Tuesday, April 10, 2001
Chicago--If you've got miles of wire in your centralized
PC-based control application, you might find a new serial network interface
called HSL (High Speed Link) interesting. Adlink Technology Inc. (www.adlinktechnology.com) introduced
the RS422-based network last month at National Manufacturing Week. Using
clustered I/O, standard RJ45 connectors, and CAT5 cable, HSL tackles PC-based
wiring and maintenance issues.
Targeted at real-time, deterministic applications, HSL consists of
single or dual PCI-based master cards that have two or four RJ45-ports
respectively. A master card plugs into a single PCI-bus slot of any PCI-based
chassis, cPCI (CompactPCI), or workstation. And standard CAT5 cable links all
terminal blocks and slave I/O modules to achieve real-time control of up to
2,016 I/O per master card, or 32,256 real time I/O from eight PCI-7852 dual
master, four-port controller cards in a single PC.
"One HSL Master port handles 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," explains Steven Neo, director of Adlink's
U.S. office. "So engineers just have to multiply the number of slave modules by
30.1 micro seconds to determine the polling cycle time." One port of the master
can drive a maximum of 32 slave I/O modules and 31 modules on the other port
making for 63 total slave modules per master.
Using CAT5 cable daisy chained from one slave module to the next,
or arranged in a "star" topology with hub-like connectors distributes the I/O in
order to reduce the length of active cable runs, and decrease the risk of noise
interference and signal loss. Other 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.
While Adlink has formulated an open-control platform that gives
engineers many choices in the software domain, at least initially it will be
restrictive in terms of I/O selection. Why? Because today, only Adlink's I/O
offerings are HSL compatible. Moreover, HSL appears to run counter to the trends
in the industry toward proliferating networking standards such as Ethernet.
Nonetheless, there are always exceptions where performance
criteria dictate a certain technology, such as HSL's real-time control in high
I/O-count applications. But to keep from being the exception rather than the
rule, Adlink will have to roll out more I/O to broaden its market penetration.
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