Siemens SIMATIC ET 200SP Manual page 13

Isochronous real-time communication
Synchronized transmission method for cyclic exchange of IRT data between PROFINET
devices. A reserved bandwidth is available within the send clock for IRT data. The reserved
bandwidth ensures that the IRT data can also be transferred without being affected by
another high network load (e.g. TCP/IP communication or additional real time
communication) at reserved, chronologically synchronized intervals.
A topological configuration is required for IRT.
Note
IO controller as sync master with IRT communication
We recommend also operating the IO controller as a sync master when configuring the IRT
communication.
Otherwise, IO devices with IRT and RT configuration could fail as a result of sync master
failure.
You can find more information on the configuration of synchronized PROFINET devices in
sync domains in the STEP 7 online help and
● As of STEP 7 V12, in the PROFINET with STEP 7 V13 function manual
● As of STEP 7 V5.5, in the system manual PROFINET System Description
(http://support.automation.siemens.com/WW/view/en/19292127)
Prioritized startup
Prioritized startup describes the PROFINET IO functionality for accelerating the startup of IO
devices in a PROFINET IO system with IRT and RT communication.
The function reduces the time that the appropriately configured IO devices require in order to
return to cyclic user data exchange in the following cases:
● After the supply voltage has returned
● After a station has returned
● After IO devices have been activated
Note
Dependency of the startup time
The startup time depends on the number and type of modules.
You can find more information on this topic in the STEP 7 online help and
● As of STEP 7 V12, in the function manual PROFINET with STEP 7 V13
(http://support.automation.siemens.com/WW/view/en/49948856)
● As of STEP 7 V5.5, in the system manual PROFINET System Description
(http://support.automation.siemens.com/WW/view/en/19292127)
IM 155-6 PN ST interface module (6ES7155-6AU00-0BN0)
Manual, 12/2014, A5E03576904-AC
Product overview
2.2 Functions
13