In serial communications, speed and convenience are the two most important points. For real-world applications, there are numerous serial devices in the industrial environment that need to connect to various hosts for control. Early systems used dedicated copper lines to connect these serial devices and vendor-specific proprietary serial protocols for industrial applications. While adequate for many applications, a one-cable, one-device system presents issues of limited transmission distance, limited hardware resources and limited interface options of each serial device.

Recently, the advent of Ethernet has made it possible to solve the distance and interface limitations of serial devices. Ethernet is a ubiquitous solution that has established itself as the principal industrial network through a combination of high data rate and shelf infrastructure.

Based on the trend of Ethernet, serial device servers are designed to network-enable any device using the RS-232 or RS-422/485 serial communication protocol. By encapsulating serial data and transporting it over Ethernet, the serial device servers allow virtual serial links over Ethernet and IP (TCP/IP, UDP/IP) networks. After COM redirection software installation, standard serial operation calls are transparently redirected to the serial device servers, guaranteeing compatibility with legacy serial devices and enabling backwards compatibility with existing software. As a result, you can extend the distance of the serial connections within the plant, throughout the factory, the facility, the office building, or across a global enterprise.

The ARC report estimates that by 2011 the market opportunities for industrial Ethernet will exceed US $900 Million. This means that almost any communication device in the world can be part of this booming market, if it has the right interface. The interface of the serial devices should be transformed to keep up with Ethernet trends.

Source: ARC Advisory Group
To take advantage of this tremendous market opportunity, industrial devices need to be developed more customer-oriented. Additionally, the immediate benefits of Ethernet-enabled serial device servers include:
* Efficient Communications - Instead of having one device communicating with one computer, one device can communicate with every computer on a network.
* Lower Cost of Ownership - Some serial devices already have the proper interface for Ethernet communications. There is no need to upgrade an existing serial device to newer, costlier version just to have a built-in Ethernet interface.
* Extended Life of Software - Many existing software can be used to communicate with the serial device as if connected to a local COM port.

Although serial device servers offer an easier way to network RS-232, RS-422/485 serial devices, there are still some limitations about current serial device servers. Using a serial device server, the device can communicate to only one computer on network in a set period of time. The data from the device is transferred to this computer only. No others can share this data. Most serial device servers provide only one LAN port. If this connection fails, the device can not connect to the host anymore. Some serial device servers provide two LAN ports and only support the cascading connection (Daisy Chain). It's better than the only one LAN port module, but if one of the connections fails, the modules behind this path will lose connection.

Considering the pros and cons of serial device connections and the rising advent of Ethernet, Advantech's EKI RS-232/422/485 serial device servers combine rugged, compact and fast 1 or 2 RS-232/422/485 serial ports with 2 LAN ports and 2 power inputs for redundant networking. With this advanced technology, EKI serial device servers have two powerful features to ensure transmission stability; "Simultaneous Dual-LAN Redundancy", and "Advanced Multi-Access Functionality".

Simultaneous Dual-LAN Redundancy
With redundant LAN connections, communication is not interrupted in the event of a network problem. With one connection automatically assigned as the primary andthe other as a backup, the loss of the primary connection initiates an immediate and automatic switch-over, ensuring data integrity and peace of mind.

Advanced Multi-Access Functionality
Instead of the unique one cable-one device system required by RS-485 Modbus systems, Ethernet permits the use of servers and gateways through which serial data is transported over an Ethernet network to the recipient host. Advantech provides powerful Serial-to-Ethernet, Ethernet-to-Serial serial device servers. EKI Serial Device Servers combine various operations; such as COM port redirection, TCP server/client and UDP mode to fulfill advanced needs.

EKI-1000 series also supports Multi-Access functionality to provide 5 host connections for each serial port with broadcast and polling operations. In broadcast mode, EKI Serial Device Servers handle a command from one application and reply to the data from the serial port to all applications connected to this serial port. In polling mode EKI Serial Device Servers handle the commands from one application and reply to this application only. Query from other applications must be queued and wait for current process completion.

Below is a list of a few key Advantech Serial Device Servers:

Through Dual-LAN redundant connections, EKI Serial Device Servers greatly improve connectivity, reliability, system stability, and simplify redundant configurations, regardless of whether the devices are in the same domain or not. And by using Serial Device Servers to share serial devices, users can eliminate separate serial lines and serial devices attached to individual hosts. Collecting the data from these serial devices is easier and more effective.

Courtesy of Advantech