Lon Works Network Overview; Table 1-2. Supported Topologies - GE 90*-30 PLC Series User Manual

L W Network Overview
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Catalog No.
PE693BEM350
PE693BEM351
PE693BEM352
GFK-1322A
A control network consists of intelligent control devices, called nodes, that communicate using a
common protocol. Each node in the network contains embedded intelligence that implements the
protocol and performs control functions. In addition, each node includes a physical interface that
couples the node's microcontroller with the communications medium.
In a L W network, the nodes communicate over one or more media such as twisted wire
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pair, power line, fiber optic cable, coaxial cable, RF, or infrared. At the heart of each node is the
®
Neuron chip which contains the L
protocol that ensures that nodes can interoperate using an efficient and reliable communications
standard. Because Neuron chips can be connected directly to the sensors and outputs that they
supervise, a single Neuron chip will process sensor/output status, execute control algorithms, and
communicate with other Neuron chips.
The L T protocol uses I/O points, known as network variables, to allow devices from
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different manufacturers to communicate with each other. Echelon's Standard Network Variable
Types (SNVTs) provide standard units of measurement for common control quantities, such as
pressure, temperature, and volume. The LBIM supports SNVTs that are less than 32 bytes in
length, and are defined in The SNVT Master List and Programmers Guide (005-0027-01).
The LBIM contains a transceiver that provides a physical communication interface between the
module's Neuron chip and a L
based on the TP/XF-T78 and TP/XF-1250 transceivers, and free topology, based on the TP/FT-10
transceiver. The free topology allows more options for network design. Table 1-2 lists the
topologies supported by each type of LBIM. Figure 1-2 illustrates the supported topologies.

Table 1-2. Supported Topologies

Transceiver Topology
TP/FT-10 Free
(Bus, Star, Loop,
Others, Combinations)
TP/XF-78 Bus/Loop
TP/XF-1250 Bus/Loop
Chapter 1 Overview
T protocol, a complete seven-layer communications
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W network. The LBIM supports bus and loop topologies,
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Bit Rate: 78Kbps
Distance: 500m free topology, 2,700m with doubly
terminated bus. Distance can be multiplied with
repeaters.
No. of Nodes: up to 64
Other: Transformer-isolated; high impedance when
unpowered
Bit Rate: 1.25Mbps
Distance: 500m (0.3m stubs)
No. of Nodes: up to 64
Other: Transformer-isolated
Bit Rate: 78Kbps
Distance: 2000m (3m stubs)
No. of Nodes: up to 64
Other: Transformer-isolated
Network Characteristics
1
1-3