User Manual

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2009 Industrial Wireless Guidebook
Cellular Networks
3
General OPC servers typically use the “poll/response,” or so-called “pull” architecture, to connect to Ethernet
I/O devices, which involves an HMI/SCADA system continuously sending out commands to collect relevant
data. Moxa’s Active OPC Server, with its non-polling architecture, supports the standard OPC protocol, but
also offers active (or “push”) communication with Moxa’s ioLogik series of Active Ethernet I/O products to HMI/
SCADA systems, providing instant I/O status reports.
I/O Response that’s 7 Times Faster and Provides 80% off Bandwidth Usage with Event-driven Tag
Updates
Adding additional I/O channels will tend to bog
down an HMI/SCADA system’s operation, resulting
in a longer response time , and high network
bandwidth occupation, all because of the traditional
“pull” architecture. Active tags created by Active
OPC Server Lite and ioLogik series products report
the I/O status only when it changes.This type of
event-driven tag status update results in an I/O
response time that is 7 times faster than other OPC
Server packages (using a testing environment with
2,560 I/O channels). In a different test of network
bandwidth usage, Active OPC Server Lite and
the ioLogik caused an apparent 80% reduction in
network traffic. The end result is that I/O access is
more precise, and the cost of communicating with
remote I/O devices is substantially lower, especially
when the remote site has limited bandwidth (e.g.,
satellite, microwave, and cellular communication).
At the same time, the CPU usage of the SCADA/
HMI system is also reduced by 35% with this
innovative push-based architecture, so that less
maintenance effort and lower level hardware
devices can be implemented.
General OPC Server
Polls continuously
Local Network and Fixed IP
Connection only
Internet and Dynamic IP
Connection
Router
Remote I/O
ioLogic
Active OPC Server
No polling required
Pull-based OPC Server
Push-based Active
OPC Server