Modbus Configuration on the Emerson ROC800
Key Takeaway
How to configure Modbus RTU and TCP on the ROC800 — slave for SCADA access, master for instrument polling, register mapping, and byte order.
Quick Answer
The ROC800 supports Modbus RTU slave (serial RS-485), Modbus TCP server (Ethernet port 5000), and Modbus RTU master (polling field instruments). ROC register addresses for flow data are documented in Emerson's register reference. Ignition and Geo SCADA can poll ROC via Modbus TCP.
How Do You Configure Modbus?
- Navigate to Communications → Modbus in ROCLINK 800
- For slave: set slave address (1-247) and serial port or enable TCP
- For master: configure target device address, register range, poll rate
- Configure byte order to match SCADA driver expectations
What Registers Hold Flow Data?
Register addresses are documented in Emerson's ROC800 Register Reference Manual. Addresses vary by firmware version. ROCLINK 800 displays the register address for each configured value. See Modbus register types and function codes for protocol details.
Frequently Asked Questions
Port 5000 for Modbus TCP by default. Separate from ROC protocol (port 4000) and DNP3 (port 20000).
Yes. Ignition's Modbus TCP driver polls ROC800 holding registers for flow rates, pressures, temperatures, and volumes.
Documented in Emerson's Register Reference Manual by model and firmware version. ROCLINK 800 displays register addresses for each configured value.