Echelon OpenLNS Commissioning Tool - Manual (Page 22)

6 Introduction
(high-speed twisted pair channel), PL-20 (ISO/IEC 14908-3 power line channel), FO-20
(ANSI/CEA-709.4 fiber optics channel), and IP-852 (ISO/IEC 14908-4 IP-communication).
Different transceivers may be able to interoperate on the same channel; therefore, each transceiver type
specifies the channel type or types that it supports. The choice of channel type affects transmission
speed and distance as well as the network topology.
Routers
Multiple channels can be connected using routers. Routers are used to manage network message
traffic, extend the physical size of a channel (both length and number of devices attached), and connect
channels that use different media (channel types) together. Unlike other devices, routers are always
attached to at least two channels.
Applications
Every L ON W ORKS device contains an application that defines the device’s behavior. The application
defines the inputs and outputs of the device. The inputs to a device can include information sent on
L
ON W ORKS channels from other devices, as well as information from the device hardware (for
example, the temperature from a temperature sensing device). The outputs from a device can include
information sent on L
ON W ORKS channels to other devices, as well as commands sent to the device
hardware (for example, a fan, light, heater, or actuator).
The application may be in the device when you purchase it, or you may load it into the device from
application files (.nld, .apb, and .nxe extensions) using OpenLNS CT.
Applications in devices are divided into one or more functional blocks. A functional block is a
collection of network variables and configuration properties that are used together to perform one task.
For example, a four-port digital input module may have four digital input functional blocks that
contain the configuration properties and output network variable for each of the four hardware digital
inputs on the device.
Network Variables
Applications exchange information with other L ON W ORKS devices using network variables. Every
network variable has a direction, type, and length. The network variable direction can be either input
or output, depending on whether the network variable is used to receive or send data. The network
variable type determines the format of the data.
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 OpenLNS CT 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: