Image Processing Reference
In-Depth Information
The alarm and event handling services provide a wide range of options. Clients can subscribe to
change-of-value notifications (with variable increments) of any property. Notifications are also pos-
sible for further event types such as a binary or multistate input changing state or an analog input
exceeding a given range. Multiple event type algorithms may be applied to a single object, and even
property, at the same time. Devices can also send change-of-value reports unsolicited. Events can be
assigned different notification classes.
Remote device management services include services for dynamically discovering devices and
objects by way of their names or identifiers, discovering the network topology, as well as time
synchronization services.
In BACnet, devices have a large degree of freedom regarding which services and protocol fea-
tures they support. Details about which portions of the standard are implemented in a device are
documented in its protocol implementation conformance statement. To enable users to judge more
easily whether BACnet devices are interoperable, the standard defines BIBBs (BACnet Interoperabi-
lity Building Blocks). A BIBB describes certain capabilities in one of the five interoperability areas
data sharing, alarm and event management, scheduling, trending, device management, and network
management. Each BIBB consists of a client-server pair. his allows specifying precisely whether a
device requests a service, is able to answer such a request, or both. A BIBB can also imply the existence
of certain objects with certain properties. In addition, device profiles are speciied. hey describe col-
lections of BIBBs that map to the capabilities of typical BA equipment, such as “building controller,”
“smart actuator,” or “operator workstation.”
Interoperability testing and certification is performed by the BACnet testing laboratories (BTL),
which are associated with BACnet International and BIG-EU. he BACnet standard is being amended
continuously. Various addenda cover clarifications and protocol extensions as well as, e.g., improved
protocol security, object types (i.e., profiles) for lighting and security and load control, or ZigBee as
amedium.
∗
29.5.3 LonWorks
LonWorkswasinitiallydesignedbyEchelonCorp.asagenericbussystemforautomationpurposes.
Today, LonWorks technology is in widespread use for building automation purposes all over the
world. he LonWorks system consists of the LonTalk protocol, a tailor made processor (Neuron chip),
and network management software (LNS, LonWorks Network Services). By now, the LonTalk proto-
col is available as ANSI/EIA- [,] and EN []. In the following, the term control network
protocol (CNP) is used to refer to the standardized communication protocol as in these standards.
CNP supports a variety of different communication media and different wiring topologies. Since
it was designed as a generic control network, many protocol parameters are free to choose for the
designer. To achieve interoperability (see below), a number of communication
channel
profiles were
deined. hese still include a variety of TP, powerline (PL), and fiber optic channels. he most popular
channelforbuildingautomationpurposesisthe.kbpsfreetopologyTPproile(FT-),which
allows physical segments of up to m using low-cost TP cable. A variant providing link power
(LP-) is also available.
For the backbone, the IP tunneling method standardized in ANSI/EIA- [] (also known as the
IP- channel or
LonWorks/IP
) has largely replaced the fast TP variant (TP-) used before. Both
tunneling routers and fully IP-based IP- nodes are possible. Channel configuration data including
channel membership are managed by a central configuration server on the IP channel.
∗
BACnet/WS was also published as such an addendum.
