Distributed I/O connects sensors and actuators around a machine to the CPU. In this example, ET 200 stations exchange that data over an Ethernet network running PROFINET. One IO-controller (the CPU) exchanges cyclic data with several IO-devices. The animation shows output data travelling toward the devices and input data returning to the controller. Disconnect a station to see the exchange stop.
The CPU on the left is the IO-controller. The three ET 200 stations are IO-devices. The controller supplies output data and each device supplies input data at its configured update interval. The animation shows these directions as packets moving along the network. Select ✂ Pull station 2 to interrupt that station's connection and inspect the resulting diagnostic indication.
With RT, the simulation varies packet timing to illustrate traffic sharing the network. Select IRT to see the scheduled phase hold the illustrated packets at a consistent position in each cycle. After you disconnect a station, the diagnostic indication identifies the affected device so you can start investigating its connection.
A PROFINET controller identifies its configured device through the device name, as well as using an IP address for communication. Load the device description, its GSDML file, when required; place the device in the network view and assign the configured name to the physical station. At startup, the controller can identify it by that name and assign the configured IP. A mismatched name can leave the station unreachable even when its wiring and power are correct.
🎛️ IO-controller is usually the CPU. It holds the device configuration, exchanges cyclic output and input data with the devices, and provides diagnostics for those connections.
📟 IO-device can be an ET 200 station, drive or valve island. Its capabilities are described by a GSDML file. The device name identifies the station, and its configured I/O data is exchanged cyclically.
⏱️ RT (Real-Time) carries cyclic data on shared Ethernet. Update times of a few ms suit many machine applications; choose the configured timing according to the actual control requirements.
🎯 IRT (Isochronous) uses a reserved, scheduled communication phase for synchronized operation. It supports applications such as coordinated motion where the timing relationship between devices must be controlled.
A new ET 200 station has power and network wiring, but the CPU reports it as "not reachable." Its IP looks correct. Which device setting should you check next?