Yokagawa GX20 Modbus TCP

Hi all, Im try to set up a Yokagawa GX20 chart recorder to read and write to ignition through modbus TCP. I have no experience with modbus or these chart recorders. I can get ignition to connect to the chart recorders but I can not get any tags to link up. Actually I did but somewhere I changed a setting in either the chart recorder or ignition and now all I get is a a ? mark on the tags.These chart recorders can be setup as either the client/master or server/slave. I am a little confused on the whole client/server master/slave setup but what I understand is that ignition is the client and the chart recorder is the server. Am I correct? I downloaded a modbus scanner onto the ignition server and it pulled all values in that I am looking for so I know i can reach the recorder. Any help is much appreciated.


Now that you know what addresses are valid you just need to make some tags in Ignition.

The address syntax to use in the OPC Item Path is explained here in the user manual.

I have made some tags but they are not connecting. There are 5 int32 tags and i am looking at gathering 300001 through 300010. I have tried addressing them in ignition a couple of different ways start 1 end 10, step is checked, input register(int32), address 1and a couple of different combinations but when i bring the tags in they are dispaying null values but when i run the modbus scanner they do have actual values in them. tags are green with ?marks on them.

any more Ideas? Im assuming its on the chart recorder side of things but not sure what to look for.
thanks again!!

Try toggling the one-based addressing setting in the driver.

If that doesn’t work, instead of using the mapping, try creating just one tag manually with an address like [device-name]IRI1. Maybe use Wireshark to capture the traffic from Ignition vs the traffic from the scanner.

Another thing to check is to verify if the High/Low word setting is correct as well. Modbus itself does not define 32-bit data types, but rather 16-bit only. For 32-bit data types, each vendor can implement the High/Low word order and is not consistent.

Hi guys thanks for your ideas. One quick question. Is ignition a client or is it a server in the modbus world? Thanks

It’s a client aka master.

Hi Kevin, I tried the couple of things you asked. When in wireshark I do not see any modbus requests unless I run the modbus scanner then I see a query from the server ip address and a response from the chart recorder. I was pretty sure that Ignition was client so shouldn’t I see it querying?
I really appreciate your help.

Might be time to call in and let support take a look.

Great minds think alike I just called them and are waiting for their call back.

Thanks again!!

Hi winslow , excuse me, Would you have a Modbus TCP mapping register about the GX20?