Irt - Siemens SIMATIC ET 200AL System Manual

Distributed i/o system

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5.5 Real-time communication

In the Cut through process the entire data package is not stored temporarily in a buffer, it is

passed directly onto the target port as soon as the target address and the target port have

been determined.

The times required by the data package to pass through the switch are then minimal and

independent of the frame length. The data are only stored temporarily in accordance with the

Store and forward process as per priority when the section between the target segment and

the port of the next switch is occupied.

IRT

Isochronous real-time communication (IRT)

IRT is a synchronized communication protocol for cyclic exchange of IRT data between

PROFINET devices. A reserved bandwidth is available in the send cycle for IRT data. The

reserved bandwidth ensures that the IRT data can be transferred at reserved synchronized

intervals, without being influenced also by higher other network loads (such as TCP/IP

communication, or additional real-time communication).

PROFINET with IRT is synchronized communication in reserved time intervals. With IRT you

have the option to be able to control time-critical applications such as motion control via

PROFINET. With IRT you use further advantages:

• High-precision deterministics allow highest control quality and thus, for example, exact

positioning of axes

• Simple and flexible integration of PROFINET devices for real-time applications in existing

company networks

• Shortest response times and highest deterministics by means of bandwidth reservation

and thus also for applications that have to satisfy highest performance requirements

(e.g., printing control/position control for presses, print-mark recognition with packaging

• Secured standard communication parallel to real-time communication via the same

transmission medium

• You can continue to use standard components for your PROFINET IO system outside of the

PROFINET with STEP 7

Function Manual, 05/2021, A5E03444486-AL

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