunting project. I'm setting up an S7-300 plc with 2 remote IO racks and a WinCC Comfort HMI. For an added degree of difficulty it will also include having Software Redundancy.

My first question is, how do I set up module diagnostics? I have two IM-153s at each rack and will be using redundant IO. Rack 1 is primary while rack 2 is secondary. I need a way to determine the health status of each module and IO point so that I can use the logic to determine which IO point to use.

Unfortunately, this is not like the S7-400 so I don't think it can be done by simply using hardware redundancy.

Also, since I am using Software Redundancy, I have to use S7 Pro version 5.5 instead of TIA Portal. Please kindly advise if you have any pointers for me.

I cannot answer your question re diagnostics with a system based on S7-300 software redundancy. Just want to comment this.

S7-300 software redundancy has a very long switch-over time.
I investigated it once, and Siemens Support told me it could be up to 10-30 seconds. And it isnt much less expensive than S7-400H with hardware redundancy.
Because of that, S7-300 software redundancy is not used very much.

Do you happen to know the usual way of checking module diagnostics? I'm currently using OB86 and it will get called whenever there is a rack fault but I also need to the ability check for module faults and wire breaks.

Also, you are correct on the switchovers. It is not a very good system for CPU redundancy. After this module stuff, I need to work on getting my IP address to switchover when a CPU fails.

Look up the function of OB82, it will handle the diagnostic events.
Take a good look at using the S7-400H instead of software redundancy with the S7-300.

Thanks for the tip. I'll take a look at it in the morning when I get to the office.

Unfortnately, Im stuck with the S7-300 for this project. I will definitely not be using software redundancy again.

Section 13 in this manual goes through system Function Blocks for diagnostics.

https://www.automation.siemens.com/doconweb/pdf/SINUMERIK_SINAMICS_03_2013_E/S7_SFC.pdf?p=1

I should add section 33 describes diagnostic requests and messages

Does Report System Error not work in combination with the Software Redundancy? That's usually the first place I turn for module diagnostics.

I ended up looking at the status LEDs in the software. Kind of a backwards way of doing it but unfortunately the modules I bought did not have diagnostics built in and this was the only way to do it.