Technical Resources

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  Related Information

Device Certification - LonMark conformance instructions.

Design Guidelines - Technical information for developing open interoperable LonMark products.

Technical Corner - Provides answers to commonly asked technical questions.

LonMark Members who manufacture products used in Open Systems

Terminology (O - P)

The descriptions and terminology contained within this document are made in the context of use with LonWorks® networks and products.




This causes the application to stop running. In this state, the device will still respond to Online, Wink, and Test commands. An Offline device will still receive network variable updates, but the application will not process these values, and the device will NOT send network variable updates. If the device is reset while Offline, it will go Online after the reset.


The items managed by the NSS. The NSS treats the network as a collection of objects. Objects include nodes, programs, connections, network variables, message tags, and the system.


When a LNS® network design is unattached to a physical network or attached and the management mode is set to OffNet, changes to application and network configuration properties are saved in the database and propagated across the network. After being OnNet, network variables, such as temperature or enable/disable, can be changed on the network while working in OffNet mode (after devices have been commissioned and functional blocks added, connected, and configured).


The device’s state when its application is executing. A device must be Online to be Enabled or Disabled.


When a LNS network design is attached to a network and the management mode is set to OnNet, any changes made are propagated across the network immediately (after devices have been commissioned or functional blocks added, connected, or configured).

When working OnNet, the LNS Server interacts with the physical network and changes devices as the devices are changed in the network management tool. When working OffNet, the LNS Server can browse and test the devices on the physical network, but it will not make changes to the configuration of any devices.

Output Network Variable

A network variable that provides information from a device to other devices on the network.


OSI (Open Systems Interconnection) is a standard description or "reference model" for how messages should be transmitted between any two points in a telecommunication network. Its purpose is to guide product implementors so that their products will consistently work with other products. The reference model defines seven layers of functions that take place at each end of a communication. Although OSI is not always strictly adhered to in terms of keeping related functions together in a well-defined layer, most products involved in telecommunication make an attempt to describe themselves in relation to this model. It is also valuable as a single reference view of communication that furnishes everyone a common ground for education and discussion.

Developed by representatives of major computer and telecommunication companies beginning in 1983, OSI was originally intended to be a detailed specification of interfaces. Instead, the committee decided to establish a common reference model for which others could develop detailed interfaces that in turn could become standards. OSI was officially adopted as an international standard by the International Organization of Standards (ISO). Currently, it is Recommendation X.200 of the ITU-TS.

The main idea in OSI is that the process of communication between two end points in a telecommunication network can be divided into layers, with each layer adding its own set of special, related functions. Each communicating user or program is at a computer equipped with these seven layers of function. So, in a given message between users, there will be a flow of data through each layer at one end down through the layers in that computer and, at the other end, when the message arrives, another flow of data up through the layers in the receiving computer ultimately to the end user or program. The actual programming and hardware that furnishes these seven layers of function is usually a combination of the computer operating system, applications (such as the Web browser), TCP/IP or alternative transport and network protocols, and the software and hardware that enable a signal to be put on one of the lines attached to the computer.

OSI divides telecommunication into seven layers. The layers are in two groups. The upper four layers are used whenever a message passes from or to a user. The lower three layers (up to the network layer) are used when any message passes through the host computer. Messages intended for this computer pass to the upper layers. Messages destined for some other host are not passed up to the upper layers but are forwarded to another host. The seven layers are:

Layer 7: The Application layer...This is the layer at which communication partners are identified, quality of service is identified, user authentication and privacy are considered, and any constraints on data syntax are identified. (This layer is not the application itself, although some applications may perform application layer functions.)

Layer 6: The Presentation layer...This is a layer, usually part of an operating system, that converts incoming and outgoing data from one presentation format to another (for example, from a text stream into a popup window with the newly arrived text). Sometimes called the syntax layer.

Layer 5: The Session layer...This layer sets up, coordinates, and terminates conversations, exchanges, and dialogs between the applications at each end. It deals with session and connection coordination.

Layer 4: The Transport layer...This layer manages the end-to-end control (for example, determining whether all packets have arrived) and error-checking. It ensures complete data transfer.

Layer 3: The Network layer...This layer handles the routing of the data (sending it in the right direction to the right destination on outgoing transmissions and receiving incoming transmissions at the packet level). The network layer does routing and forwarding.

Layer 2: The Data-link layer...This layer provides synchronization for the physical level and does bit-stuffing for strings of 1's in excess of 5. It furnishes transmission protocol knowledge and management.

Layer 1: The Physical layer...This layer conveys the bit stream through the network at the electrical and mechanical level. It provides the hardware means of sending and receiving data on a carrier.

Override Off (FB)

Takes the functional block out of override. The functional block will now function normally. This command requires LonMark-compatible support for this operation in the device’s application. The device containing the functional block must be Online to use this command.

Override On (FB)

Puts the FB in override mode. Now the output network variables output their configured override value, even if part of the network is not yet operating and there is no input to the functional block. The override values are set using the functional block’s configuration properties.  This command requires LonMark -compatible support for this operation in the device’s application. See the documentation for the functional block being managed for more information on how to use override. The device containing the functional block must be Online to use this command.

Passive Configuration Tool

Can be any hardware or software that allows for configuring of a single device or set of devices without modifying the network. Plug-Ins used for network-management tools and platforms are the most common PCT.


A slot format for PC Cards of Type I, Type II, and Type III usually found only on notebook PCs. "PCMCIA" is a term that is no longer used. There are Type II PC Card interfaces available for connecting a PC to a LonWorks network.

PDF (Portable Document Format)

A file format used by LonMark to represent easily download-able paper-like digital versions of our profiles, types, and marketing information. It was created by Adobe Systems Incorporated and later, version 1.4 PDF/Archive (PDF/A-1), was standardized internationally as ISO 19005-1:2005 and corrected as ISO 19005-1:2005/Cor 1:2007. Other formats include PDF/E (ISO 24517), PDF/X (ISO 15930), and the ISO DIS 32000 for PDF version 1.7. LonMark may use any of these PDF formats in documentation made available to members and non-members.

Physical-Layer Repeater

A hardware device that connects two segments of a channel.  Unlike a LonWorks router, a physical layer repeater has no intelligence, so it cannot selectively forward packets to increase network capacity, and unlike a router, it forwards damaged packets. 

Physical Medium

A communication environment that carries the modulated signals from sources to destinations in a network. LonWorks networks support many media types, including twisted pair, power line, fiber optic cable, radio frequencies, infrared, and coax.

Ping Interval

The ping interval determines how often a device is pinged by the LNS Server to ensure it is still operating and in communication with the network.  Set the ping interval based on the expected attachment of the device to the network. If you expect that the device will never move on the network, select Never. Set the interval to 15 minutes for a device you expect will move rarely, to 2 minutes for a device you expect will move fairly often, and to 1 minute for a device you expect will move very often. The default ping interval is Never.

PL-20 Channel

A power line LonWorks channel type defined by ANSI/CEA-709.2 and EN14908-3.

Pre-Engineered Configuration

Configuration information is collected into a database at system design time by the network configuration tool, then is downloaded to the physical nodes later at network installation time.


An explicit request to a node for the value of one of its network variables.


A method of monitoring Network Variables. Periodically, as specified by the polling rate, the browser will request and display the value of a network variable. This capability is useful when the network variable value changes rapidly. If the network variable value changes rarely, polling causes unnecessary network traffic. The solution in this situation is to either reduce the polling rate or use bound monitoring. See also Bound Monitoring.


A mechanism provided by the LonTalk® protocol to allow devices priority access to a channel.

Private Media

A communications media that isn’t shared with other parties and uses 1 domain. See also Shared Media.

Program ID

The Program IDs can be displayed as either ASCII text, hex digits, or, if it’s a LonMark device, the standard program ID component details. Similar to the Neuron ID, the Program ID is hard coded into a device (in the Neuron Chip’s EEPROM) and cannot be changed by the user. Nodes with the same Program ID must have the same external interface.

When a device is defined in the network management tool, the following steps are performed:
1.   It looks up the device template name using a Program ID field. If the Program ID field is empty, it uses the TmplName user cell specified in the device shape (see Additional Device User Cells).  If a device template with that name is found, it is associated with the device shape.

If the device template specified in the TmplName or ProgramID user cell is not found, the tool looks for the external interface file specified in the XifName user cell. If the external interface file is found, the tool looks up the device template by the program ID specified in the external interface file. If a device template with a matching program ID is found, the user is given the option of changing the name of the device template to the name specified by the device shape, or using the existing device template name. In either case, the existing device template is associated with the device shape.

2.   If the device template is not found by the name specified in the TmplName user cell or the program ID specified in the external interface file but the external interface file is found, a new device template is created by importing the external interface file.  The new device template is given the name specified in the device shape, and is associated with the device shape.

3.   If the device template is not found by the name specified in the TmplName user cell or the program ID specified in the external interface file, and the external interface file is not found, the user is prompted to select an existing device template or to define a new device template by importing an external interface file.  The resulting device template is associated with the device shape.


A communication scheme defined by (i) services, (ii) data types handled by the services, and (iii) a state transition scheme for each device receiving or providing the protocol services. See also Communication Protocol.

Protocol Analyzer

A tool that can read every packet on a LonWorks channel.  A protocol analyzer is different from a device containing the complete LonTalk protocol stack in that it can receive every packet on the network, not just packets that are addressed to it.

Protocol analyzers allow users to observe, analyze, and diagnose the behavior of installed LonWorks networks.


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