AB7072 Subnetwork Configuration Read Input Registers

I am using a the 7072 to communicate between a device utilizing Modbus RTU and a HMI running Ignition. The issue I have is getting the reading input registers commands to return data from device. In Node Monitor the input registers I am querying return zeros. I am able to use the Node Monitor and send a read input register command. I receive back the correct data from the device.

What is the difference between the Node Monitor and the subnetwork configuration read input registers command? There must be a setting that I am missing or setting incorrectly in the AB.

Thank you for your help.

Hi @kstingle,

Are you referring to the AB7072?

I am going to need some more details about what you’re doing in order to help. Can you send me your config file (.cfg) and maybe take a screen shot of what you are putting in the Node monitor? Also, if you have the memory map or user manual for the Modbus slave(s), that would be very helpful.



Sorry, Yes, the AB7072

Here is the cfg file and a screen capture of what I am seeing in the node monitor after I send the read input register command.
Untitled.cfg (16.0 KB)

ACM CONFIG.cfx (501 Bytes)

You forgot the byte count:

I fixed that (was 0) and also moved the input to the first free register. Try this and see what you get:

Untitled2.cfg (16.0 KB)

Oops My Bad.

I now have AB7072 reading the data correctly from the modbus device and I used Modbus Poll to verify that the Modbus TCP data is available from the AB7072. But I am having issues with the Ignition OPC tags reading the values. The Ignition OPC tags are showing valid with a value of zero. Just wondering if you know what the Fieldbus configurations should be set to.

Is there anyone you could direct me to to get some troubleshooting help on this part?

Thanks for all your help!!

What is this connecting to on the ethernet side? What settings are available for the Ethernet/IP connection?

Sorry for the delayed response.

I found that I was trying to read a float value. I have no idea why I thought it was a float. Changed the OPC item path to just an standard internal register and data started flowing. That’s the thing with Modbus, every set-up is different. But once you figure out how the communication is suppose to be set up, it just works.

Really appreciate the help Kyle!

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