Profinet Io Mode; How Profinet Io Devices Start Up In A Large Configuration; Reduce The Communication Allocation Reserved For Profinet Io When Operating Alongside Other Services; Prioritized Startup In Profinet Io - Siemens S7-400 Equipment Manual

Configuration and operation

6.7 PROFINET IO mode

6.7 PROFINET IO mode
6.7.1

How PROFINET IO devices start up in a large configuration

When operating the module with a large configuration (up to 128 communications
connections and up to 128 PROFINET IO devices), it may take several minutes when the
station starts up before all PROFINET IO devices have received configuration data from the
PROFINET IO controller. The IE/PB Link PN IO operating as a PROFINET IO device is particularly
affected by this.
To ensure that the CPU does not interrupt the distribution of project engineering data in this
situation, the parameter assignment monitoring time must be increased on the CPU.
Possible remedies: Reduce the size of the configuration (for example, distribution on several
CPs).
6.7.2 Reduce the communication allocation reserved for PROFINET IO when
operating alongside other services.
If cyclic data exchange over PROFINET IO is operating at the same time on the same Ethernet
subnet, set the communications allocation for PROFINET IO in the properties dialog of the
PROFINET IO system to a value <100%.
Reason: At the (default) setting 100%, the communication time is reserved primarily for
PROFINET IO data exchange. Reducing the communications allocation for PROFINET IO
increases the systemwide update time for PROFINET IO and creates additional time on the CP
for processing other communication services.
6.7.3

Prioritized startup in PROFINET IO

Functions
If you use RT or IRT communication, the CP supports the PROFINET functionality "prioritized
startup" for PROFINET IO devices that also support this function. A maximum of 32 PROFINET
IO devices can be configured per I/O controller. With these IO devices, simultaneous startup
times with values as low as 0.5 s can be achieved for a maximum of 8 devices.
Prioritized startup is used in fast processes when IO devices change quickly, for example fast
tool changes with a robot.
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Equipment Manual, 03/2023, C79000-G8976-C256-07
CP 443-1 Advanced