Issue
What is the purpose of the Max Info Frames attribute in a Continuum BACnet controller?
Product Line
Andover Continuum
Environment
- BACnet MS/TP, MaxInfoFrames
- Optimizing MSTP
Cause
Information on the Max Info Frames function.
Resolution
The Max Info Frames setting on the BACnet controller object editor specifies how many messages that the controller can send out to other controllers when it has the token on the network. For instance, a B3 controller has a default of 2 for this setting. If it receives the token on the MSTP network and it has 5 COV or Event notifications to send to other controllers or workstations, it will send the first 2, and wait until it gets the token the next time around and send 2 more, etc.
The BCX controller has a default of 8 for Max Info Frames.
This setting is changeable through the BACnet controller editor, however care should be taken not to increase it to too large a number. The larger the setting, the more time that particular controller can hold the onto the token, which in turn denies other controllers on the network the capability of sending out their data in a timely manner. It should only be adjusted if there is a definite need for increased messaging, but on the MSTP network it is not recommended to go above 10, although we do not limit the value.
In a Cyberstation Version 1.8 or above the setting can be made on the details page of the BACnet controller device editor.
If adjustment of this parameter is done using any Cyberstation prior to version 1.8, the setting will not stay at the new value after a controller reload from the Infinity side, it will revert to it's default. You will need to create a PE program in the controller to set this parameter to the desired value if it is reloaded. The program should be autostart and fallthru, and use the "Writeproperty" keyword to set the parameter. The syntax should be as follows:
Line SetMaxInfo
WriteProperty ("Full Bacnet path name of controller", MaxInfoFrames, "New Value")
Stop
