Specified Address is Invalid message on Harmony/Magelis HMI (or Vijeo Designer HMI simulation) communicating with an EcoStruxure Control Expert / Unity Pro PLC Simulator?

Issue
Why am I getting an error: "specified address is invalid" on a Harmony/Magelis HMI (or Vijeo Designer HMI Simulation) communicating with an EcoStruxure Control Expert / Unity Pro PLC Simulator via Modbus TCP?

Environment
Configuration software on Windows PC

Product Line
Vijeo Designer, EcoStruxure Control Expert (Unity Pro v6.0+)

Cause
The simulated PLC in EcoStruxure Control Expert / Unity Pro does not support sharing the data from physical input and output addressed as Topological IO Modbus Device Addresses (%Ix.y.z, %Qx.y.z, %IWx.y.z, %QWx.y.z where x is the Rack number, y is the Slot number, and z is the Channel of the IO module) to HMI requesting reads via Modbus TCP protocol.

Resolution
To resolve the error message, perform the following actions:

1. Connect the HMI Vijeo Designer simulator to a real physical PLC.
2. Instead of using Topological Addressing, restructure your PLC application to use Unlocated Variables (IODDTs associated with the individual Channels in your IO modules). Refer to documentation for .XVM export for EcoStruxure Control Expert / Unity Pro and Symbol Linking in Vijeo Designer.