Roadmap › Industrial Automation — PLC, SCADA, Modbus and OPC UA › Module: Supervisory Systems and Communication
Lessons in this course (10)
7. Industrial networks and Modbus
Intermediate★ Must knowLesson 7 of 10
| Network | Type | Common with |
|---|---|---|
| Modbus RTU | Serial (RS-485), master/slave | Meters, drives, simple devices |
| Modbus TCP | Ethernet, client/server, port 502 | Everywhere — simplest Ethernet protocol |
| PROFIBUS DP | Fieldbus (RS-485) | Siemens installations |
| PROFINET | Industrial Ethernet, real-time | Siemens |
| EtherNet/IP (CIP) | Industrial Ethernet | Rockwell / Allen-Bradley |
| EtherCAT | Very fast Ethernet fieldbus | Motion control, Beckhoff |
| CAN / CANopen, DeviceNet | Fieldbus | Machines, vehicles |
| IO-Link | Point-to-point smart sensor link | Sensor diagnostics and parameters |
| HART | Digital signal over 4–20 mA | Process instruments |
Modbus data model:
| Table | Access | Function codes |
|---|---|---|
| Coils (0xxxx) — 1 bit | Read/write | FC01 read, FC05 write single, FC15 write multiple |
| Discrete inputs (1xxxx) — 1 bit | Read-only | FC02 |
| Input registers (3xxxx) — 16 bit | Read-only | FC04 |
| Holding registers (4xxxx) — 16 bit | Read/write | FC03 read, FC06 write single, FC16 write multiple |
32-bit floats use two registers — check the word/byte order (big-endian vs "word swapped") in the device manual. Modbus has no authentication or encryption — keep it on isolated networks.