I’m trying to setup a couple of tags in an AB Micro850 PLC referencing this thread . However I’m lost on the setup. I’ve never used Modbus before. Below is a snapshot of the plc program, I want to start off with a tag to show if the machine is on or off which I think reading set coil _B001 is what…

[image] I just found this in the PLC software, not sure whether this is needed to map the addresses?

Yes, you have to map each variable you want to access via Modbus.

I’ll give it a shot after machine shut down

I was able to map the variables and upload it to the PLC. It worked well, I thought this was going to be more complicated but was actually pretty simple. thanks

I am able to connect to a Micro850 using the Modbus TCP protocol but I can’t get values from it. I have the Modbus Mapping setup in the PLC as shown here: [image] I have tried many different names in the OPC Item Path. Note: The tag names in pic below match the name used in the OPC Item Path, so …

Did you enable ModbusTCP in CCW? (As per the little warning top right of your first image)

[image] james.wilson: I don’t know how to determine if this problem is on the PLC side or Ignition side. Can anyone suggest how to determine Use ModPoll or similar software to rule out Ignition as a start

Yes, Modbus TCP was enabled or Ignition wouldn’t be able to connect to it. ModPoll was helpful. I found that having a single invalid tag pointing to a Modbus address in Ignition was causing my good tags from getting data from other Modbus addresses. Once I disabled all my tags where I was using tria…

[image] james.wilson: I found that having a single invalid tag pointing to a Modbus address in Ignition was causing my good tags from getting data from other Modbus addresses. I encountered an issue similar to this today. I was able to access some Modbus registers in the Micro850, but when I…

Modbus Addressing AB Micro850

Ignition

pturmel September 15, 2023, 5:15pm 15

FWIW, if you do much with this family of processors, you might want to look at my latest EtherNet/IP driver. (So you don't have to set up Modbus in the ML8xx.)