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Device types and description

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To ensure that your network communicates efficiently, PROFINET works with different device types. Conformance classes ensure seamless interaction between components.

Device types

Application relationships exist between the I/O controller, the I/O supervisor, and the I/O devices.

These involve various communication relationships for the transmission of configuration data, process data, and alarms.

The I/O controller is usually a sequential control system such as a PLC or a motion controller. During startup, the I/O controller establishes the connection to the PROFINET I/O devices and writes the startup parameters to the corresponding devices. Cyclical data exchange is then started. The PROFINET I/O controller receives all configuration information via a configuration tool. This tool reads the necessary information from the GSDML file of the device.

Field devices are referred to as PROFINET I/O devices. In the network, the I/O device is addressed using a unique device name which must be stored retentively on the device. During the startup phase, each device is also assigned an IP address by the I/O controller. This means that it can always be accessed in the network via TCP/IP. The device can be assigned to one or more I/O controllers. The I/O data is exchanged cyclically with the I/O controllers in intervals ranging from a minimum of 256 µs to a maximum of 512 ms. This is carried out separately for each data direction. In the event of an error, I/O devices send a diagnostic alarm to the I/O controller.

A PROFINET I/O supervisor is a second device in the network. It has access to all process and parameter data in parallel with the I/O controller, e.g., for diagnostic purposes. An I/O supervisor can take over a device partially (read inputs in parallel) or fully (write outputs).

Conformance classes

The PROFINET User Organization (PNO) has defined three different conformance classes (A, B, and C) for controllers, switches, and I/Os:

Standard Ethernet network components (including wireless components)
Certified PROFINET devices and controllers
Cyclic or acyclic data exchange
Basic diagnostic mechanisms

Certified PROFINET devices, controllers, and network components
Topology detection and automatic device replacement
Extended diagnostics

Certified devices and network components with hardware support
Highly deterministic data transmission
Maximum performance and synchronism

Device description

In order to be able to integrate components into an automation solution, various information regarding the device must be provided in the engineering steps.

Communicate device parameters quickly and clearly, thanks to the GSD file

In the PROFINET IO system, the device description is imported into the relevant engineering system as a GSD (General Station Description) file in XML format.

The file describes hardware communication and device parameters that are set in the configuration software. In addition, they are transferred to the controller and sent to the device when a connection is established.

In addition to a description of the device and the communication properties, the GSD file also contains all component error messages in text format.

A PROFINET IO diagnostics tool only needs the name of the manufacturer and the device ID in order to output error messages in plain text.