Devices Overview
CygNet Software provides a variety of device Equipment Interface Engines (EIEs) to perform interface functions between a large number of available field devices and your CygNet system.
Equipment Interface Engines
Each field device type that can be added to a CygNet system (Communication devices, Remote devices, and Import/Export devices) uses a corresponding type of equipment interface engine (EIE) to work with CygNet Software. An EIE can be viewed as a plug-in module for a CygNet host computer that enables the CygNet host to "speak" the language or protocol of the field device.
See the following sections for more information about specific EIE types.
EIE Functions
EIEs are responsible for the following functions.
- Handling device-configuration tasks
- Constructing and interpreting communication messages
- Storing received data
- Providing dialog boxes for user editing of data
- Maintaining trace data for analysis and troubleshooting
- Performing extended tasks for device-specific features
EIEs can be added, configured, and deleted at any time without impacting the availability or performance of a production system. Once added, any available network-connected workstation with proper authorization can perform all of the tasks required to operate and manage supported field devices.
There is no limit to the number of supported field devices that can be added to a CygNet host. But while the Device Definition Service (DDS) has no defined limit of remote devices it can support, limitations are imposed by host hardware, operating system, memory, and so forth. The 64-bit version of the Universal Interface Service (UIS) can support up to 5,000,000 points, so points per remote device is also a limiting factor. You can use the EIE to help you continually evaluate and select the best possible field devices for ongoing replacement efforts and new installations without the concern of overly complicating your SCADA system or jeopardizing its reliability.
EIE Components
The major components of a CygNet EIE are as follows.
Device Driver
Each type of field device supports one or more methods to communicate with host computers. These methods are built into the field device by the manufacturer and are defined by the electrical interface to the field device and its messaging protocol. An EIE "speaks" the communication protocol and the message structures of a field device, which allows information requests from a CygNet host to be translated into a poll request understood by a field device. Likewise, an EIE "understands" messages received from a field device and passes the data in a generic format to the host.
Device-Specific Database
Communication with field devices involves the transmission and storage of large amounts of data with many different types of data structures. Examples of data structures are field device configuration settings, electronic flow measurement (EFM) history records, pump-off control cards, field device polling history, and status poll records. The variety, complexity, and size of these data structures is unique for each type of EIE.
An EIE is pre-configured to create necessary data structures, greatly simplifying the installation process by removing any need for a user or system administrator to create or manage database structures. When a new field device is configured for use with CygNet, the EIE automatically creates the data structures necessary to store and retrieve all information associated with the field device. The database is made available to the EIE for message processing and is available to users for reports, viewing, and any other data exporting or processing needed.
For more information, see Data Storage for DBS-Based Services.
Device Template File
A device template file (.dtf) is an XML file that defines the data structures, communication tasks, and characteristics of a remote device within the CygNet structure. It acts as a special interface with a remote device, giving you customizable and fine-tuned control over a remote device without the need for much custom coding. It also enables you to satisfy new field 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 device instances serving numerous field devices.
Device template files vary by 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 more information, see Device Template Files.
Data Viewers and Editors
Each EIE includes an extensive set of dialog boxes, data viewers, and data editors. The device editor is a human-machine interface (HMI) accessed from the DDS within CygNet Explorer. Data viewers and editors match device types and are designed to present and enable modification of all of the features and data associated with a device.
Viewers and editors enable you to:
- Configure devices
- Send and retrieve data
- Map information to point tags for alarming, HMI display, and storage
- View current and historical data records
- Configure communication methods
Place EIE viewers and editors on HMI screens to facilitate viewing and managing field device information.
For more information, see CygNet Studio.
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