LabSystem Network technologies LON® BACnet® Modbus® · 3 Network technologies Chapter 10.0 LabSystem Planning Manual Air technology for laboratories 1.1 What is LON? LON stands

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Network technologiesChapter 10.0

LabSystem Planning Manual ● Air technology for laboratories

10.0LabSystem

Network technologies ■ LON® ■ BACnet® ■ Modbus®

Table of contents

Section Title Page1.1 What is LON? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.1 Neuron® Chip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32.2 Lontalk® protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42.3 Transceivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42.4 Network extension in free topology . . . . . . . . . . . . . . . . . . . . . . . . 52.5 Network extension in bus / line structure . . . . . . . . . . . . . . . . . . . . . . 52.6 Maximum number of nodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.7 Repeaters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.8 Routers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.8.1 Routers as telegram fi lters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.9 LON and Internet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82.10 The object . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82.11 Binding (links) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82.12 Development tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92.13 Lonmark® and interoperability . . . . . . . . . . . . . . . . . . . . . . . . . . 92.14 Advantages of LON technology . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.1 Subsection-wide system . . . . . . . . . . . . . . . . . . . . . . . . . 9

4.1 SCHNEIDER Elektronik and LON . . . . . . . . . . . . . . . . . . . . . . . . . 9

5.1 LON network with connection to the Internet . . . . . . . . . . . . . . . . . . 10

6.1 What is BACnet? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116.1.1 The management level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116.1.2 The automation level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116.1.3 The fi eld level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116.2 Native BACnet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

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Table of contentsSection Title Page6.3 Interoperability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126.4 Data transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126.5 MS/TP (Master-Slave/Token-Passing) . . . . . . . . . . . . . . . . . . . . . . 136.6 EIA RS 485 Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136.6.1 Network extension in bus / line structure . . . . . . . . . . . . . . . . . . . . 13

7.1 Modbus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

8.1 SCHNEIDER Elektronik and networks . . . . . . . . . . . . . . . . . . 14

9.1 Short network dictionary A-Z . . . . . . . . . . . . . . . . . . . . . . . . . 15

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1.1 What is LON?

LON stands for Local Operating Network and was introdu-ced in 1990 by Echelon® Corporation (USA).

The LonWorks® technology is a very fl exible communica-tions system for building and process automation. It com-prises the communications protocol LonTalk, special hard-ware in the form of a Neuron Chip, and a range of tools for development, installation and maintenance of LonWorks networks and is thus a comprehensive platform for crea-ting LON automation networks.

The LonTalk communications protocol was standar-dised in 1998 in the American standard EIA-709.1 "Con-trol Network Specifi cation“ and in the European standard EN13154-2. All 7 layers of the ISO/OSI model are suppor-ted, which achieves the maximum possible fl exibility and performance in comparison with other fi eld bus systems. Table 7.6 (see page 11) shows the individual protocol lay-ers of the ISO-OSI model.

The networks consist of decentral intelligent devices called "nodes" and always include at least one neuron chip, which fulfi l the functions of a specifi c application process and can exchange messages on the basis of a common communications protocol.

LON devices (nodes) can communicate with one ano-ther on a wide range of different transfer media, among others:

Twisted pair cable, FTT-10A Powerline Fibre-optic Radio frequency RF Coax

The standardised transmission rates depend on the trans-mission medium used and range from 300 bit/s to 1.25 Mbit/s. In the area of building automation, LON networks with 78 kbit/s and the FTT 10-A transceiver are usually used.

The LonWorks® technology includes all resources re-quired for development, set-up, operation and mainte-nance, in particular:

Neuron® Chip as the hardware basis LonTalk® protocol as the communications protocol Various transceivers for physical coupling

with the transmission medium Development tool such as LonBuilder®, Node-

Builder®, LonMaker®, Pathfi nder® and others

2.1 Neuron® Chip

Neuron® Chip is a specially developed microprocessor (CPU) with a uniform, inexpensive communication con-nection for any type of technical application at fi eld or au-tomation level. Neuron Chips are available in two basic versions:

Neuron-3120 for devices with simple applications (one to three KByte application memory on the chip).

Neuron 3150 for devices with complex applications (up to 58 KByte external memory).

In addition to the two basic chips further versions are avai-lable, e.g. with larger EEPROM memory, integrated A/D converter, etc.

The 3120 and 3150 Neuron Chips have three indepen-dently functioning 8-bit processors (CPU) and support all 7 layers of the ISO/OSI model:

CPU 1 = Media Access Control CPU coordinates access to the transmission medium via the transceiver. CPI 1 implements layer 2 of the ISO/OSI mo-del.

CPU 2 = Network CPUis the network processor and is responsible, among other things, for transmitting network variables. CPU 2 imple-ments layers 3 to 6 of the ISO/OSI model.

CPU 3 = Application CPUis exclusively available to the application software of the technical application and thus implements layer 7 of the ISO/OSI model.

Data exchange between the processors takes place via common memory areas in the RAM.

Figure 10.1: Neuron Chip

CPU 1Media

Access

CPU 2

Network

CPU 3

Application

Network-Buffer Application-Buffer

Communicationinterface

Input/Outputinterface

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2.2 Lontalk® protocol

The communications protocol, which has been generally available since 1996 and is accessible to all, is known as the LonTalk® protocol.

It is the common LON language and is hard coded into the ROM of the neuron chip. This ensures that the protocol is always exactly the same, independent of the device ma-nufacturer. The LonTalk® protocol is the same for all no-des and guarantees the user compatibility of the devices.

The LON technology is the global standard for interopera-bility and more than 4000 manufacturers worldwide produ-ce devices and systems for the LonWorks® technology. All products have one thing in common: they can communica-te with one another and speak and understand the same language.

All SCHNEIDER products can be modularly retrofi tted with a network interface board. We support the LON®, BAC-net® and Modbus® networks, which ensures a very high level of fl exibility. 2.3 Transceivers

A LON network can be assembled with various transmis-sion media. The transceiver forms the link between the Neuron® Chip and the bus line (transmission media).

The FTT-10 A transceiver is the worldwide standard and enables connection to a two-wire line.

The main advantage of the FTT 10-A transceiver is the free network topology, i.e. retrofi tting in existing subsec-tions is easily possible.

Figure 10.2: Different network topologies

Table 10.1 shows the physical restrictions of the various transceivers.

Table 10.1: Different transceiver types

The transceiver type most commonly used in building au-tomation is the FTT 10-A in free topology. If cabling is car-ried out with the Belden cable, the maximum cable length is limited to 500 m. With the cable type JY(St)Y 2 x 2 x 0.8 the maximum cable length is limited to 320 m.

As soon as the recommended cable length is exceeded, a repeater or router must be installed in order to achieve a physical separation of the cable network and limit data traffi c to the absolutely essential data (router).

The LPT 10-A transceiver is equipped with an integrated power supply and generates 5 VDC with a maximum cur-rent load of 100 mA. This type is therefore ideal for actu-ating and supplying power to sensors and actuators. By means of a DC/DC transformer, the 5 VDC are generated from the actual LON data line, on which a direct current of 42 VDC is superimposed. Power supply and data transfer takes place via a single two-wire line and thus represents a very cost-effi cient solution

The FTT 10-A and LPT 10-A transceiver types can be used in parallel within the network topology, but the maximum number of nodes per segment is limited to 64 or 128.

The A and B bus wires of the LON cable can be connected in any way, i.e. irrespective of polarity and thus facilitate wiring, setup and troubleshooting.

In order to be able to use ring structures for retrofi ttings as well, we recommend ensuring correct polarity of the bus wires during the initial installation.

CAUTION!Only use cable type JY(St)Y 2 x 2 x 0.8 or

Belden 85102 or Belden 8471

Do not use cable type JY(St)Y 2 x 2 x 0.6!

CAUTION! If the network includes ring structures, the

correct polarity of the A and B bus wires must be ensured.

STARBUS/LINE

RING

FREETOPOLOGY

= LON-NODE

= BUSTERMINATOR

105 Ohm 105 Ohm

52,5 Ohm

52,5 Ohm

52,5 Ohm

TPT/XF-1250 1,25 M Bus 64 130m Trans isolated Industry, BackbonesFTT-10A 78 k Bus 64 2700m Trans isolated Building, IndustryFTT-10A 78 k Free 64 500m Trans isolated Building, IndustryLPT-10 78 k Bus 128 2200m Link Power Sensor, ActorLPT-10 78 k Free 128 500m Link Power Sensor, Actor

PRODUCT Bit rate(bps)

Topology Nodes per Cable Type Appliancesegment length

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2.4 Network extension in free topology

Figure 10.3 shows a typical LON network in free topology.

Figure 10.3: LON network in free topology

Depending on the cable type used, networks in free topo-logy achieve the following maximum values:

Table 10.2: Cable lengths in free topology

To ensure safe transfer in networks with free topology, the following points must be observed:

A terminator with R1 = 52.5 Ω or an LPT 10-A with integrated terminator must always be connected.

The distance from each transceiver to all other tran-sceivers may not exceed the maximum distance bet-ween two nodes.

In the case of different signal paths, e.g. with ring to-pology, the longest transmission path should be used as a basis for observation

The maximum cable length is the sum total of all net-work cables connected in the segment.

Connect shield on one side of RC to ground (R = 470kOhm, ± 5%, 0.25 W, C = fi lm capacitor 0.1 uF, ± 10%, ≥ 100V). Secifi cation and connection see LonWorks FTT-10A

Free Topology Transceiver User‘s Guide by Echelon.

Figure 10.4: Cable type JY(St)Y 2 x 2 x 0.8 in free topology

2.5 Network extension in bus/line structure

The special case of bus or line structures enables a con-siderable increase of the maximum permissible cable length. With this structure, the maximum possible cable length for FTT /LPT networks is achieved.

The bus line is laid in one strand. Connection of the nodes takes place via short stub lines (maximum 3 m). It is not necessary to ensure correct polarity of the bus wires.

Depending on the cable type used, networks that use bus/line structures achieve the following maximum values:

Table 10.3: Cable lengths in bus/line topology

FTT 10-A / LPT 10-A in free topologyCable types Max.

distance from node to

node

Max. total cable length

TIA 568A category 5 250 m 450 mJY(St)Y 2 x 2 x 0.8 320 m 500 mUL Level IV, 22 AWG 400 m 500 mBelden 8471 400 m 500 mBelden 85102 500 m 500 m

FTT 10-A / LPT 10-A in bus/line topologyCable types Max.

Length of the stub lines

Max. total cable length

FTT FTT/LPTTIA 568A category 5

3 m 900 m Not ap-plicable

JY(St)Y 2 x 2 x 0.8

3 m 900 m 750 m

UL Level IV, 22 AWG

3 m 1400 m 1150 m

Belden 8471 3 m 2700 m 2200 mBelden 85102

3 m 2700 m 2200 m

K

K K

K

K

K

K K

maximum 320 m

maximum 320 m

FTT 10-A / LPT 10-A, free topologywith cable type JY(St)Y 2 x 2 x 0,8

= Network node

= Busterminator = 52,5 Ohm

Maximum distance between any nodes: 320 m Maximum distance between any nodes and busterminator or LPT 10-A: 320 m Maximum cable length: 500 m

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To ensure safe transmission in networks with bus/line to-pology, the following points must be observed:

The bus line must be connected to bus terminators at both ends R1 = R2 = 105 Ω.

Optionally, instead of a bus terminator an LPT 10-A can be connected to the end of one bus line.

The second terminator is always required.

The maximum length of the stub lines must not ex-ceed 3 m.

When a physical repeater is used, a maximum of 5400 m can be achieved.

Figure 10.5: Cable type Belden 8471 and Belden 85102 in bus/line topology

Table 10.4 lists the cable specifi cations for the various ca-ble types. The cable type JY(St)Y 2 x 2 x 0.8 is widely used in Europe and can be supplied from stock, while the Belden cable is produced in the USA and thus has longer delivery periods. The Belden cable is considerably more expensive than the JY(St)Y cable.

Table 10.4: Cable specifi cations for various cable types

2.6 Maximum number of nodes

Irrespective of the topology and the selected cable type, the following rules apply for the connection of FTT 10-A and LPT 10-A to a bus line segment:

maximum 64 FTT nodes per bus line segment

maximum 128 LPT nodes per bus line segment

In the case of mixed assembly with FTT and LPT:• maximum 128 nodes per segment• LPT counts as single• FTT counts as double (greater load on the bus)

Note on cable type JY(St)Y 2 x 2 x 0.8Maximum total length of the bus line: 900 mMaximum length of the stub lines: 3 mWith screen cables, the screen should be connected on one side (no earth loops) via an RC element to earth (R = 470 Ω, ± 5 %, 0.25 W, C = fi lm capacitator 0.1 μF, 10 %, ≥ 100 V)

Sample calculations:

1. 100 LPT nodes, 10 FTT nodes: 1 x + 2 x 10 = 100 + 20 = 120 → permissible

2. 30 LPT nodes, 40 FTT nodes: 1 x 30 + 2 x 40 = 30 + 80 = 110 → permissible

FTT 10-A / LPT 10-A in bus/line topologyCable types Con-

ductor diameter

AWG Conduc-tor

cross-section

Rloop Ω/km

TIA 568A category 5

0.51 mm 24 0.21 mm2 28

JY(St)Y 2 x 2 x 0.8screened

0.80 mm 20.4 0.503 mm2

73

UL Level IV, 22 AWGunscreened

0.643 mm

22 0.324 mm2

106

Belden 8471unscreened

1.29 mm 16 1.31 mm2 28

Belden 85102unscreened

1.29 mm 16 1.31 mm2 28

K

K

max. 2700 m (FTT) or 2200 m (FTT/LPT)

FTT 10-A / LPT 10-A in Bus- / Linetopology with cable type Belden 8471

= Network node

= 2 x Busterminator = 2 x 105 Ohm

Maximum distance between busterminator with FTT-Transceiver: 2700 m Maximum distance between busterminator with FTT/LPT-Transceiver: 2200 m Maximum length of stub line: 3 m Distances only valid for bus- or line topology

K K K K K

max. 3 m

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2.7 Repeaters

A network segment is restricted to 64 nodes (when FTT transceivers are used). If a project requires more than 64 nodes, a further network segment is installed. The indivi-dual network segments are connected to one another with repeaters and/or routers.

Repeaters are devices with two bus connections. In the case of the maximum number of nodes (=64), one node must be subtracted for the repeater, i.e. a network seg-ment comprises a maximum of 63 connected subscribers (nodes). The task of the repeater is consists of accepting data telegrams from the bus side, amplifying them and sending them to the opposite side.

Repeaters are used:

when the maximum network extension of a segment has been reached

when the maximum number of nodes in a segment is exceeded.

Repeaters have no fi lter function and simply forward each telegram they receive. Thus the data traffi c of a network segment passes unhindered into the adjacent segment. Too much data traffi c results in irregular delays in the re-sponse time. With repeaters it is only possible to connect two network segments with the same transceiver family, while routers also allow the connection of different trans-mission media.

A maximum of three repeaters can be switched one after another in a logical chain. After this, a router is necessa-ry for regeneration of the data telegram. After the router, again a maximum of three repeaters can be connected, etc.

Figure 10.6: Repeaters as data signal amplifi ers

2.8 Routers

Routers also have two bus connectors and therefore, like repeaters, can be used for signal amplifi cation. Routers can be equipped with two different transceivers and thus can connect different transmission media, e.g. twisted pair segment with power-line segment (TP ↔ PL) or media with different transmission speeds, e.g. twisted pair with 78kbit/s with twisted pair with 1250 kbit/s (TP 78 ↔ TP 1250).

2.8.1 Routers as telegram fi lters

However, the main area of application is the telegram fi l-ter functionality, whereby specifi c telegrams do not reach other network segments if no subscriber is addressed the-re. This reduces data traffi c to the necessary minimum and increases the response time of the entire system. During the "fi lter function", the data telegram remains within its own network segment, while during the "forwarding func-tion", the data telegram reaches other network segments.

The router is therefore mainly used for logical structuring of the network.

Figure 10.7: Network structuring with routers

max. 63 Nodes

Repeater as Amplifier

To increase the maximum number of Nodes Maximum three Repeater in a row; then one Router; then again maximum three Repeater in a row etc.

RepeaterK

KK

K

K

K

K

K

K

K

K K

K

K

K

KK

1 Node

max. 63 Nodes

1 Node

K K

Networksegment 1FTT 10-A, 78 kbit/s

Networksegment 2FTT 10-A, 78 kbit/s

max. 63 Nodes

Network with Router

Logical network structurizing Visualizing, Control and Remote maintanance via BMS Interconnection between LON-Segments with different Transceivertypes

K

K K

K

K

K

K

K

K

K

K K

K

K

K

KKmax. 63 Nodes

Segment 1Router

1 Node 1 Node

K K

Router1 Node 1 Node

K K

K K

KK

Router1 Node 1 Node

K K

Segment 2

Segment 3

BuildingManagement

System

8



2.9 LON und Internet

A large number of manufacturers offer Internet servers with an LON interface. This makes Internet access to LON nodes possible from any subsection.

Thus remote maintenance and diagnostics and alarm no-tifi cations are easily possible via the Internet, which consi-derably increases the reliability of the entire system. The required data security is guaranteed by means of authen-tication. This is a password-controlled procedure on the basis of a random generator. A randomly generated 64 bit number is compared by the transmitter and the receiver and, if the coding is the same, the receiver recognises whether the transmitter is authorised and accepts or re-jects the package.

Figure 10.8: Internet server

2.10 The object

Each node is described by an object (functional unit). Fi-gure 10.9 shows a typical general graphical description. Objects represent the network interfaces of an application or parts of the application of a node in relation to other nodes or objects. LonMark defi nes the node object and fi ve general objects that should be used in applications:

Open loop sensor object Closed loop sensor object Open loop actuator object Closed loop actuator object Controller object

The object itself is represented by a rectangle with roun-ded corners. Input variables are shown as arrows on the left-hand side (nvi#) and output variables as arrows on the right-hand side (nvo#).

Figure 10.9: General representation of an object

2.11 Binding (links)

The logical links between the individual nodes are defi ned in the binding. The nodes provide their data to the network in the form of network variables. In the binding the output network variable (nvo#) of the transmitting node is linked to one or more input network variables (nvi#) of one or more receiving nodes, which ensures accurate data ex-change. Table 10.5 shows an extract of the network varia-bles list (SNVT) for the FC500 fume hood controller of the LabSystem series.

Table 10.5: Extract from the SNVT list for FC500

Schneider LabSystem parameter list for the FC500 fume hood controller according to the SNVT master list 10.0 Binding compatible network variables Date 01.01.2003

SNVT / SCPT / UNVT / UCPTNo. Name No. Name Value range Unit Data type Description1 nviZyklus 87 SNVT_elapsed_tm 0 .. 65535 Timer Setpoint for the transmission cycle

actual value

2 nviBetrieb 83 SNVT_state 0 .. 65535 16 bit status Input of the operating mode, see at-tachment for the meaning of the bits

3 nvoBetriebFB 83 SNVT_state 0 .. 65535 16 bit status Output of the operating mode, see attachment for the meaning of the bits

4 nvoStatus 83 SNVT_state 0 .. 65535 16 bit status Output of status messages, see at-tachment for the meaning of the bits

5 nvoAlarm 22 SNVT_lev_disc On / Off Switch Alarm notifi cation

6 nvoIst_Volumen 15 SNVT_fl ow 0 .. 65534 [ l/s ] 2 byte integer Volume fl ow actual value

nvi# SNVT nvo# SNVT

Object Name and Number

MandatoryNetwork Variables

nvi# SNVT nvo# SNVTOptionalNetwork Variables

Configuration Properties

ManufacturerDefined Section

Hardware Output

Hardware Input

InputNetworkVariables

OutputNetworkVariables

Typenvi

nvo

nci

nro

Descriptionnetwork variable input

network variable output

network configuration properties

network read only

Storage classRAM

RAM

EEPROM

ROM

nci#

9



2.12 Development tools

The development tools are used for creating neuron pro-grams in the programming language Neuron-C and for set-up of individual nodes as well as entire networks (bin-ding).

2.13 Lonmark® and interoperability

The LONMARK® Interoperability Association creates func-tional profi les and the SNVT master list (Standard Network Variable Type). Devices and systems that are developed in accordance with these rules achieve a very high level of interoperability. Interoperability means the ability to carry out a task in a distributed application with devices produ-ced by different manufacturers.

During product development, SCHNEIDER specifi cally fol-lows the SNVT master list and thus achieves a high level of interoperability and fl exibility for the operator.

2.14 Advantages of LON TECHNOLOGY

The following summarises the advantages of LON tech-nology:

Decentralised automation

Sensors and actuators are equipped with their own intelli-gence (CPU) and directly exchange the relevant informa-tion with one another. Information processing takes place directly, eliminating the need for central processing.

Reduced investment costsdue to minimum wiring effort (twisted pair cable) and mul-tiple usage of actuators and sensors.

Reduced operating costsdue to system and subsystem-wide usage of information as well as the implementation of fl exible control strate-gies.

Reduced maintenance and servicing costsdue to common, system-wide diagnostic possibilities as well as system-wide central building management.

Flexibility of retrofi ttingLON technology is extremely fl exible with regard to chan-ges and enhancements to functionalityand retrofi tting. Thanks to the use of free network topolo-gy, manufacturer-independent products can be connected directly.

Building transparencyA very high level of building transparency for the operator is achieved through the capture of operating costs and re-mote monitoring and diagnostics, even via the Internet.

Open to the future

Through the use of manufacturer-independent products, continuous development of the application technology is guaranteed.

3.1 Subsection-wide system

The LonWorks® technology offers a cost-effi cient solution for operating buildings as subsection-wide systems. Sen-sors and actuators of different subsections, such as elec-trical and sanitary installations, heating, ventilation and air conditioning, sun protection and access control, can be used by all subsections.

In addition to considerable savings on investment costs, fl exibility and usage levels are increased.

4.1 SCHNEIDER Elektronik and LON

We have been developing and producing products with LonWorks® technology since 1996, we have implemented numerous large projects and have excellent references.

The interoperability and the increasing acceptance world-wide have convinced us. This is why we actively and en-thusiastically participate in the LNO (LON user organisa-tion).

10



5.1 LON network with connection to the Internet

Figure 10.10 shows an entire LON network in free topo-logy. All LON nodes, including the FC500-V-L fume hood controllers and the LCO500 laboratory controller are im-plemented with FTT-10A or LPT-10 transceivers.

With the LCO500 laboratory controller, cost-effi cient mixed systems can be implemented, in which analogue actua-tion occurs within the laboratory, while the LCO500 can be connected to the LON network outside the laboratory. In the case of data access through to the fume hood, the laboratory controller only occupies one node of the LON

network, which considerably reduces the number of rou-ters required.

In addition to the automatic balancing function for room supply air and room exhaust air, the LCO500 laboratory controller can actuate digital inputs (alarms, sensors, etc.) and digital relay outputs (light, motors, etc.) via the LON network. Remote maintenance of the fume hoods and their controllers is also possible via the Internet or an intranet.

With the remote maintenance software PAD3000, SCHNEI-DER offers the entire functionality from a single source.

Figure 10.10: LON network with Internet connectionRemote maintenance

Service

INTERNET

INTRANET

INTERNET

LON-ETHERNETRouter

ETHERNET

INTERNET

LON-network

Measuretemperature

Digital output

Control

Monitoring

Display

Measurepressure

Digital input

Alarm

LON-INTERNETWeb-Server

Building management system

In-houseremote maintenance

LonWorksApplication

Lab controllerLCO500


Control


FC500

Fume hoods

FC500

Fume hoods FC500

Fume hoods

Display

Measuretemperature

11



6.1 What is BACnet®?

BACnet® stands for Building Automation and Control network and is a manufacturer-independent network pro-tocol (data transfer protocol) for building automation.

The development objective of the BACnet® protocol was to provide a uniform, company-independent standard for data communication, that is, a technical terminology for data exchange, in and with building automation systems. BACnet® has been a standard of ASHRAE (American So-ciety of Heating, Refrigerating and Air-Conditioning Engi-neers) since 1995 and was taken over as an ANSI-Norm (135). BACnet® has also been an ISO standard (16484-5) since 2003.

6.1.1 The management level

The BACnet® protocol should be used as a standard at management level in order to enable joint control, regulati-on and monitoring even in the control centres of large, he-terogeneous building automation systems. Administration of the systems should be done with BACnet®.

6.1.2 The automation level

At the automation level one level below, in addition to BACnet® other protocols such as LONTalk®, PROFIBUS and Modbus are possible. Gateways are used to connect the different networks (e.g. LON and BACnet) with one another. However, these "mediators between two worlds" are not always without problems, because protocol trans-lations in gateways are usually not perfect.

6.1.3 The fi eld level

One level further down is the fi eld level with the connected fi eld bus modules. Here access to the physical parame-ters, such as retrieval and setting of digital and analogue inputs and outputs, is established via the corresponding interface. If protocol standards other than BACnet are used, here as well gateways must be installed between the different networks.

The level model is displayed in Figure 10.11.

Figure 10.11: Level model

6.2 Native BACnet®

Native BACnet® is when the "BACnet® operating stack", i.e. the communication software, is implemented directly on the microcontroller, that is, when the fi eld modules can communicate directly via BACnet® without external hard-ware components (e.g. physical gateways). In this respect, native Bacnet® is a standardised communication protocol, a universal "mother tongue" used from the management level through to the fi eld modules at fi eld level.

Figure 10.12: Connection of different networks

FC500

Fume hoods

Field levelStandard:BACnetLonMarkPROFIBUSEIBModbus

Standard:BACnetLonMarkPROFIBUS

Standard:BACnet

Management level

Automation level


FC500

Fume hoods

BACnet

BACnet Devices

GATEWAYBACnet

LON

LONField level

Management level


12



This eliminates the need for additional technology (gate-ways) and the costs that these incur and improves system performance and interoperability.

Figure 7.12 shows the connection of two different networks (LON with BACnet). In this example, native BACnet® is not implemented at fi eld level, i.e. a protocol transforma-tion of the LON and BACnet protocols takes place in the gateway.

However, here the hardware costs at fi eld level are higher. A very powerful CPU (central processor unit) must be used in order that the BACnet® data communication can easily be handled by an independent task.

For economic reasons, it should be decided from project to project whether it is absolutely necessary to communi-cate with native BACnet® right down to the fi eld level.

With its retrofi ttable bus modules, SCHNEIDER offers the complete BACnet, LON and Modbus service solution down to fi eld level, i.e. down to the fume hood.

Figure 10.13: Retrofi tting of a LON bus module

6.3 Interoperability

BACnet ensures interoperability between the devices of different manufacturers, provided that all partners involved in the project agree upon specifi c BIBBS defi ned by the standard. A BIBB (BACnet Interoperability Building Block) defi nes which services and procedures must be supported on the server and the client side in order to implement a specifi c requirement of the system.

The PICS (Protocol Implementation Conformance State-ment) document that belongs to the device and is produ-ced by the manufacturer lists all supported BIBBs, object types, character sets and communication options.

The fi ve BACnet interoperability classes (IOC) defi ne va-rious services that are used for communication between building automation devices. These services are divided into the following classes:

Data sharing, DS Alarm and event management, AE Scheduling, SCHED Trending, T Device and network management, DM

The standard defi nes various object types as well as pro-cedures for alarm processing.

With the aid of the BIBB list and the PICS (Protocol Imp-lementation Conformance Statement), the planner of an interoperable system can check whether interoperability will be achievable.

6.4 Data transport

BACnet® offers various media for data transport, which guarantees a high level of fl exibility of the entire system.

Table 10.6 summarises the various media together with the specifi c standards and transmission speeds.

Table 10.6: Extract from the SNVT list for FC500

The transmission speeds of the individual media are sor-ted from top to bottom. The same applies to the costs per node (fi eld module). Ethernet is the fastest data transmis-sion with max. 100 Mb/s, but here the highest costs per node are incurred.

ARCNET is too expensive for fi eld modules (low end cont-rollers), but it does offer very good speed potential.

LonTalk with the FTT-10A transceiver and a transmission rate of 78,4 kB/s is an acceptable solution, however, it has the following disadvantages: dependency on one compa-ny and licence costs per node.

BACnet data transportLAN Standard Speed in kB/sEthernetTCP/IP

ISO/IEC 8802-3 10,000 - 100,000

ARCNET ATA/ANSI 878.1 156 - 7,500LonTalk EIA/CEA 709.1-B 4.8 - 1,250MS/TP EIA RS 485 9.6 - 76.8PTP EIA RS 232-C 9.6 - 56

13



6.6.1 Network extension in bus / line structure

The bus line is laid in one strand. Connection of the no-des is done via short stub lines (maximum 5 m). Always install the twisted pair (A and B) individually. It is essential to ensure the correct polarity of the bus wires.

To ensure safe transmission in networks with bus/line to-pology, the following points must be observed:

The bus tine must be connected to bus terminators at both ends R1 = R2 = 120 Ω.

Connect shield to ground on one side.

The second terminator is always required.

The maximum length of the stub lines must not ex-ceed 5 m.

The maximum cable length is 500 m.

A maximum of 32 subscribers may be connected to a bus/line structure.

Figure 10.14: EIA RS 485 in bus/line topology

Figure 10.14 shows the bus/line topology of the EIA RS 485 standard with the maximum cable lengths.

In table 10.7 various cables suitable for the EIA RS 485 Standard are specifi ed.

MS/TP (Master-Slave/Token-Passing) is the best compro-mise for fi eld modules. The max. data transmission speed of 76.8 kB/s is suffi cient for most applications and the EIA RS 485 interface can be implemented as a low cost solu-tion. However, some restrictions concerning the network structure must be taken into account and adhered to. Free topology, as with LON, is not possible.

6.5 MS/TP (Master-Slave/Token-Passing)

The Master-Slave/Token-Passing protocol was also deve-loped by ASHRAE and is only available for BACnet.

Connection to the fi eld bus is done via the inexpensive EIA RS 485 interface. MS/TP can be operated in pure Master/Slave mode, with token passing between equal partners (peer to peer token passing method) or with a combination of both these methods.

6.6 EIA RS 485 Standard

The EIA RS 485 standard defi nes a bidirectional bus sys-tem with up to 32 subscribers. Because several transmit-ters operate over a shared line, a protocol is required to ensure that a maximum of one data transmitter is active at any time (e.g. MS/TP). All other transmitters must be in a state of high impedance during this time.

In the ISO standard 8482 the cabling topology is standar-dised to a max. length of 500 metres. The subscribers are connected to this bus cable in line topology via a max. 5 metre long stub line. It is generally necessary to terminate the cable at bothe ends with terminating resistors (2 x 120 ohm) in order to prevent refl ections.

If no data transfer takes place (data transmitter inactive), a defi ned quiescent level should arise on the bus system. This is achieved by connecting line B via 1k Ohm to earth (pull down) and line A via 1k Ohm to +5V DC (pull up).

Although intended for large distances in industrial environ-ments, where potential shifts cannot be avoided, the EIA RS 485 standard does not prescribe galvanic separation. However, since the receiver components are sensitive to shifts in earth potentials, galvanic separation, as defi ned by ISO9549, is recommended for reliable installations.

During installation it is essential to install the twisted pair (A and B) individually. It is also essential to ensure correct polarity of the twisted pair, because incorrect polarity can result in inversion of the data signals. Particular in the case of problems with the installation of new end devices, trou-bleshooting should begin by checking the bus polarity.Always install screened cables in line (daisy chain) topolo-gy and install the screen on one side.

max. 500 m

EIA RS 485 in Bus- / Line topology(daisy chain)

Maximum distance between busterminator: 500 m Maximum length of stub line: 5 m Use always drilled shielded cable. Only bus-/ line topology allowed.

max. 5 m

120

120

1 k

1 k

+5V

GND

Wires drilled.Cable shielded.

A

B

A B

Fieldmodule

A B

Fieldmodule

A B

Fieldmodule

A B

Fieldmodule

max. 5 m

1 2 3

max. 32Field modules

14



Table 10.7: Cable specifi cation for various cable types

All cables must be screened.

7.1 Modbus

Modbus is an application protocol developed in 1979 by Gould-Modicon for exchanging messages between fi eld modules with integrated Modbus controllers.

The Modbus protocol is located on the application layer of the OSI reference model and supports master/slave ope-ration between intelligent devices.

The Modbus protocol defi nes the message type via which the Modbus controllers communicate with one another. It describes how a Modbus controller establishes access to another controller via a query, how this query is answered, and how errors are recognised and documented.

The Modbus protocol works on a query-response basis and offers various services, which are specifi ed by func-tion codes. During communication, the Modbus protocol determines how each controller learns the device address and recognises messages that are intended for it. In addi-tion, it determines which actions are to be carried out and which information the Modbus controller can extract from the fl ow of messages. When a response is required, this is assembled in the controller and sent to the corresponding station with the Modbus protocol.

The implementation of Modbus via EIA RS 485 is inexpen-sive and is therefore suitable for internal laboratory net-work connections. When laying the cables, it is essential to adhere to the standards described in section 6.6.

EIA RS 485 in bus/line topologyCable types Manufac-

turerConductor diameter

[mm]

AWG Conductor cross-section

[mm²]

Rloop Ω/km

Max. cable length of the bus line [m]

Li2YCYPiMF Lapp 0.80 20.4 0.503 78.4 500JY(St)Y 2 x 2 x 0.8screened

Various 0.80 20.4 0.503 73 300

9843 paired Belden 24 78.7 500FPLTC222-005 Northwire 22 52.8 400EIB-YSTY Various 1.0 0.80 31.2 500

8.1 SCHNEIDER Elektronik and networks

Because fi eld bus modules for LON, BACnet and Modbus can be retrofi tted at any time, the entire system is very fl exible and can be cost-effectively adapted to various net-works.

We offer the entire system from a single source, without compatibility problems.

15



9.1 Network dictionary A-Z

AAddress, also called Neuron ID, is a Neuron Chip identi-fi cation number (48 bit address) that is unique worldwide and is assigned during production (hardware address). Among other things, it serves to identify the node during set-up and is sent to the LON network by pressing the service key.

BBACnet® is a standardised protocol of ASHRAE (Ame-rican association of HRA manufacturers). BACnet uses, among others, LON® as a transport medium, however, important, useful characteristics (particularly the use of network variables) are thereby lost.

BatiBUS was one of the fi rst fi eld buses in the area of building automation and is prevalent mostly in France. The transmission speed is 4800 bit/s and simple, twisted pair cabling is used as a transmission medium.

Binding is the logical link between individual nodes. The binding determines which data is to be exchanged bet-ween the nodes. The nodes provide their data to the LON network in the form of network variables. During binding, the output variable (nvo) of the transmitting node is lin-ked to one or more input variables (nvi) of one or more receiving nodes. This is how a defi ned data exchange is assigned.

Bridges transfer the messages to the other side when the source domain of a message corresponds to one of the bridge domains, independent of the target of the message. A bridge is used for connecting domains, e.g. for forwar-ding system messages intended for all subsections.

CChannel Networks are physically structured by routers and repeaters - they divide the network into several chan-nels. Channels denote a physical network segment, e.g. a bus segment in TP/FT-10. Taking into account the physical limitations of the underlying medium, any number of nodes may belong to a channel.

Confi gured Routers transfer a valid message to the other side when the source domain corresponds to one of the router domains. Each side of the confi gured router has its own transmission table for this purpose. In this table, for each of the 255 possible subnets and each of the 255 groups of a domain, the transmitters that are to send a message are marked with a transmission fl ag. These ta-bles are generated by a network management tool and permanently saved in the router EEPROM.

Using a confi gured router is recommended when the net-work traffi c should be purposely separated. This results in islands with relatively high internal network traffi c and relatively little external communication. This means that the entire system is not burdened with messages of purely "local" character.

CSMA is an access procedure from the LAN area and stands for Carrier Sense Multiple Access. With CSMA, the node fi rst "listens" in the network before becoming active. With CSMA/CD (Collision Detect), collisions are expected from the start and if possible counteracted with various processes.

LonWorks functions with predictive p-persistent CSMA processes, which enables short response times with high throughput rates even in large networks.

DDomains are the largest addressing units. They are used to implement subsystems that are fully independent of one another, e.g. lighting system, access control (insofar as these do not have to communicate with one another). Thus domains are virtual networks within the physical net-work construction. Each device can be addressed via two domain addresses. A maximum of 255 subnets each with 127 devices (corresponding to a total of 32,385 devices) can be assigned to a domain.

EEchelon® is the technology supplier of the LONWORKS technology. In December 1990 Echelon announced its developments internationally for the fi rst time. The capital for this innovative and risky development was provided by venture capitalists in the USA, among others the semicon-ductor manufacturers Motorola and Toshiba. Echelon's In-ternet address is http://www.echelon.com.

EIB The European Installation Bus was further developed for building automation technology and emerged from In-stabus, an installation technology standard. The transmis-sion rate is 9600 bit/s and a screened two-wire line is used as a transmission medium.

Ethernet is local area network (LAN) technology and is widely used in computer networks. Data transfer between the computer systems takes place at a speed of 10 and 100 million bits per second (Mbps). Coaxial cables, twisted pair cables and fi bre-optics are used as a transport medi-um. Ethernet is the most frequently used LAN worldwide and enables manufacturer-independent computer networ-king.

FFree Topology is a network topology that fi rst became possible with the FTT10 transceiver. In free topology, line, star or ring structures can be combined with one another. This means than when planning networks, it is no longer necessary to take linear bus structures, with their relatively short stub lines, into consideration. However, it is essential to adhere to the maximum transmission distances, which, depending on the cable quality, are easily reached. The-se limits can be overcome through the use of routers or repeaters.

16



GGroups are another form of addressing that is indepen-dent of the domain subnet node addressing. Up to 255 groups per domain can be formed, whose members can all be addressed through the group addressing. Any num-ber of devices can be a member of each group, but each device can only be a member of max. 15 groups.

IIndustrial Ethernet builds on Ethernet and is increasin-gly becoming established at fi eld bus level. However, the costs for the fi eld bus subscribers (nodes) are currently still very high. An advantage is the high data transmission rate, which enables fast reaction in real time.

Interoperability is the objective and defi ning attribute of the LONWORKS technology. Independent of the selected transmission medium, network topologies, hardware de-tails or operating system functions, LONWORKS nodes should be able to "play" with one another. In fact, it is lar-gely irrelevant whether data is exchanged, for example, via 78 kBit/s twisted pair or via RS485. At the application program level, one does not notice these implementation details. The developer of a LONWORKS-based system can for the most part view and defi ne the design levels hardware - software - communication structure - physical network independently of one another.

ISO-OSI model is a model developed by ISO (Internatio-nal Organisation for Standardization) for communication between nodes in networks. This model was named OSI (Open System Interconnection) and is based on the 7 communication layers described in table 10.8.

LLearning Routers are a special type of confi gured router. All messages are transmitted with group addressing. At the same time a learning process is active. After a reset, all transmission fl ags are set and thus all messages are transmitted. The learning router checks the subnet num-ber of each incoming message and deletes the transmis-sion fl ag on the other side, so that over time two transmis-sion tables develop, as with confi gured routers. However, these tables are only stored in RAM, so are lost after each reset. However, the tables can be read out and edited with an appropriate tool, so that afterwards the router can be run as a confi gured router. Learning routers are not as powerful as confi gured routers; however, they can be in-stalled without knowledge of the network topology and the communication structures.

LNO LON NUTZER ORGANISATION e.V.LNO (LON user organisation) is an association for compa-nies, institutions and distributors who work with the LON-WORKS technology in German speaking areas. Anyone who develops, sells or uses devices and systems that use the LonTalk® protocol can become a member. Members may be legal persons, partnerships or natural persons whose home, offi ce or institute is situated in the Federal Republic of Germany, Switzerland, Austria, Holland, Bel-gium or Luxembourg.

The LNO is a registered association which is conducted in accordance with German associations law. Current infor-mation about the LNO and a list of members is available at http://www.lno.de.

Layer Description Functionality7 Application Layer Communication services for the application6 Presentation Layer Language and character settings5 Session Layer Session start-up and shut-down, subscriber identifi cation4 Transport Layer Connection and disconnection of end-to-end connections, fl ow control3 Network Layer Routing2 Data Link Layer

Data storage layerFrame alignment, point-to-point data storage, media access control

1 Physical LayerBit transmission layer

Specifi cation of all physical and mechanical parameters

Table 10.8: ISO-OSI model

17



LNS/LCA "LONWORKS Networks Services Architecture"/"LONWORKS Component Architecture". A software plat-form developed by Echelon with functional and data inter-faces for the implementation of tools for LON, e.g. for hand terminals, operating stations, for PC visualisation and PC projection tools.

LON® is the abbreviation for Local Operating Network. The development objective of Echelon was an 8-bit microcont-roller, similar to an 80C51, which was expanded to include hardware units for on-chip networking. The LON designers had recognised that the greatest development effort in dis-tributed systems lies in the design of the communication interfaces. However, the developer should think about his task and not about the implementation of data exchange between processors and operating systems.

LonBuilder® is the high-end development system of the company Echelon. With LonBuilder, you can emula-te hardware, compile application software and test it af-ter download. Modules can be made downloadable using Flash-EEPROMs.

LONMARK® Association is an international association of more than 200 companies which undertake the standar-disation of LON for specifi c tasks and devices, with the aim of ensuring interoperability. The content is developed by the LONMARK Task Groups. Thus there are standards (functional profi les) for louvre control, lighting, sensors, actuators, among others. Information about the status of activities can be found at http://www.lonmark.org.

LonTalk® is the protocol through which the Echelon sys-tem solution is specifi ed. LonTalk defi nes how LON no-des on the individual levels of the ISO-OSI model com-municate with one another. LonTalk describes hardware, operating system and compiler functions precisely, while the implementation remains hidden - the developer should implement his application and not levels 1 to 7.

LONWORKS® is the system name for the entire techno-logy. This includes, for example, the Neuron® chips, the bus connection elements (transceivers), the development tools, software packages, suppport. With LONWORKS, decentralised information processing structures are pos-sible that can operate without central control (e.g. SPS). This is what makes LONWORKS different from previous fi eld bus solutions.

LPT-10 Link PowerThis transmission medium is also a version of twisted-pair. Technically it corresponds to the version "free topology FTT10", with the additional advantage that the supply vol-tage of the devices can also be transmitted via the bus line. This eliminates the need for a pair of wires in the ca-ble and also reduces the danger of confusion during con-nection (which is bus, which is current?). LPT-10 is LON-MARK certifi ed.

There are no advantages without disadvantages: LPT-10 requires the use of special Link Power supplies (input vol-tage e.g. 48 - 56 V, output voltage about 42 V/1,5A), which are usually not exactly cheap. Switch cabinets or devices often have a 24 volt power supply anyway, in addition to the 230 volt voltage level. Thus with Link Power, an addi-

tional voltage supply level is necessary. In addition, there are limits regarding the load-bearing capacity - a Link Po-wer power supply can only supply a limited number of de-vices (this is important, for example, for devices with light-emitting diodes or relays, which often have a higher power requirement). The main advantages lie in easier wiring of sensing devices and switches in the building. Link power signals can be switched on TP/FT-10 devices, if these in-clude the corresponding block condensers, which block off the supply voltage.

Note: An economic effi ciency calculation regarding the use of LPT-10 is necessary. Dimension the power supplies accurately and include enough reserves for the worst case situation for all devices in the segment! Check the LPT-10 compatibility of TP/FT-10 devices.

MModbus® is a standardised protocol of Gould Modicon and was developed in 1979. It is an industrial standard, but in future it will be replaced by more effi cient standar-dised protocols (e.g. BACnet).

NNetwork variable see NV

Neuron-C is the programming language in accordance with the ANSI-C standard for application programming of Neuron Chips. Neuron-C includes additional operating system functions for event-driven programming and for network variables for process-oriented programming, as well as more complex objects for I/O interfaces.

Neuron Chip is a specially developed microprocessor (CPU) with a uniform, inexpensive communication con-nection for any type of technical application at fi eld or au-tomation level.

Neuron ID see Address

Node is the name for a device or a component with a Neuron chip as a microcontroller, possibly also with exter-nal memory and I/O functionality. Nodes are the smallest addressing unit.

NodeBuilder® is a low-end development system from Echelon. See LonBuilder®.

NV‘s (network variables) are type-specifi c variables in the Neuron-C programming language for the implementation of logical communication channels between nodes.

18



PPLT-21 is a transceiver for Power Line data transmission. In addition to the possibility to transmit data via the normal 230 volt network or other voltaged lines, the PLT-21 recei-ver can also send and receive data via voltage-free lines. This is particularly useful when lines that are no longer used have been laid, but these do not meet the specifi cati-ons for the application of FFT-10 transceivers. Particularly in public power supply networks, Powerline transceivers should be used responsibly. Sources of disturbance that could interfere with the transmission band of the PLT-21 may appear to the transceiver to be an occupied band and thus in the worst case completely prevent communication. Even an old PC with a faulty switching power supply can cause complete disruption of a network.

In such cases, the PLT-22 transceiver offers the possi-bility to automatically change to a different transmission frequency. However, this should only be regarded as a chance to reduce transmission confl icts; in a public power supply network that is characterised by constantly chan-ging conditions, it does not provide a guarantee.

Power Line provides data transmission via the 230 volt network in accordance with CENELEC. Various manuf-acturers offer routers that make it possible to change to Power Line.

Prog-ID Each device includes a special software that im-plements the application. A device may be delivered with various software (function versions, etc.). The PROG-ID is used to differentiate between these versions. It is a cha-racter string that is stored in a specifi c place in the memo-ry. Projection tools use the PROG-ID to differentiate bet-ween devices with the same hardware but with different functions. LONMARK has defi ned instructions as to how the PROG-ID should be coded and used.

RRepeaters are physical amplifi ers without their own pro-cessing functions. They are used to achieve greater trans-mission distances or when the maximum number of nodes exceeds 64 devices per twisted pair segment.

Note: In TP/FT-10 networks, only one physical router may be placed between two nodes. Otherwise, routers should be confi gured and used in the same way as repeaters. The repeater counts as a node, so that per segment 63 nodes + 1 repeater can be used.It is also possible to use routers as repeaters. This elimi-nates the restrictions imposed by physical repeaters and also makes it possible to change media.

Routers connect adjacent subnets, whereby the router works with addresses and protocols of Layer 3. This layer is hardware-independent, so that routers are capable of switching to another transmission medium. Routers can be operated in the operating modes Repeater, Bridge, Learning Router and Confi gured Router. Unlike physical repeaters, routers that are confi gured as repeaters are not subject to the limitation that only one repeater may be placed between two nodes.

SService Pin is a special input/output on the node that is used for service purposes. This pin is usually connected by the module manufacturer to an external button and an LED on the outside of the device. When the service button is pressed, the Neuron Chip sends a broadcast message containing the Neuron ID and the program ID. In this way, a node can be logged onto a tool, for example, (assign-ment of a physical node to a logical node in the project). As an output, the service pin signals the current status of the Neuron (application and confi guration) and thus enables basic diagnostics.

SNVT (Standard Network Variable Type) are type-specifi c variables in the Neuron-C programming language for the implementation of logical communication channels bet-ween LON nodes. They have been standardised by the LonMark Association.

Subnets are, after the domain, the next smallest addres-sing unit. With subnet addressing, specifi c groups of de-vices (e.g. those in a room or a manufacturing cell) can be addressed. Subnets can contain a maximum of 127 devices.

TTerminators enable correct impedance termination of a network on the basis of twisted pair technology. Depen-ding on the transceivers and topology used (bus or free topology), different terminators should be used in accor-dance with the Echelon specifi cation. Terminators are also sometimes integrated in devices and can, as a rule, be activated via switches or jumpers. Lack of termination or incorrect termination of a network does not necessarily have an immediate, obvious effect; however, it may be the cause of infrequently occurring communication problems.Terminators in accordance with the specifi cation are avai-lable as ready-to-use components. Networks in free topo-logy are terminated with a terminator (52.5 Ω). Networks in bus/line topology are terminated with a terminator at both ends (2 x 105 Ω).

TP/XF-78 Twisted Pair 78 kBit/secIn the initial LON years, this transmission media with trans-mission coupling was very common. Up to 64 devices can be connected to a segment in line bus topology - the de-vices are lined up like a pearl necklace. The length of the bus line of a segment can be up to 2000 m. TP/XF-78 is LONMARK certifi ed.

Note: TP/XF-78 should no longer be used for new deve-lopments.

19



TP/XF-1250 Twisted Pair 1250 kBit/secTP/XF-78 was introduced at the same time as TP/XF-1250. This is also a line bus with transmission coupling with up to 64 devices per segment, but is limited to a length of 130 m ... 400 m. The considerably higher physical transmis-sion rates only marginally increase data throughput and response time. Thus, with a few exceptions (e.g. in time-critical backbone buses in switch cabinets or for special transmission tasks with large data packages), applications are limited, particularly because special requirements are made with regard to the details of the topology.

Caution! TP/XF-1250 is not LONMARK certifi ed!Follow the special wiring instructions exactly! TP/RS-485 Twisted Pair RS-485In the early days of LON, various device manufacturers tried to reduce the costs for the transceivers to an absolute minimum by using RS-485. However, there are in fact pro-blems with RS-485, e.g. problems with galvanic separation and with directing the earth reference potential between different devices. The implementation of CE-compliant RS-485 interfaces in practice involves the same effort as with other twisted pair versions. For this reason, Echelon no longer supports RS-485.

TP/FT-10 Twisted Pair Free Topology TP/FT-10This is without doubt the most common transmission me-dium nowadays. The TP/FT-10 channel allows both line bus topology and free topology. Again, 64 subscribers can be connected to a segment of up to 2700 m as a line bus. The transmission rate is 78 kBit/sec. In free topolgy it is possible to achieve network extension of up to 400 m with 64 devices. TP/FT-10 allows the greatest degree of free-dom regarding the physical positioning. TP/FT-10 is LON-MARK certifi ed.

Transceivers are the bus connecting elements between the Neuron Chip and the transmission medium. The most important examples are: TP/XF-78, TP/XF-1250, TP/FT-10, LPT-10, LPT-10 and PLT-21. In addition, transceivers are available for wireless transmission or for coupling with fi bre optic systems.

WWink is the ability of a node to draw attention to itself in various ways (visually, audibly, etc.) after it has received a wink message. This enables an installation tool to search for unconfi gured nodes in a network and to send a wink message to the fi rst node that answers. If provision is made for this in the node's application, the node draws attention to iself in a defi ned way, so that the technician can establish an allocation to the physical node.

20



Documents

LabSystem Network technologies LON® BACnet® Modbus® · 3 Network technologies Chapter 10.0 LabSystem Planning Manual Air technology for laboratories 1.1 What is LON? LON stands