Lonworks; General Facts On Unigate ® Lonworks - Rs232/Rs485; Nodes; Network Variables (Nvts) - DEUTSCHMANN AUTOMATION UNIGATE IC - LONWorks Instruction Manual

LONWorks

9 LONWorks
9.1 General facts on UNIGATE
®
The UNIGATE LONWorks module communicates according to the LONTalk record. That means
that it can communicate with all LONWorks nodes which correspond to this record. For further
information on LONWorks technology see www.echelon.com and www.lonmark.org.
9.2

Nodes

Nodes are devices that interact with physically fixed control units and communicate via a net, that
features the LONTalk-protocol. Every node in the net contains stored intelligence that realizes
and carries out control functions (handling of the I/O signals). No central service or master-slave
construction is required and therefore a LONWorks net is often called "distributed I/O net".
Every node includes a physical interface, the transceiver of this interface with the communication
media. The UNIGATE
Echelon association. This is the medium usually mostly used in automation and this construction
supports the star, bus and loop wiring. The FTT-10A-transceiver is connected to the twisted bus
cable and has a baud rate of 78 kbit/s. The FTT-10A has a high impedance if no voltage is sup-
plied and it does not disturb the network communication if the operating voltage breaks down.
9.3

Network variables (NVTs)

A network variable is an object on a node that can be connected with one or several network
variables at one or several nodes. The network variable of a node defines its „input" and its „out-
put" from a network position and allows the sharing of the data in a distributed application. Every
time an application writes in one of its network output variables, the new value of the net vari-
ables is then distributed via the net to all nodes with the network input variables that were con-
nected with those network output variables. For example: In order to turn on the light via a
LONWorks-net, the net output variable of a switching node has to be logically connected to the
net input node of the lamp node. When the switch is activated, the network variable is distributed
via the net and it is received in the lamp node. The light is turned on. See picture below.
The LonMark Organisation accepted several net variables, that represent different ways of stan-
dard data illustrations e. g. temperature, pressure, percentage, voltage. They are called standard
network variables or SNVT's and they are listed in the "SNVT master and the programming man-
ual" of the Echelon association.
31 Instruction manual UNIGATE
®
LONWorks – RS232/RS485
®
-Lon-module uses the FTT-10A (Free Topology Twisted pair) from the
Deutschmann Automation GmbH & Co. KG
®
IC - LONWorks (62) V. 2.5 30.9.20