TECO F510 series - Bacnet Protocol Descriptions; Bacnet Services

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4.7 BACnet Protocol Descriptions
BACnet is in compliance with four-layer of seven-layer structure models in OSI (Open Systems
Interconnection) of International Standard Organization (ISO). These four-layer structure models
are application layer, network layer, data link layer and physical layer. Besides, BACnet is definced
by the view of standard “object” and “property.” All BACnet devices are controlled via the property of
objects. Every controller with BACnet devices is considered an object collector so that every
controller device can execute different kinds of functions of objects to achieve the communication
control and monitor control.
4.7.1 BACnet Services
Services provide some commands to save or control information and some functions to achieve
the purpose of monitoring and control. Namely, one BACnet device reveive certain information or
command to complete specific work from other BACnet device so the two devices need to support
the same service to complete communication. To complete the exchange of these service
messages, these communication requirements are specified in the communication protocol of
application layer by BACnet. Thus, services are parts of the communication protocol data unit
(PDU) in the application layer and build the communication modes via the relationship of Server –
Client. Client will send the message of sevice requirements to Server and Server needs to respond
to Client to execute this service. Refer to the following fugure.
Application
Layer
Network Layer
Data Link Layer
Physical Layer
Application Layer of BACnet
Network Layer of BACnet
ISO- 8802-2
(IEEE802.2)
ISO- 8802-3
(IEEE802.3)
ARCNET
MS/TP PTP
EIA-485 EIA-232
LonkTalk
OSI Corresponding ModelBACnet Simple Model
Request for PDU
R esp o n d to P D U
Receive
SendReceive
Send
Request Respond
Client Server