I/O auto-assignment with OPC clients

Using I/O auto-assignment with the OPC communication protocol may require that you add overrides to allow communication between the IDE and certain PLCs, such as Allen-Bradley Logix and Siemens S7 controllers.

If you are using auto assignment to communicate with a device connected to an OPC Server on a different node (for example, a Communication Driver on a remote Galaxy), you will use overrides to build valid I/O references with all required parameters to fulfill the OPC hierarchical path. If bulk edits are required, you can copy and paste between the Mapping view and Microsoft Excel.

I/O auto assignment uses the syntax: <DI Object.ScanGroup>. <Object.Attribute>. It is the first part of the syntax that limits how the OPCClient builds the I/O auto assignment reference, since additional parameters in the device hierarchy, such as Ethernet ports and backplanes are not included. While these parameters may be logically viewed as part of the DI Object.ScanGroup reference, you must add the parameters to the Object.Attribute override column (not the DI Object.ScanGroup override column) to create the fully qualified I/O reference.

Using DDESuiteLink instead of OPC will accommodate the automatically generated I/O reference to these PLCs, and in most cases, overrides will not be needed.

Caution: Do not change the order of references, either in Excel or in the Mapping view by sorting, grouping, or filtering the reference list while editing references.