Modbus RTU Flexy 205

I am wanting to read a variety of registers over modbus RTU to a ABB VFD. I have a few questions/concerns. There is a potential of 100+ drives I am wanting to read, so I hoping I can use just topic A and assign the individual Modbus ID for the parameter I am wanting to read. For example I assigned a tag to 40101,1. Individually it works fine. However… If I add another tag and its not consecutive i.e 40103,1, I get a red flag and the error is “unknown” (see image 2). But, if the tag was assigned 40102,1 no errors and works fine (see image 1).

A) Is there a reason why the tags have to be consecutive? Perhaps I am doing something wrong?
B) Any concern reading 100+ modbus RTU drives with 5-6 tags each?


Most lilkely the issis that there is no variable at that address you are trying to reach. I would also select “Disable Tags in Error” under the general Settings in IO Servers. Can you provide a backup with support file? This can be done using ebuddy. I would need to review the event logs to determine what is occuring.

Thanks for the reply. I know the variable I am reaching is good, because it would work as long as I didn’t have any other tags. However… I am seeing something interesting:

I selected “Disable Tags in Error” and it goes in and out of error. I can see every second or so it will update the value, then error all tags out.

As requested before, can you get a backup with support files? I would like to review the event logs for errors.

Here is error list and backup file.

ewon.tar (343 KB)


Are you using a adressing offset? I see several Modbus Illegal data addresses in the event logs.

Can you alter the addresses by +/- 1? We usually see registers start at evens such as 40000, 40002, 40008.

The way the drive addresses it’s modbus is:

For example to look at menu 1.01 and in this case is motor speed

You would take 40000 + 101 = 40101

I can individually look at them it works fine

But if you add multiple tags, they will all error out every second or so (based on my polling rate).

Furthermore, if I were to add two modbus registers consecutively… they work fine:


I will investigate this issue a little further, and escalate if need be.


Any additional thoughts on this?


I will check for an update on this issue. In the mean time, can you try connecting with a modbus simulator and see if the same issue occurs with that flexy? I tried on my end to replicate this issue, but i have not had success.

I wish to eliminate the possibility that the Flexy is defective.

Would you be available for a virtual meet around 11am central time today? I discovered something and it would be easier to show than explain.


I sent you my email for the meeting invite.

Sounds good. Finishing up at a customer and I’ll send you and invite for 11am central time today.