Allen-Bradley / Rockwell — EtherNet/IP
EtherNet/IP (CIP, Common Industrial Protocol) is the communication protocol used by Allen-Bradley / Rockwell ControlLogix / CompactLogix series PLCs.
The EIP driver in this gateway currently reads CIP attributes (class / instance / attribute) only. Symbolic tags common on ControlLogix (e.g. MyController:Pump1.RPM) require a separate "Read Tag Service", which is planned for a future release. Until then, if you need symbolic tags, we recommend bringing them in over OPC-UA through a gateway such as Kepware.
Registration Form Fields
| Field | What to enter | Example |
|---|---|---|
| IP address | IP of the PLC | 192.168.0.90 |
| Port | EtherNet/IP port | 44818 (standard) |
| Backplane (backplane) | Backplane number | 1 |
| Slot (local-slot) | CPU slot number | 0 |
On the PLC side, the EtherNet/IP module must be enabled in RSLogix / Studio5000.
PLC Address Notation for Tags
Enter the EIP CIP coordinates in the <class>,<instance>,<attribute> format. Both decimal and hexadecimal beginning with 0x are accepted.
| Notation | Meaning |
|---|---|
0x01,1,1 | Identity Object → Vendor ID |
0x01,1,2 | Identity Object → Device Type |
0x01,1,7 | Identity Object → Product Name (string) |
0x6B,1,1 | Symbol Class instance 1 attribute 1 |
0x6C,1,1 | Template Class |
How to Find the CIP Coordinates
- Check the attribute information in the Tag Browser in Studio5000
- Capture existing EIP traffic with Wireshark or a similar tool
- Use the mapping table from the manufacturer / integration partner
If symbolic tags are more familiar to you, the Kepware route mentioned above is far simpler.
Data Type Matching
| PLC value | Data type | Type modifier |
|---|---|---|
| String (product name, status, etc.) | String | (leave empty) |
| Integer (Vendor ID, DeviceType, etc.) | Integer | (leave empty) |
| Float | Float | (leave empty) |
| Boolean | Boolean | (leave empty) |
The EIP driver takes the raw response bytes as a string and then casts them in post-processing according to [Data type]. If you need to convert large integers or floats, post-process the value with Apply Formula.
Common Problems and Fixes
| Symptom / message | Possible cause | Fix |
|---|---|---|
| "Connection timeout" | Port 44818 blocked, EtherNet/IP module disabled | Enable the EtherNet/IP module in RSLogix / Studio5000 |
| "Forward Open failure" | rack/slot or backplane mismatch | Correct backplane / slot using the table above |
| "Class/Instance not found" | Incorrect CIP coordinates | Verify the coordinates with the Studio5000 Tag Browser or Wireshark |
| Value appears garbled | Raw bytes are taken as a String as-is | Interpret as little-endian with a formula, or use the Kepware route |
More Examples / Automated Registration
See the EIP examples in Advanced — REST API.