Real-Time (Rt) And Isochronous Real-Time (Irt) Communication - Siemens SINAMICS Series Operating Instructions Manual

Descriptions of functions
10.5 Communication via PROFINET IO
Note
PROFINET for drive technology is standardized and described in the following document:
• PROFIBUS profile PROFIdrive – Profile Drive Technology
Version V4.1, May 2006
PROFIBUS User Organization e. V.
Haid-und-Neu-Straße 7, D-76131 Karlsruhe, Germany
http://www.profibus.com, Order Number 3.172, spec. Chapter 6
• IEC 61800-7
Note
For a CUD with inserted CBE20, the cyclic PZD channel is deactivated for PROFIBUS DP.
By setting parameter p8839 = 1, the PZD channel can be reactivated, see Chapter "Parallel
operation of communication interfaces (Page 438)".
10.5.2.1

Real-time (RT) and isochronous real-time (IRT) communication

Real-time communication
When communication takes place via TCP/IP, the resultant transmission times may be too
long and non-deterministic to meet production automation requirements. When communicat-
ing time-critical IO user data, PROFINET IO therefore uses its own real-time channel, rather
than TCP/IP.
Real time means that a system processes external events over a defined period.
Determinism
Determinism means that a system will react in a predictable ("deterministic") manner.
With PROFINET IO with IRT, it is possible to precisely determine (predict) transmission
times.
PROFINET IO with RT (Real Time)
Real-time data is treated with a higher priority than TCP(UDP)/IP data. Transmission of time-
critical data takes place at guaranteed time intervals. RT communication is the basis for data
exchange with PROFINET IO.
PROFINET IO with IRT (Isochronous Real Time)
Isochronous real time: Real time property of PROFINET IO where IRT telegrams are
transferred deterministically via planned communication paths in a defined sequence to
achieve the best possible synchronism and performance between the IO controller and IO
device (drive unit). IRT is also known as time-scheduled communication whereby knowledge
about the network structure (topology) is utilized. IRT requires special network components
that support planned data transfer.
492
SINAMICS DCM DC Converter
Operating Instructions, 12/2018, A5E34763375A