Distech Controls ECB-VAV, User Manual

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34 Network Guide
Controller) to the highest Master device's MAC Address number to optimize the efficiency of
the data bus.
Setting the Max Master and Max Info Frames
The Max Master and Max Info Frames are parameters used to optimize a BACnet MS/TP
Data Bus. This is set in the Data Bus Master (EC-BOS Building Controller) for the MS/TP port
of the Data Bus Master and for each BACnet MS/TP device connected on that port.
A Configure MS/TP Devices tool is available to automate this task. This tool:
• Can only be used with a live database during commissioning. If you add more devices to
the data bus, you must run this tool again.
• Automatically calculates the value for the Max Master by finding the highest Master device
MAC Address on the connected BACnet MS/TP data bus plus 1.
• Sets the Max Master for all master devices including the Data Bus Master (EC-BOS).
• Sets the Max Info Frames for all master devices excluding the Data Bus Master (EC-
BOS).
For the Data Bus Master (EC-BOS), set the Max Info Frames to 20 in the screen shown in
Figure 21 as this is a device that will make more requests for service from other devices on the
network. In general, according to the way a device is programmed, the Max Info Frames may
have to be set to a higher value than for other devices. For example, when Roof Top Unit Con-
trollers are used with VAV controllers that use gfxApplications code, they should also have
their
Max Info Frames set to a higher value such as 5, as Roof Top Unit Controllers will poll
many VAV controllers for information.