BECKHOFF DK9222-0411-0038 User Manual

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Application Note DK9222-0411-0038

I/O, Building Automation

Keywords

KL6401
TwinCAT
Building Automation
KS2000
LON
Line coupler
SNVT
Transceiver

Integration of LON networks into a PC-based building
automation system

This application example from the ’Building Automation Sub-bus Systems’ series conveys the basic

principles of LonWorks (LON for short) and the integration of LON devices into the PC-assisted building

automation system via the Beckhoff KL6401 LON Bus Terminal. LON is a local sensor/actuator network in

which the devices communicate directly with one another via network variables (SNVTs). The typical area

of use of LON is the trade-spanning automation of functional buildings, in which the modular structure

of LON allows flexible changes and conversions. Besides the KS2000 configuration software for the

parameterization of the SNVTs, the LON user requires a LON tool in order to establish the ’binding’ between

the individual devices.

1. LON

LonWorks (Local Operating Network: LON for short) is a decentralized network for intelligent sensors, actuators and operating

devices with a large field of application; its main use is in the automation of functional buildings. Through transmission media

such as twisted pair wires, sensors and actuators can communicate with one another as desired from any point to any other

point on the basis of network variables (SNVTs, Standard Network Variable Type). Each LON device contains a microprocessor,

the neuron, which controls the communication. Each neuron has a unique identification number, the neuron ID, which

corresponds to the physical address and is set in the factory.

LON is typically used for trade-spanning networking within the building automation; a LON network consists of up to 32,000

intelligent network nodes. LON is an international standard on account of its widespread use worldwide. It is mainly used in

the automation of functional buildings, since devices developed by different manufacturers from different systems and trades

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Application Note DK9222-0411-0038

I/O, Building Automation

can be integrated in one system. Further areas of application are industrial and process automation, supply and disposal,

energy technology, traffic control, etc.

2. Master versions

LON is a typical multi-master system, in which each device on the bus can have event-controlled transmission. The neuron

controls communication

3. Topologies

LON is a classic line bus, but it can follow any topology. Since it is possible to choose between star, ring, tree or classic line

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structures, this often gives rise in practice to free topologies that are oriented to existing structures in buildings or plants. The

following are used for segmenting such free topologies:

Repeater | for physical amplification with no processing function

–

– Router | for the connection of subnetworks

– Bridges | connection of domains

LON devices communicate via different transmission media; as a result, the range of a LON network depends directly on the

transmission medium. If all guidelines are taken into account in the topology structure, a LON network can have a virtually

unlimited size. With the classic TP wiring (twisted pair – two-wires twisted together) the maximum bus length is 1300 m.

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max. 63 nodes

max. 63 nodes

repeater

router

max. 127 nodes + 1 repeater

subnet

r

outer

r

outer

repeater

router

max. 255 subnets per domain, each with 127 nodes = 32385 devices

Application Note DK9222-0411-0038

I/O, Building Automation

.1 Network structure

3

A LonWorks network is divided into the domain, subnet and nodes. There may be a maximum of 255 subnets (subnetworks) in

the domain – a subnet in turn may consist of a maximum of 127 nodes (LON nodes). Additionally, a domain may consist of a

maximum 32385 LON nodes, i.e. LON devices. Several domains can be connected if necessary. In principle, however, only nodes

within a domain can communicate directly with one another. Each node in a network has a unique logical address, which is

divided into these three hierarchical levels: Domain ID, Subnet ID and Node ID.

Fig. 1 Structure of LON networks

Components such as routers, bridges and repeaters are used for the construction of LON networks.

Repeaters are physical amplifiers with no processing function. They are used to achieve greater transmission distances and/or

to extend the maximum permissible number of nodes of 64 nodes per 2-wire segment when using FTT-10-transceivers.

Routers are devices with several bus connections, which are used to interconnect several subnetworks. Telegrams received on

one side are normally transmitted again on the other side by the router – and vice versa, of course. The router can also perform

the function of a filter, a pathfinder or a post distributor.

4. Communication

LON nodes communicate directly with one another on the basis of the LonTalk® protocol, without going through a central

control unit. Data exchange takes place by means of SNVTs: they form the logical interface between two nodes. SNVTs consist

of three sections: unit, range of values and resolution, which must be configured identically in both nodes for unambiguous

interpretation of the data.

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