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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 (D - F)

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



Destination Address

The logical address contained in every LonTalk® packet of the node or group of nodes designated to receive the packet. The destination address can be the unique Neuron ID, the logical node address, a group address, or a broadcast address.


Each device includes one or more processors that provide its intelligence and implement the protocol. Each device also includes a component called a transceiver to provide its electrical interface to the communications channel.

A device publishes information as appropriate to the application that it is running. The applications are not synchronized, and it is possible that multiple devices may all try to talk at the same time. Meaningful transfer of information between devices on a network, therefore, requires organization in the form of a set of rules and procedures.

Sensors, actuators, and controllers are examples of devices. See also LonWorks Device.

Device Discovery

Devices can be automatically discovered and commissioned using the Discover Devices command. This command allows the network management tool to search for devices on the network and match them to uncommissioned devices defined within the network. This allows the rapid commissioning of networks that have been designed off-site as described in Engineered System Scenario.

Device Name

The name given to the device file when saving it. It is recommended that a descriptive name is supplied for each LonWorks device.

Device State

The state of the target device. The device state is displayed in the NodeBuilder device window and the Neuron C debugger status bar. A device may be in the following states: bypass, flush, offline, online, preemption, and sleep.

Device Template

A template used by network management tools that contains all the attributes of a given device type (functional blocks, network variables, configuration properties, etc. Different device templates cannot share the same program ID.

Disabling Devices

Disabling a device disables all LonMark objects on the device. A device must be Online to be Enabled or Disabled.

Disabling FBs

The functional block will send its configured output network variable defaults. The device containing the functional block must be Online to use this command. To be disabled, a device must contain a LonMark compliant Node Object functional block. If Disable is selected and the device does not contain a Node Object, the device is put into the Offline state.

Device Interface File (XIF File)

A file produced by the LonBuilder Developer's Workbench or the NodeBuilder tool that documents a device's external interface (XIF). After converting the text version of the external interface file or XIF to binary using the utility, the host application can import external interface file definitions into the NSS using a set of services. The text version has an extension of XIF, the binary file has an extension of XFB.

The XIF file should not be be modified manually but it can be viewed using an application such as Notepad. Since the XIF file was originally generated from the application and matches the XIF within the device, changing the XIF will result in unpredictable behavior.

This file tells network-management tools how to communicate and recognize a device. It can be obtained from the device manufacturer’s website, it is included with the shipped product, it can be uploaded from the device (though without all of the file content), or it can be obtained from the LonMark site for each certified and published device. It contains Program ID, NVs, CPs, functional blocks, etc.  If the XIF is version 4 or later, it will contain default configuration properties.


A logical collection of devices on one or more channels.  Communications can only take place among devices configured in the same domain.

Domain ID

The top level of the LonTalk addressing hierarchy of domain/subnet/node.  The domain ID can be 0, 1, 3, or 6 bytes long.  The zero length domain is reserved for the use of the LNS architecture and cannot be used as the system's domain.


Data transfer from the host toward the network and the NSI.


An installation process in which data – such as the application program, network configuration, and/or application configuration – is transferred over the network to a device by a network management tool.

Downstream Device

The device receiving a network variable update.

Dynamic Data Exchange (DDE)

A standard Microsoft Windows® protocol that defines a mechanism for Windows applications to share information with one another. When applications share information with each other using DDE, they are said to be holding a DDE conversation.  Each conversation has a well-defined beginning, middle, and end.  To begin a conversation, one application, known as the client or destination application asks another application, known as the server or source application to open a communications channel.

Once a conversation is established, the client can send and receive data from the server on the DDE channel.  Note that the destination application is the one that establishes the conversation, irrespective of which way the data actually flows.


Electrically erasable programmable read-only memory. There are a limited number of write actions to EEPROM for a given controller.

Enabling Devices

Enabling a device enables all LonMark objects on the device. A device must be Online to be Enabled or Disabled.

Enabling FBs

Activates the functional block. 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.

Engineered System Scenario

The engineered system installation scenario allows the network to be designed without being connected to the physical network. Using Device Templates, devices can be added to one or multiple subsystems, configuration can be performed using plugins and binding can be created. Once the physical network is attached, these devices are associated with the physical devices through a simple commissioning step and all the configuration information is loaded into the devices and routers.

This is a common method for network design when the devices, configuration and programming is known before hand.


The mechanism that the NSS uses to inform a LNS host application of specific network activity, such as the arrival of a service pin message, or a change of network addresses. The LNS host application subscribes to and stops event notification using services.

Explicit Addressing

A form of messaging in which the device's application manually constructs messages and manually assigns an address to them.

Explicit Message

Low-level messages that Application Devices use to communicate with one another. Each message contains a message code that identifies the type of message. Application devices use the codes to determine the action to take when the message is received. When using explicit messages, the device is responsible for building, sending, and responding to messages.

Fan-In Connection

A connection where the outputs on multiple devices are directed to a single input on another device.

Fan-Out Connection

A connection where the output on a single device is directed to an input on multiple other devices.

FB (See Functional Block)


Firmware is programming inserted into programmable read-only memory (programmable ROM), thus becoming a permanent part of a computing device. Firmware is created and tested like software (using microcode simulation). When ready, it can be distributed like other software and, using a special user interface, installed in the programmable read-only memory by the user.

FMSI (Facility Master System Integrator)

An umbrella position within standard construction divisions to help oversee the specification and implementation of DDC systems. The FMSI is usually accountable for assuring Interoperability between sub-systems and different buildings, for providing a common Graphical User Interface and for assuring product from multiple bidder and vendors meets the intent of a specification as well as the letter of a specification and acts as a technical go-between for th various involved sub-trades (Controls, Electrical, Mechanical etc.).

Free Topology

A connection scheme for the communication bus that removes traditional transmission line restrictions of trunks and drops of specified lengths and at specified distances, and terminations at both ends.  Free topology allows wire to be strung from any point to any other, in bus, daisy chained, star, ring, or loop topologies, or combinations thereof.  It only requires one termination anywhere in the network. This can reduce the cost of wiring by a factor of two or more.

Full Client (see Remote Full Client or Local Client)

Functional Block

Applications in devices are divided into one or more functional blocks. A functional block is a collection of network variables and configuration properties, which are used together to perform one task. To define multiple functional blocks within a device, the device must contain a LonMark Node Object functional block, as defined by the LonMark Application-Layer Interoperability Guidelines.


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