7072 Communication problem

Some of my data is transmitting. One piece of data will send to the other device, but will then revert back to zero after about 10-20 sec. When that happens, our logic 5000 processor shows a fault for the Anybus. When that fault happens, status light one and two blink green 3-4 times.

The other problem is that the data for another integer never changes at all, but when a person read the log file for me, the anybus thinks it sent it. The manufacturer of the end device says it works fine on his end

Please share the log file and configuration file.

It sounds like there may be a communication problem between the PLC and the Anybus as well. Are they connected through a switch or directly? Is there long cabling involved or possible EMI?

What fault is shown in RSLogix 5000?

You can also find some troubleshooting tips in this article for troubleshooting the subnetwork problems:

I have an LED 5 error on my Anybus Communicator

The anybus is connected to our hub for the line about 3’ away. The only thing in this panel is an HMI, 24v power supply and the hub for several of our nearby Ethernet devices. The width of our film is communicating constantly and accurately. These failures happen every time.

In regards to the fault shown in the logic 5000, it just says faulted. This is shown in the tag database for the anybus tags

That article appears to be about a fault on LED 5. The lights that blink green for me are LED 1 and 2


We’re going to need more information to be able to help you.

To create the log, connect to the Anybus and go to Tools > Start Logging.

In RSLogix tree, right click on the AB7072 Module. Click on the Connection tab. Please take a screenshot of the area that says “Module Fault”.

I apologize for the title, but this article shows how to troubleshoot all types of subnetwork problems like:

Attached are the log files for the two different situations, the anybus setup files the pic of the fault. Let me know what else you need. I hope the log file was long enough for parameter 17. When I actually timed it, it takes between 1:20 – 1:50 for the parameter to change back to zero.


Changed Parameter 146 from 1 to 0 to 1.txt (31.3 KB)

Parameter 17 change back to 0.txt (31.2 KB)

Anybus with Auto Feature.cfx (1.42 KB)

Anybus with Auto Feature.cfg (16 KB)

Hello @stribout ,

I think you have the cause and effect backwards. Your first write commands aresetup to clear when the fieldbus (PLC) connection is lost, and the Read commands are set to freeze.

You will need to identify what is actually faulting, it sounds like the Communicator is acting as intended.

I would review the fault message the PLC is reporting. I would expect more info on the fault, possibly in the devices properties.

That took care of my parameter that is changing back to zero. It still faults periodically, but I don’t lose my data.

I’m still having no luck with my parameter 146. It still won’t change in our web guide. This was captured in one of the log files I sent last time. Any thoughts on that one?

Hi Stribout,

I am not sure exactly what you are asking me to look for. In the log a transaction setting the register to 0and later setting it to a 1. Both do not show modbus errors.

I was just trying to narrow down where the communication problem was. I saw the tag change in the logix 5000. The web guide controls guy said that his program works on his test stand. He was taking the problem was in the Anybus. But as far as you can tell, the Anybus sent the changed parameter to our web guide, correct? Assuming the parameter is correct. Is there anything else you can think of that would cause the changed parameter not to get to our web guide?


Yes it looks like the Communicator is working as expected. The Read requests are cyclically reading and the write requests are being send on change. In the log i see it get set to a 1 and a 0.