Files which define the network visible interface for one or more LONWORKS devices are known as LONMARK device interface i.e. XIF files.
It is basically an interface to a device which is exposed over a LONWORKS network. It only exposes the inputs to the algorithms and the outputs from the algorithms and does not expose the internal algorithms of a device. A device interface contains following information:
- Device’s self documentation information
- Number of address table entries
- Number of message tags
- Number, types, and directions of network variables.
The device interface can be inquired over the network to a great extent with the help of a network tool. The device manufacturer establishes the completeness of a queried interface. For instance, a device manufacturer may opt to embed network variable names in a device to make certain that the queried network interface includes these names.
Following are the benefits to using device interface files:
- A device interface file may contain information that is not available in a device such as network variable names.
- Besides, a device interface file can be employed during network engineering when the device is not accessible from the network engineering tool.
Device Interface file formats
The primary device interface file type is a text file with a .xif extension. For performance optimization some platforms such as the LNS network operating system are used to convert this file to alternate formats, like LNS uses
- a binary device interface file (.xfb extension) and
- an optimized device interface file (.xfo extension).
Both of these files are created from the data contained within the text device interface file. The XIF32BIN Device Interface File Conversion Utility is used to convert a text device interface file to a binary device inteface file. The optimized device interface file is created automatically by LNS to diminish the access time to data within a device interfae file. Other network operating systems can create their own optimized versions of the device interface file. Device interface files are usually generated by LONWORKS development tools. Many of the fields of the device interface file for a device must match the application in the device. If the modifications done in a device interface file do not match the application it is documenting, installation errors may arise for the device.
Text Device Interface File Format
A text device interface file includes following four sections:
- Header: It is the first section of the device interface file, and is a mandatory section. All other sections are optional, except for the header section. This section depicts some basic information about the capabilities of the device, such as the transceiver type and buffer configuration.
- Network variable and message tag definitions: This section normally consists of zero or more network variable or message tag definitions.
- File definitions: This section includes the configuration files utilized for defining configuration properties implemented within configuration files. These files include zero or one template file definitions followed by zero, one, or two value file definitions. This section was added in version 4.0 device interface files and was not available earlier.
- Network variable value definitions: This section illustrates default values for configuration properties implemented as configuration network variables. This section was also added for version 4.0 device interface files only and is not present in version 3.1 and earlier files.