FieldServer FS-8700-73 - Manual (Page 4)

FS-8700-73 BACnet MSTP Driver Manual Page 4 of 48
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1 BACNET MSTP DESCRIPTION
The BACnet Master-Slave/Token-Passing (MSTP) driver implements a data link protocol that uses the services of
the RS-485 physical layer. See the FieldServer BACnet PIC statement for the level of conformance that this driver
implements.
All information in a BACnet system is represented in terms of objects. The Object_Identifier is a 32-bit code that
identifies the type of Object (also identified by the Object_Type Property) and its "Instance" number, which
together uniquely identify the Object within its BACnet device. Theoretically, a BACnet device could have over four
million Objects of a particular type. The Object_Name is a text string, which has a unique capability. BACnet
devices may broadcast queries for devices that contain Objects with a specific Object_Name. This can greatly
simplify project setup.
BACnet requires one Device Object to be present in every BACnet device. The Device Object makes information
about the device and its capabilities available to other devices on the networks. Before one BACnet device starts
control-related communications with another, it needs to obtain some of the information presented by the other
device's Device Object. Unlike other Objects, the Device Object's Instance number must be unique across the
entire BACnet internetwork because it is used to uniquely identify the BACnet devices. It may be used to
conveniently identify the BACnet device from other devices during installation.
Standard object types are used to hold real time data and other information. Each Object Type is referenced by a
number, for example 0 represents an Analog Input.
Each Object consists of a number of prescribed properties, the main property being the Present_Value. Objects
are monitored and controlled through their properties. The Analog Input Object is representative of the Objects
involved directly with control elements and many of its Properties reflect this.
The information that follows describes how to expand upon the factory defaults provided in the configuration files
included with the FieldServer.
BTL Mark – BACnet Testing Laboratory
The BTL mark is a symbol that indicates to a consumer that a product has passed a
series of rigorous tests conducted by an independent laboratory which verifies that the
product correctly implements the BACnet features claimed in the listing. The mark is a
symbol of a high-quality BACnet product. For more information about the BACnet
Testing Laboratory go to: http://www.bacnetinternational.net/btl/.
Max Nodes Supported
FieldServer Mode Nodes Comments
Client
1
Server 32