Echelon IzoT Commissioning Tool - Manual (Page 23)

Network variables of identical type and length but opposite directions can be connected to allow the
devices to share information. For example, an application on a lighting device could have an input
network variable based on the SNVT_switch type, while an application on a dimmer-switch device
could have an output network variable of the same SNVT_switch type. A network management tool
such as the IzoT Commissioning Tool could be used to connect these two devices, allowing the switch
to control the lighting device, as shown in the following figure:
A single network variable may be connected to multiple network variables of the same type but
opposite direction. The following example shows the same switch being used to control three lights:
The application program in a device does not need to know where input network variable values come
from or where output network variable values go. When the application program has a changed value
for an output network variable, it simply assigns the new value to the output network variable.
Through a process called binding that takes place during network design and installation, the device is
configured to know the logical address of the other device or group of devices in the network
expecting that network variable’s values. The device’s embedded firmware assembles and sends the
appropriate packet(s) to these destinations. Similarly, when the device receives an updated value for
an input network variable required by its application program, its firmware passes the data to the
application program. The binding process thus creates logical connections between an output network
variable in one device and an input network variable in another device or group of devices.
Connections may be thought of as virtual wires. For example, the dimmer-switch device in the
dimmer-switch-light example could be replaced with an occupancy sensor, without making any
changes to the lighting device.
Configuration Properties
Configuration properties define how an application device behaves by determining the manner in
which data is manipulated and when it is transmitted. Configuration properties determine the functions
IzoT Commissioning Tool User’s Guide 7