User Manual

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Cellular Networks
Although it allows different equipment from different vendors to communicate with each other, it does
not utilize the bi-directional and “push” technology advantages of Ethernet networks. For example, if an
intelligent device wanted to send alarms and execute front-end logic, it could take advantage of Ethernet
network communication technology used in IT. The vast majority of markets have accepted Ethernet
networks for their HMI/SCADA systems.
What does the future have in store? Experts foresee the next generation of SCADA to be a mix-and-match
system that takes advantage of XML, web service, push, and other modern web technologies.
New Push Technology from Moxa Active OPC Server
Active OPC Server Lite is a software package provided by Moxa that operates as an OPC driver for an HMI
or SCADA system. It offers seamless connection from Moxa’s ioLogik series products to SCADA systems,
including Wonderware, Citect, and iFix. Active OPC Server Lite meets the latest standard of OPC DA 3.0,
which allows connections to various kinds of devices and host OPC machines.
Communication from I/O to SCADA
There are many kinds of communication methods between SCADA/HMI software and remote devices, such
as I/O devices, RTUs, or PLCs. In the past, proprietary protocols were provided by device manufacturers who
always supplied drivers to make their devices compatible with SCADA/HMI software or provided their own
SCADA software. Today, Modbus protocol is quickly becoming the standard among hardware manufacturers
with SCADA/HMI software vendors also jumping on the wagon. Although Modbus offers compatibility
between most devices and SCADA software, not all devices support Modbus protocol. Achieving a standard
mechanism for communicating with numerous data sources, such as devices on the factory floor or a database
in a control room, is the motivation for the development of OPC. SNMP protocol is used in IT to manage
various Ethernet devices, and OPC Client/Server architecture supports SNMP. Moxa’s innovative Active
Ethernet I/O products support Modbus/TCP, OPC Client/Server, and SNMP for greater flexibility compared to
passive remote I/O.
Passive I/O Active Ethernet I/O RTU PLC
Proprietary Protocol No No No Yes
Modbus/TCP Yes Yes Yes Yes
SNMP No Yes No No
OPC Client/Server (Polling) No Yes No Needs driver
OPC Client/Server (Push) No Yes No No