Modicon Modbus addressing

I’m working with a PLC programmer who is using a Modicon M241. I’ve never used the Modbus driver.
I have connected to it with the Modbus TCP driver, but all I’m having trouble getting to the correct addresses.

The addresses that I have been given by the programmer are %MW60200, %MW62200… and more addresses with this format. I’ve found some documentation that give me the some Modbus equivalents to %MW addresses, but not ones with this high of number.

Does anyone know how I can translate these to Modbus addresses? Or where I can tell the PLC programmer to look for them?

Thank you.

So are you saying that doing [Your Device Name]HR60200 on the item path of your Ignition tag is not working? This should be a standard address in Modbus.

No… I’m saying that I don’t know if HR60200 = %MW60200.

I’ll have the programmer put some data in there and see if it’s working.

Thank you for the reply.

Oh I see. If you look under the advanced tab in your device setup, there is a checkbox that says “One Based Addressing”. If you don’t seem to see the correct data, try changing that option. I have found that sometimes addresses are skewed by one in Modbus and changing this paramater will fix that skew.


Great. I’m seeing most of the correct data, the addresses are skewed by one though.
Thanks a lot!

One that has incorrect data in it is a string that is address %MW60200.
If I set the ignition tag to HR60200 (or HR60201 to adjust for skew), is that only looking at a single 16 bit word?
If it is, how do I address it in ignition to read all of the string data?

Have a look at the string setup info, about halfway down on this page: