7
MG.60.N1.22
- VLT is a registered Danfoss trademark
VLT
®
5000 / VLT
®
6000
HVAC / VLT
®
8000 AQUA
Message
Passing
Node
Arrangements
LonWorks nodes can be addressed either
individually or in groups. A group can 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
can handle 32,385 separate nodes. A single
node may be connected to no more than two
domains.
The group structure has the advantage of
allowing a number of nodes to be reached at
only one address. This method reduces the
record keeping inside each chip to a minimum,
allowing faster operation. However, high
efficiency individual addressing can be done
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
how many acknowledgments to expect when
it sends a message. It also tells the N
EURON
chip which domain to use and the node group
member number, which identifies an
acknowledgment as coming from the node.
The address also contains a transmit timer, a
repeat timer, a retry counter, a receive timer,
and the group ID.
There are a number of trade-offs between
network efficiency, response time, security,
and reliability. Generally, LonWorks defaults to
the greatest degree of safety and verification
for all communications over the LON network.
The LonTalk protocol, built into the chips, is
the operating system that coordinates the
LonWorks system. It offers four basic types
of message service.
The most reliable service is
acknowledged
(or
end-to-end acknowledged service), where a
message is sent to a node or group of nodes
and individual acknowledgments are ex-
pected from each receiver. If an
acknowledgment is not received from all des-
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 N
EURON
chip and a memory card. When installed into
the VLT adjustable frequency drive, the unit
enables the drive to communicate with other
devices on the LON. The VLT drive is designed
to provide precision control of standard
induction electrical motors. The drive receives
three reference signals along with start/stop
and reset commands from the network. The
drive also receives a 16-bit control word that
provides full operational control of the drive.
(See
Network Drive Control Input
for additional
details.)
In response, the drive provides 16 output
network variables containing 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), free topology, link power, power line,
RF, RS-485, fiber optic, coaxial, or infrared.
The VLT LonWorks option supports four
transmission media with three versions of the
VLT LonWorks option card. The VLT
LonWorks option card versions are:
1. Free topology, which also operates on
a link power network.
2. 78 kbps transformer coupled twisted
pair.
3. 1.25 Mbps transformer coupled twisted
pair.
A router is required to interface to a LonWorks
network when not supported by one of the
three option card versions.
