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Entry type: FAQ Entry ID: 109475919, Entry date: 05/27/2015
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With PROFINET IO via WLAN how do you set the update time and F-monitoring time in the TIA Portal?

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This entry demonstrates how to set the update time and F-monitoring time with PROFINET IO via WLAN in the TIA Portal.

PROFINET IO can also be run via WLAN. However, WLAN cannot provide the 100 Mbit/s full duplex transmission rates required by PROFINET. If multiple WLAN clients are logged on to one access point, they share the maximum data rate. The transmission rate per WLAN client drops. Because of this and the roaming between the access points you have to change the following PROFINET parameters for WLAN:

  • Update time
  • F-monitoring time with fail-safe communication

STEP 7 (TIA Portal) sets the update time by default to a small value, 2ms, for example. With PROFINET via WLAN you should change the update time to at least 64ms in order to enable stable operation.
The minimal update time, which are maximal possible, you find in the document "Industrial Wireless LANs in a PROFINET IO Environment" under the entry 22681042 

Setting the update time in the TIA Portal
Follow the instructions below to change the update time in the TIA Portal.

  • In the Network View of the Devices and Networks editor you mark the PROFINET IO system.
  • In the table area of the Devices and Networks editor:
  • You open the IO communication table and mark the IO device whose update time is to be changed. In the inspector window you get a display of the properties of the PROFINET interface of the IO device.
  • In the inspector window you open the "General" tab. In the area navigation, under "Advanced options > Real time settings" click the item "IO cycle".
  • For the update time you enable the option "Adjustable".
  • Set the required value for the update time.
       

Fig. 01

Test to see if operation is stable and further increase the update time if the IO devices fail often.

Note

  • With PROFIsafe via WLAN you must also change the F-monitoring time. The F-monitoring time should be set to six-fold the update time. A detailied calculation you find in the entries 58856512 and  93839056 
  • A fail-safe S7 connection via WLAN needs an even higher F-monitoring time. Set at least 2s.
  • The Safety-OB, e.g. OB35, must have a higher value as the PROFINET update time.

Setting the F-monitoring time in the TIA Portal
Follow the instructions below to change the F-monitoring time in the TIA Portal.

  • In the Network View of the Devices and Networks editor you mark the PROFINET IO controller. In the inspector window you get a display of the properties of the PROFINET IO controller.
  • In the inspector window you open the "General" tab. In the area navigation, you click the item "Failure safety".
  • For the F-parameter "Default F-monitoring time for central F-IO" you enter the required value.
       

Fig. 02

Further Information
Entry ID 109474533provides information about how to set the update time and F-monitoring time in STEP 7 V5.x.
Entry ID 92649989provides information about the configuration of a SIEMENS access point and a SIEMENS client.

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