What is PROFINET
PROFINET IO in practice: controller, device and supervisor, GSDML files, RT and IRT communication, conformance classes and how it differs from PROFIBUS.
Roles
| Role | What it is | Example |
|---|---|---|
| IO controller | Usually the PLC; owns the cyclic data exchange | S7-1500 CPU, CODESYS controller |
| IO device | Field device or remote I/O station | ET 200SP, drive, valve terminal |
| IO supervisor | Engineering / diagnostic tool, temporary | TIA Portal, PRONETA |
One device can be both: an I-device is a PLC that acts as an IO device for a higher-level controller.
Configuration
Every device type is described by a GSDML file (XML: modules, submodules, parameters, diagnostics, supported features). The controller's project lists devices by device name (NameOfStation), not by IP address. At startup the controller finds each device by name via the DCP protocol, assigns the configured IP address and starts cyclic exchange — see device names.
Communication classes
- TCP/UDP-IP — non-real-time: configuration, acyclic records, web servers, OPC UA run in parallel on the same cable.
- RT (Real-Time) — cyclic IO data directly in Ethernet frames (EtherType 0x8892, no IP stack), update times in the millisecond range, standard switches.
- IRT (Isochronous Real-Time) — reserved time slots and hardware support in devices and switches for motion control; cycle times down to 31.25 µs in recent specification versions.
Conformance classes
| Class | Adds |
|---|---|
| CC-A | Basic RT, alarms, diagnostics |
| CC-B | Network diagnostics via SNMP, topology (LLDP); system redundancy option CC-B(PA) |
| CC-C | IRT — isochronous operation, hardware support required |
| CC-D | PROFINET over TSN |
PROFINET vs PROFIBUS
| PROFIBUS DP | PROFINET IO | |
|---|---|---|
| Physical layer | RS-485, max 12 Mbit/s | Ethernet 100 Mbit/s full duplex (and more) |
| Addressing | Station address 0…126 | Device name + IP address |
| Device description | GSD (text) | GSDML (XML) |
| Topology | Line with repeaters | Line, star, tree, ring (MRP) |
| Other traffic on the same cable | No | Yes (IT protocols in parallel) |
Typical issues are device names, duplicate IP addresses and topology errors — see PROFINET diagnostics.
Connections
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Sources
- PROFINET — technology overview — PROFIBUS & PROFINET International (PI)
- PROFINET Technology — The Easy Way to PROFINET (2024) — PROFIBUS & PROFINET International (PI)
- PROFINET System Description, System Manual 03/2012 — Siemens AG
- PROFINET with STEP 7 — Function Manual 11/2022 — Siemens AG
Updated 2026-10-02