Logix EtherNET/IP

Generate a Rockwell L5X file using the 'File->Export->L5X UDT' feature. Each configuration, control, and status group in each application that has synchronized parameters will be exported as a UDT. A top level UDT will reference these group level UDTs. If there are less than 50 user defined values, the user defined values will be exported into a single UDT. Otherwise, the user defined values will be exported normally, with tags going into a their parent group.

 

Group level UDTs and the top level UDT will be prefixed with the application’s tag name prefix.

 

 

UDTs starting with 'R02_GF01_' all belong to a gas lift application that was configured with a tag name prefix of 'R02_GF01_'. The top level UDT is 'R02_GF01_GasLift_v1_1'. This UDT references the other groups. The screen grab shows this hierarchy.

 

 

When creating a tag from these imported UDTs, the tag must reference the top level UDT. If the tag does not reference the top level UDT, then the application will not be able to correctly read and write tag values at run time. You can choose whatever tag name you want when you create an instance of the top level UDT, but the name must match the configured name in the application's 'PLC Tag Name' parameter in its 'Overall Setting' group.

 

Create a controller tag from the UDT. Creating a controller scoped tag makes it available over EtherNET/IP so that the PLC Shift runtime can read and write values.

 

Write the updated configuration with new tags to the PLC.

Starting in PLC Shift version 2.3 (May 2025), the PLC Shift runtime will first try to connect to the Logix controller using a large forward open message. If this fails, the runtime will try a normal forward open. With a large forward open, the maximum packet size is set to 4002 bytes, but with a normal forward open the maximum packet size is set to 511 bytes.

 

After connecting, the PLC Shift runtime validated the tag model on the PLC. This is done one UDT at a time. Each atomic value in a UDT sends 8 bytes of information which describes its position in the model, its value type and so on. With a maximum packet size of around 400 bytes, excluding overhead, only around 50 tags can be validated. If your controller does not support larger packet sizes, care must be taken to limit the number of tags in any single to UDT to around 50 tags.