Configuration and operation   
6.7 PROFINET IO mode 
  CP 443-1 Advanced (GX30) 
74  Manual, 03/2019, C79000-G8976-C256-05 
 
 
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). 
 
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. 
 
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.