Installing a LONWORKS control network is greatly simplified over the traditional network approach. This is because the products use a standard protocol and are interoperable.
The installation process requires you to connect the devices to the physical media and describe which devices need to communicate to each other using installation tools and the information (network variables) to be communicated. You may also need to install a router to interconnect different communications media, extend the range of a network, or to isolate traffic on certain network channels.
Network installations may be divided into two stages:
Installing a device informs the network database that the device is on the network. This is usually done by pressing the service pin on the physical device and using software to recognize the device.
Binding a network variable tells the device which other devices it should talk to and what information it should share. This is where network variables specified by the device manufacturer are connected between different nodes.
The graphically based network management and control product to support LONWORKS applications can be a Windows® based software product suite (Windows 3.1x, Windows for Workgroups, Windows 95 and Windows NT) which is familiar and easy to use. Davmark Group can provide interfaces for the graphical creation and management of LONWORKS networks which provide all the functionality required to install, monitor and maintain LONWORKS networks.
To simplify message routing, the LonTalk protocol defines a hierarchical form of addressing using domain, subnet, and node addresses. This form of addressing can be used to address the entire domain, an individual subnet, or an individual node. In addition, multiple dispersed nodes can be addressed using domain and group addresses.
A channel is the physical transport medium for the LonTalk messages. Every node is physically connected to a channel. The communications medium can be twisted pair, power line, radio frequency, coax or fibre optic media.
A domain is a logical collection of nodes on part or all of one or more channels. Communications can only take place among nodes belonging to the same domain. Therefore, a domain forms a virtual network. Multiple domains can occupy the same channel. Domains may be used to prevent interference between nodes in different networks.
The user can choose which domains each node belongs to at the time of installation. For example, two adjacent buildings using nodes with RF transceivers on the same frequency would be on the same channel, but the installer could configure the nodes in each building to be in different domains to prevent interference between the applications. The user assigns the domain ID at the time of installation.
A subnet is a logical collection of up to 127 nodes within a domain. Up to 255 subnets can be defined within a single domain. All nodes in a subnet must be on the same channel, or on channels connected with bridges. Subnets cannot cross routers. If a node is configured to belong to two domains, it must be assigned to a subnet within each of the domains.
All nodes within a domain are typically configured in the same subnet except in the following cases:
Every node within a subnet is assigned a unique node number within the subnet.
Groups can also be assigned within a domain. A group is a logical collection of nodes within a domain, but the members do not have to share the same channel as with a subnet.
A node can be a member of up to 15 groups. Groups are an efficient way to use network bandwidth for one to many network variable and message tag connections.
A single domain can contain up to 256 groups.
Each node has a 48-bit unique ID assigned during manufacture. This ID is typically used as a network address only during installation and configuration. It may also be read and used by application programs as a unique product serial number. With 281,474,976,710,656 possible IDs, every node in a LONWORKS network is sure to have a unique address.
We hope this has been a useful introduction to Echelon Corporation’s LONWORKS® technology, and not too technical.
Davmark Group make things work. We do the hard work, not you.
Davmark Group provides advanced solutions using LONWORKS.
Extensive portions of this article were quoted verbatim
from Motorola document BR1108/D,
LONWORKS Product Line Brief
LonTalk Protocol. Davmark Group wishes
to express their grateful acknowledgment to both Echelon and
Motorola Semiconductor for these reference documents.