Echelon LonMaker - Manual (Page 31)

LonMaker User’s Guide 15
The Glossary in Appendix G provides a quick reference for specific terms.
L
ON
W
ORKS
Networks
A L ON W ORKS network consists of intelligent devices (such as sensors, actuators, and controllers) that
communicate with each other using a common protocol over one or more channels. Network devices
are sometimes called nodes.
Devices
Each device includes one or more processors and a transceiver. The processor(s) provide the device’s
intelligence and implement a communications protocol. The transceiver serves as the device’s
electrical interface to the communications channel.
Devices communicate by publishing and subscribing to information on the network. The applications
on different devices are not synchronized, and thus it is possible that multiple devices may all try to
publish information at the same time. Meaningful transfer of information between devices on a
network therefore requires organization in the form of a set of rules and procedures. These rules and
procedures are the communication protocol, which is referred to as the protocol.
Protocol
The protocol defines the format of the messages being transmitted between devices, and it defines the
actions expected when one device sends a message to another. The protocol normally takes the form
of embedded software or firmware code in each device on the network. The protocol used on
L
ON W ORKS networks is defined by the ANSI/ CEA-709.1 (EN14908) standard. Echelon’s
implementation of this standard is called the LonTalk ® protocol. This document refers to the
ANSI/CEA-709.1 (EN14908) protocol as the LonTalk protocol, though all conforming
implementations of the ANSI/CEA-709.1 (EN14908) protocol are compatible.
Device Templates
A device template contains all the attributes of a given device type, such as its functional blocks,
network variables, and configuration properties.
Channels
A channel is the physical media between devices upon which the devices communicate. The LonTalk
protocol is media independent; therefore, numerous types of media can be used for channels: twisted
pair, power line, fiber optics, IP, and radio frequency (RF) to name a few. Channels are categorized
into channel types, and the channel types are characterized by the device transceiver. Common
channel types include TP/FT-10 (ANSI/CEA-709.3 twisted pair free topology channel), TP/XF-1250
(high-speed twisted pair channel), PL-20 (ANSI/CEA-709.2 power line channel), FO-20 (ANSI/CEA-
709.4 fiber optics channel), and IP-852 (ANSI/CEA-852 IP channel).
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
different channel types. Unlike other devices, routers are always attached to two or more channels.
Applications
Every device contains an application, which helps determine how a device functions. 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 the LonMaker tool.