Device Template Files

Note: Technical details about field devices (RTUs, PLCs, modems, routers, and so forth) mentioned in this document are limited to only what is necessary to successfully use CygNet services to interoperate with them. It is assumed that you are familiar with your field devices. It is also assumed that you have access to field device technical documentation and/or support through the field device manufacturer.

A device template file (.dtf) is an .xml file that defines the data structures, communication tasks, and characteristics of a remote device EIE within the CygNet structure. It acts as a special interface with a remote device EIE, giving you customizable and fine-tuned control over a remote device EIE without the need for much custom coding. The recommended file extension for a device template file is .dtf, which allows the device template files to be readily identified. However, the .xml extension is also allowed. A device template file can be created with any text or .xml editor.

Use of a device template file not only reduces the need for much custom code, but it also enables you to satisfy new remote device requirements relatively easily. In many cases, data groups and data group elements can be added, deleted, or otherwise altered, as can communication tasks and conditions. And these alterations can then be pushed out to numerous remote devices serving numerous field devices.

CygNet device template files take advantage of a one-to-many relationship between the device template file and the remote device configurations in a Device Definition Service (DDS). Use each device template file to serve multiple instances of the same or similarly configured remote devices. In cases where alterations must be made to a subset of remote device configurations that use the same device template file, those changes can often be made on an ad hoc basis within the remote device editor. The remote device editor also enables all remote device configuration above and beyond the base interface between a field device and a CygNet remote device engine. For instance, while a device template file defines the data group elements and structures that allow CygNet to "speak" to a field device, the remote device editor allows the data received from the field devices to be organized, stored, tagged for different purposes, and so forth.

Device template files vary by remote device type and sometimes by field device models within an EIE type. Some device template files are very rigid and closely reflect a field device manufacturer's protocol. Other device template files are relatively free-form and follow industry-wide protocols, like Modbus. Each reflects the content and structure of the protocol or field device type it serves. But there are significant commonalities between all CygNet device template files. They all share similar template-level structural rules and most device template files use the same elements most of the time. (For exceptions, see remote device-specific documentation.) Elements are the building blocks of a device template file; as with any .xml file, they must follow standard, hierarchical rules of assembly. CygNet provides template validation tools to help ensure that you can have well-formed and valid device template files. Sample device template files are available upon request for most of the remote device EIEs CygNet develops.