Siemens SIMATIC ET 200AL System Manual page 1850

Dependencies
The length of the startup time for an IO device (distributed I/O) with the "Prioritized startup"
PROFINET function depends on the following factors:
• IO devices (distributed I/O)
• IO structure of the IO device (distributed I/O)
• Modules of the IO device (distributed I/O)
• IO controller
• Switch
• Port setting
• Cabling
• Configured RT class of the IO device
Note
Startup time and RT class of the IO device
An IO device with IRT communication requires longer than an IO device with RT
communication for the accelerated startup.
The longer startup for IRT is due to the necessity of synchronizing the IO device before the
communication can be set up.
Note
IWLAN and prioritized startup
PROFINET devices which are connected via access points to PROFINET IO do not support
the "Prioritized startup" PROFINET function.
PROFINET with STEP 7
Function Manual, 05/2021, A5E03444486-AL
Functions
5.13 Accelerating startup
285