Learning outcomes
- Explain the key principles of modbus tcp configuration.
- Carry out a structured practical check or configuration task.
- Recognise common faults, risks and evidence needed for diagnosis.
Module 10 · Lesson 3
Modbus TCP configuration
Configure Modbus TCP clients and servers using IP addressing, unit identifiers and port 502.
Before you begin
PLC/SCADA simulator and Modbus TCP server.
Safety: Use site procedures, approved test equipment and competent supervision. Never bypass a protection or interlock without formal control.
Step-by-step learning
- Confirm IP connectivity and that TCP port 502 is reachable.
- Create a device connection with timeout and retry settings.
- Map registers with correct data type, byte order and scaling.
- Test behaviour when the server is unavailable or returns an exception.
Ian's practical tips:
- A successful TCP connection does not prove the register map is correct.
- Limit polling rate to what the device and network can reliably support.
Fault-finding questions
- What should be happening, and what evidence proves it?
- Where is the last known correct signal, voltage, state or process condition?
- What changed immediately before the fault?
- Can the system be divided into smaller testable sections?
Practical activity
Create a one-page test record for this lesson. Include expected values, measured results, equipment used, risks controlled, defects found and the final proven condition.