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MG.60.N2.02 - VLT is a registered Danfoss trademark
VLT® 5000 / VLT® 6000 HVAC / VLT® 8000 AQUA
Message
Passing
Node
Arrangements LonWorks nodes can be addressed either
individuallyor in groups.A groupcan contain
up to 64 nodes, and one LonWorks network
can support 255 groups. Furthermore, any
node can be part of 15 different groups. A
subnet, very similar to a group, can contain
127 nodes. A domain is the largest
arrangement of nodes with a single domain
able to handle 255 subnets. Thus a domain
canhandle32,385separate nodes. A single
nodemaybeconnectedto no more thantwo
domains.
The group structure has the advantage of
allowinganumber ofnodestobereached at
only one address.This method reduces the
recordkeepinginsideeachchiptoaminimum,
allowing faster operation. However, high
efficiencyindividualaddressing can bedone
at all levels of a LonWorks system. The
address table of a node contains entries for
the group type and size and tells the node
howmanyacknowledgmentsto expectwhen
itsendsa message. It also tells the NEURON
chipwhichdomaintouseandthenodegroup
member number, which identifies an
acknowledgment as coming from the node.
Theaddress alsocontainsatransmittimer,a
repeattimer,a retrycounter,areceivetimer,
and the group ID.
There are a number of trade-offs between
network efficiency, response time, security,
andreliability.Generally,LonWorksdefaultsto
thegreatestdegreeof safetyand verification
forallcommunicationsovertheLONnetwork.
The LonTalk protocol, built into the chips, is
the operating system that coordinates the
LonWorks system. It offers four basic types
ofmessageservice.
Themostreliableserviceis
acknowledged
(or
end-to-endacknowledgedservice),wherea
messageissent to a node orgroupofnodes
and individual acknowledgments are ex-
pected from each receiver. If an
acknowledgmentisnotreceivedfromalldes-
tinations, the sender times out and re-tries
the transaction. The number of retries and
time-out duration are both selectable. Ac-
VLT LonWorks
Option Card The Danfoss VLT LonWorks option card is
comprised of a control card with a NEURON
chipanda memory card.When installed into
theVLT adjustable frequency drive, the unit
enablesthedrive to communicate with other
devicesontheLON.TheVLTdriveisdesigned
to provide precision control of standard
inductionelectricalmotors.Thedrivereceives
threereference signals along with start/stop
and reset commands from the network.The
drive also receivesa16-bitcontrolwordthat
provides full operational control of the drive.
(See
NetworkDriveControlInput
foradditional
details.)
In response, the drive provides 16 output
networkvariablescontaining important drive
and motor data. (See
Drive Feedback to
Network
.) Output to the network includes
drive status, current, voltage, motor and
inverter thermal status, and alarms and
warnings.
LonWorks supports many different types of
transmission media. A LonWorks network
physical layer option can be transformer
coupled twisted pair (78 kbps and 1.25
Mbps),freetopology,linkpower,powerline,
RF,RS-485, fiber optic,coaxial, or infrared.
The VLT LonWorks option supports four
transmissionmediawiththreeversionsofthe
VLT LonWorks option card. The VLT
LonWorksoption card versionsare:
1.Free topology, which also operates on
alinkpowernetwork.
2. 78 kbps transformer coupled twisted
pair.
3.1.25 Mbpstransformercoupled twisted
pair.
ArouterisrequiredtointerfacetoaLonWorks
network when not supported by one of the
threeoptioncard versions.