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Introduction
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A PROFINET IO system consists of the following devices:
•
The IO Controller, which contains the automation program and
controls the automation task.
The IO Device, which is a field device such as an encoder, mon-
itored and controlled by an IO Controller.
The IO Supervisor is software typically based on a PC for set-
ting parameters and diagnosing individual IO Devices.
An application relation (AR) is established between an IO Control-
ler and an IO Device. These ARs are used to define communica-
tion relations (CR) with different characteristics for the transfer of
parameters, cyclic exchange of data and handling of alarms.
The characteristics of an IO Device are described by the device
manufacturer in a General Station Description (GSD) file. The lan-
guage used for this purpose is the GSDML (GSD Markup Lan-
guage) - an XML based language. The GSD file provides the su-
pervision software with a basis for planning the configuration of a
Within PROFINET IO, process data and alarms are always trans-
mitted in real time (RT). Real time in PROFINET is based on the
definition of IEEE and IEC, which allow for only a limited time for
execution of real-time services within a bus cycle. The RT com-
munication represents the basis for the data exchange for
PROFINET IO and real-time data are always treated with a higher
priority than TCP (UDP)/IP data.