Remote Devices

Note: Individual remote device EIE configurations are typically referred to in the CygNet Help as "remote devices," which reflects how they are displayed in the remote device editors in the Device Definition Service (DDS).

CygNet does not produce remote terminal unit (RTU) nor programmable logic controller (PLC) devices, nor does it produce any of the numerous physical communication devices used in the field. Instead, CygNet develops (among other things) the software tools to enable these physical devices to interface with CygNet services. The primary tool CygNet has developed for interfacing with field devices is the equipment interface engine (EIE).

An EIE type corresponds to the interface of a specific field device type. Be sure to select a communication device EIE component when configuring a remote device EIE. Since the communication device EIE is a separate component from the remote device EIE, in most cases any communication device EIE may be paired with any remote device EIE.

Note: The OPC remote device EIE can only be paired with the OPC Comm device.

There are three basic types of remote device EIEs:

Native or Proprietary Protocol: Uses a proprietary communication protocol typically developed by the hardware (physical/field device) manufacturer. Native protocols can be very efficient for handling specific features provided by the field device and often require very little configuration at install.

Modbus-Based Protocol: Supports connectivity to a variety of Modbus-capable devices. The Modbus EIE supports the Modbus RTU protocol as well as other extensions, including single- and multi-register read/writes of 32 bit integer/floating point and string values. A Modbus EFM EIE is provided as an interface to any field device that follows the Modbus RTU standard. Modbus RTU, TCP, and ASCII protocols are supported. Additionally, device-specific EIEs are available that are based on the underlying Modbus protocol but contain added functionality to take advantage of unique capabilities of particular field devices.

Application Programming Interface (API): Some device manufacturers choose not to document or expose the byte-level protocol used to communicate with their field devices. In such cases, the manufacturer usually supplies a .dll file with an API to the field device.

EIEs are housed and accessed in the Device Definition Service (DDS), which is also the repository for field device data. While the 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 a limiting factor. Each instance of a remote device is a facility; it can be assigned additional descriptive attributes in the Facility Service (FAC).

The following topics describe the ways CygNet interoperates with supported field devices. If you are interested in which field devices are supported by which EIE, see Supported Field Devices.