Configuring a Siemens PROFINET device means four things: add it to the project and assign it to the IO controller, give it a device name and an IP address, set the update time, and optionally interconnect the ports in the Topology view. Download the hardware configuration, then write the device name to the real device with Online & diagnostics → Assign PROFINET device name. The controller finds the device by that name and gives it the IP address from the project at every start-up.
- The device name is what identifies a device — lowercase letters, digits, hyphens and dots only.
- The IP address normally comes from the project, not from the device.
- Watchdog = update time × accepted cycles (default 3), so a shorter update time also means a quicker failure report.
- Configure the topology if you want device replacement without a memory card, precise diagnostics or IRT.
MAC Address, Device Name and IP Address
Every PROFINET device carries three identities, and confusing them causes most commissioning problems. The MAC address is fixed in the hardware. The device name is written once into the device. The IP address is handed out by the IO controller each time the system starts.
The Configuration Workflow
The same nine steps apply to remote I/O, drives, HMI panels and third-party devices. Steps 1 to 6 are offline in TIA Portal, step 7 is the download, and steps 8 and 9 happen on the real hardware.
Device Name Rules
PROFINET names follow DNS conventions, which is stricter than most people expect. TIA Portal will reject an invalid name, but a name that is valid and simply different from the one in the device also stops communication — so keep a naming standard, for example <device type>-<area>.
| Rule | Allowed | Not allowed |
|---|---|---|
| Characters | Lowercase letters a–z, digits 0–9, hyphen and dot | Uppercase letters, spaces, underscore, special characters |
| Start and end | Must start and end with a letter or digit | A name starting or ending with a hyphen or dot |
| Length | Up to 240 characters in total, each label up to 63 | Longer names |
| Reserved forms | Descriptive names such as et200sp-line1 | A name in the form n.n.n.n, or starting with port-xxx |
| Uniqueness | One name per device on the network | The same name on two devices — both will fail |
IP Addressing and an Address Plan
In a machine network the project holds the IP addresses and the controller assigns them. Other options exist for special cases.
| Method | Who sets the IP | When to use |
|---|---|---|
| Set in the project (default) | The IO controller assigns it at start-up from the configuration | Almost all machines — the device needs only its name |
| Set directly at the device | Keypad, display or Online & diagnostics | Devices that must keep their own address, or commissioning tests |
| Obtain from a DHCP server | A DHCP server on the network | Rare in machine automation; plant IT networks |
| Via a user program | The program uses the relevant instruction to assign the address | Machines delivered with a variable address plan |
A simple address plan keeps a plant maintainable. Reserve ranges by device type so that any engineer can guess where a station sits.
| Station | Device name | IP address | Subnet mask |
|---|---|---|---|
| CPU | plc-line1 | 192.168.0.1 | 255.255.255.0 |
| HMI panel | hmi-line1 | 192.168.0.5 | 255.255.255.0 |
| Remote I/O | et200sp-line1 | 192.168.0.11 | 255.255.255.0 |
| Drive | g120-conv1 | 192.168.0.21 | 255.255.255.0 |
| Switch (managed) | switch-line1 | 192.168.0.30 | 255.255.255.0 |
Commission PROFINET devices on real hardware
Assign names, set update times, build a topology and replace a device live in the lab. Pune classroom or live online.
Update Time and Watchdog
The send clock is the time grid of the whole PROFINET line. Each device exchanges its data every send clock or every n-th send clock — that is the update time. If data is missing for the configured number of cycles, the controller reports a station failure.
| Setting | What it does | Typical value |
|---|---|---|
| Send clock | The basic time grid of the PROFINET line | 1 ms (250 µs to 4 ms) |
| Update time | How often this device exchanges data — a multiple of the send clock | 1 – 4 ms; auto-calculate is usually right |
| Accepted update cycles without IO data | How many missed cycles before the device is reported failed | 3 |
| Watchdog time | Update time × accepted cycles | 3 ms at 1 ms update time |
| Prioritised start-up | Shortens the start-up of a device after power-on | Only for tool changers and similar fast restarts |
Ports, Topology and MRP
Most PROFINET devices have two ports and an internal switch, so devices can be wired in a line without extra hardware. Drawing that wiring in the Topology view is optional for basic operation, but it unlocks several features.
| What topology gives you | Needs |
|---|---|
| TIA compares planned and actual wiring and shows the difference | Ports interconnected in the Topology view |
| Device replacement without a programming device or memory card | Topology + the option enabled on the CPU + a device in factory state |
| Clear diagnostics: which cable, which port | LLDP-capable devices (all standard PROFINET devices) |
| Media redundancy (MRP) ring | Ring wiring, one MRP manager, the rest as clients |
| IRT for synchronised motion | Topology is mandatory, plus IRT-capable devices and switches |
Modules and I/Q Addresses
Once the device is in the project, its modules appear in the Device overview and TIA Portal assigns input and output addresses. These are the addresses your program uses.
For a SINAMICS drive the module is a telegram, and the addresses are the control and status words — see G120 Telegram Selection in TIA Portal.
Device Replacement Without a Memory Card
This is the feature that makes PROFINET maintenance simple: a failed device is replaced by an identical one in factory state, and the controller names and addresses it automatically.
It only works when all three conditions are met: the topology is configured, the option is enabled on the CPU's PROFINET interface, and the new device is in factory state with the same article number and a compatible firmware version.
Common Faults and Fixes
Almost every PROFINET commissioning fault comes back to a name, an address, a port or a module mismatch. Capturing the traffic with Wireshark quickly shows whether a device is answering at all.
| Symptom | Likely cause | Fix |
|---|---|---|
| BF LED flashing on the device, PLC reports it missing | Device name not assigned, or spelled differently from the project | Online & diagnostics → Assign name, exactly as in the project |
| Device comes up, then drops out at random | Update time too short, damaged cable, unmanaged switch under load | Increase the update time, check the cable, use an industrial switch |
| "Configured and actual topology differ" | Cable in the wrong port, or ports not interconnected in the project | Correct the wiring, or update the Topology view |
| New device after replacement does not start | It is not in factory state, or topology / the replacement option is missing | Reset to factory settings, configure the topology, tick the option on the CPU |
| Device not found when assigning a name | PG on a different subnet, or the device is behind a router | Put the PG in the same subnet; DCP does not pass through routers |
| Module reports "not present" in the Device overview | Configured module differs from the one plugged in | Match the article number and firmware in the project |
Checklist Before Download
| Before download | Check |
|---|---|
| Device name | Lowercase, unique, identical in the project and on the device |
| IP address | In the same subnet as the CPU, no duplicates |
| Article number and firmware | Match the real device, otherwise modules go "not present" |
| Update time | Auto-calculated or deliberately chosen, watchdog acceptable |
| Topology | Ports interconnected if you want replacement or IRT |
| I/Q addresses | Noted from the Device overview for the PLC program |
Step-by-Step Lab: Configure a Device End to End
Hands-on- An S7-1200 or S7-1500 and one PROFINET device (remote I/O or a drive), plus a PC with TIA Portal on the same network.
- The device in factory state, or its current name noted.
- Estimated time: 45 minutes.
Add the device and assign it to the controller
Take the device from the hardware catalog (install its GSDML first if it is not there) and drag it onto the PROFINET line of the CPU in the Network view.
Set the name and IP address
Rename the device following the naming rules and set an IP address in the CPU's subnet.
Set the real-time settings
Open the real-time settings and note the send clock, the update time and the accepted update cycles.
Interconnect the ports
In the Topology view, drag from the CPU port to the device port exactly as the cable runs.
Download and assign the name online
Compile, download the hardware configuration, then use Online & diagnostics → Assign PROFINET device name.
Force a fault and read the diagnostics
Swap the cable into the other port of the device and go online.
You can configure a device if you can explain why the device needed a name but no IP address entered on it, what the watchdog time works out to, and what the topology gives you beyond a pretty picture.
Once the device is configured, the program takes over — see Siemens PLC and VFD networking for the ways a PLC exchanges data with a drive.
Frequently asked questions
How do I assign a PROFINET device name in TIA Portal?
Set the name in the device properties, then go online and use Online & diagnostics → Functions → Assign PROFINET device name. Select the device in the list, check that the MAC address is the right one, and write the name. The controller then gives the device its IP address at start-up.
What are the rules for a PROFINET device name?
Only lowercase letters, digits, hyphens and dots. The name must start and end with a letter or digit, must not look like an IP address, and must not begin with port-xxx. Each label may be up to 63 characters and the whole name up to 240. Every device on the network needs a unique name.
Does every PROFINET device need an IP address set on it?
No. In the normal case the project holds the IP address and the IO controller assigns it at start-up once it has found the device by name. You only set an address on the device itself for special cases or for commissioning tests.
What is the update time and what should I set?
The update time is how often the controller and the device exchange their cyclic data — always a multiple of the send clock. The automatic calculation is right for most applications; a shorter time means fresher data but also a shorter watchdog before a station failure is reported.
Why does TIA Portal report that the configured and actual topology differ?
Because a cable is in a different port from the one drawn in the Topology view. Either correct the wiring or update the topology. This message only appears if you interconnected the ports in the project, which is also what makes the diagnostics so precise.
How does device replacement without an exchangeable medium work?
The controller uses the configured topology and the neighbour information reported by LLDP to recognise which device is plugged into which port. It then writes the name and IP address to the new device automatically. The new device must be in factory state and the option must be enabled on the CPU's PROFINET interface.
Why can't I see the device when I search for accessible nodes?
Usually the programming device is on another subnet, or the connection passes through a router. Name assignment uses DCP, which works only within the same subnet. Connect the PG to the same network as the device and search again.