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Chicago-At National Manufacturing Week in March, Adlink Technology (Irvine, CA) introduced a simple yet elegant network interface called the High Speed Link (HSL). It uses the economical and pragmatic approach of clustered I/O (inputs and outputs) to solve what has become the most prevalent problem in PC-based control-that is the enormous wiring problem back to all the backplane cards in the PC.
HSL is a fast serial interface that uses a PCI-based master card plugged into an industrial computer. A single CAT5 cable connection links all terminal blocks, slave I/O modules, and provides shielding. HSL can achieve real-time control of up to 2,016 I/O per master card, or 32,256 real-time I/O from 8 PCI-7852 dual master, four port controller cards.
Using a single CAT5 cable daisy chained from one I/O slave module to the next, HSL (a new RS422-based network interface) tackles the enormous problem of wiring all of the I/O back to the PC.
"One port of the HSL Master can connect up to 1,024 I/O for process control and/or sensing, transmitting data at 6Mbps with refresh rates every 30.1 micro seconds for a single slave module," says Steven Neo, director of Adlink's U.S. office, "all in real-time, directly from the devices to the PC and other workstation environments."
Implementation consists of a single HSL master with two ports or a dual master with four ports that plug into a single PCI-bus slot of any PCI-based chassis, cPCI (CompactPCI), or workstation. One port of the master can drive a maximum of 32 slave I/O modules and 31 modules on the other port making for a total 63 slave modules per master. "Each slave module can network up to 32 I/O points, regardless of their type," says Neo. "And all data is constantly processed through the HSL master without loading the PC's CPU."
Distributed I/O slave modules can be daisy chained back to the PC using standard CAT5 cable or arranged in a 'star' topology with hub-like connectors.
"Wiring and maintenance is much simpler using HSL technology," explains Neo, "because HSL eliminates the miles of cable runs typically required from the location of the sensors or controllers to the host. Instead, HSL uses a single CAT5 cable daisy chained from one I/O slave module to the next. The ability to distribute the slave modules close to the I/O makes active cable runs shorter, and reduces the potential of noise interference and signal loss." The maximum length of a single HSL run can be up to 200 meters; however, repeaters can extend the distance even further.
HSL supports popular OS and RTOS, easing integration of applications such as motion control or vision. In addition, it's easily programmed using third-party IEC 1131-3 compliant software standards, such as ISaGraf, that include softPLC, sequential function chart, function block diagram, ladder diagram, structured text, and instruction list.
Combined with the use of IPCs and cPCI, HSL technology creates an open architecture platform and upward migration compared to the PLC's costly and logistically difficult alternative. HSL technology benefits include easier upgrades and integration of new software and hardware such as motion and vision add-on cards, additional I/Os, and independence from PLCs. However, HSL appears to run counter to the trends in the industry toward proliferating networking standards such as Ethernet, and more specifically TCP/IP over Ethernet.
While the number of I/O that can be handled on a single PC using HSL is impressive, industrial networks based on commercial technologies take advantage of inherent rapid pace of change and lower costs to provide certain strategic advantages for many applications. Though, there are certainly going to be exceptions where performance criteria dictate a certain technology, such as HSL's deterministic PC-based control of a large number of I/O points, these will probably be the exceptions rather than the rule in the end.
Adlink has formulated an open-control platform that gives engineers many choices in the software domain. However, it will be restrictive in terms of I/O selection because today, no I/O device on the market is HSL compatible. Therefore, customers are highly dependent upon Adlink's I/O offerings. And, if ADLINK really wants to broaden its market penetration, the company will have to roll out more I/O.
Contact Steven Neo, Adlink Technology Inc., 17951 Sky Park Circle, Irvine, CA 92614; Tel: (949) 250-3339; Fax: (949) 250-3336; E-mail: [email protected], or Enter 505