Efficient Networks S120 manual RT classes for Profinet IO Description, IRTflex, IRTtop

Models: S120

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Communication PROFIBUS DP/PROFINET IO 10.3 Communications via PROFINET IO

10.3.3RT classes

10.3.3.1RT classes for PROFINET IO

Description

PROFINET IO is a scalable realtime communications system based on Ethernet technology. The scalable approach is expressed with three realtime classes.

RT

The RT communication is based on standard Ethernet. The data is transferred via prioritized Ethernet message frames.

IRTflex

This realtime class is not supported in FW 2.5 SP1.

IRTtop

In addition to the bandwidth reservation, the message frame traffic can be further optimized by configuring the topology. This enhances the performance during data exchange and the deterministic behavior. The IRT time interval can thus be further optimized or minimized compared with IRTflex.

In addition to the isochronous data transfer, with IRT even the application (position control cycle, IPO cycle) can be synchronized in the devices. This is an essential requirement for closed-loop axis control and synchronization via the bus.

Table 10-33 Comparison between RT and IRTtop

RT class

RT

IRTtop

Transfer mode

Switching based on the MAC address;

Path-based switching using a topology-

 

prioritization of the RT message frame

based planning; no transmission of

 

possible using Ethernet-Prio (VLAN

TCP/IP frames in the IRTtop interval.

 

tag)

 

MinDeviceInterval

Typically 2-8 msec

Fully deterministic, also for 250 µsec

Isochronous application

-

Yes

Start time of the isochronous

-

Times for receiving the data scheduled

application

 

exactly. A synchronous application can

 

 

be started directly afterwards (similar to

 

 

DP)

Determinism

Variance of the transmission duration

Exactly planned transfer; times for

 

by started TCP/IP message frames

transmission and receiving are

 

 

guaranteed for any topologies.

Reload the network configuration after

-

Whenever the topology or the

a change

 

communication relationships

 

 

change

Cross-traffic (controller-controller)

-

Yes

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Drive Functions

Function Manual, (FH1), 07/2007 Edition, 6SL3097-2AB00-0BP4

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Efficient Networks S120 manual RT classes for Profinet IO Description, IRTflex, RT class IRTtop