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BACnet
Building Automation and Control Network (BACnet) protocol was developed under the auspices of the
American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) and is recognized
as an American National, European, and ISO global standard.
BACnet Device ID. All device IDs on a BACnet network must be unique. Refer to the section “Serial
Protocols” and refer to the Register List for additional information
The MD-xxHD Serial version supports writable max_master, MS/TP address, max_info_frames
properties in the device object for MS/TP networks. For best network performance, the
max_master should be set to the highest MS/TP MAC address on the network. The MS/TP
address (object 1069) must be unique on the MS/TP network. The max_info_frames does not
need to be changed in most installations.
Ethernet versions can register as Foreign Devices to a BBMD. BBMD stands for BACnet/IP
Broadcast Management Device. The BBMD IP address can be set from VIewpointHD or
through character string object 2264. A value of 0.0.0.0 disables foreign device registration.
This process requires a processor soft reset.
BACnet Segmentation
The MD-xxHD meter does not support BACnet Segmentation. Segmentation is required when the
requested data is longer than the underlying data packet size limitations of the protocol, ie the Maximum
Transmission Unit (MTU). The MTU for BACnet MS/TP is 480 bytes and for BACnet/IP it is 1476 bytes.
This means that some objects with large data arrays will not fit within a packet. This limitation effectively
means that some BACnet client software cannot read the Structured View Object List. In this case the
BACnet client structured view mode may need to be disabled and the standard flat object view will need
to be used instead, particularly with BACnet MS/TP.
BACnet Structured View
The MD-xxHD meter supports the Structured View (SV) object container. If this option is supported in the
BACnet exploring tool, objects will be grouped logically into elements which can be named to reflect
electrical or physical locations, followed by system objects, as shown below for a MD-12HD having
elements A-D.
Within each element, Structured View lists the BACnet objects by Object Type and then by numeric
number as shown below. In addition objects for elements are grouped in a “hotel room” scheme. That is
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