Automation Media
is dedicated to develop the awareness and understanding about interoperability in automation
by providing best information from best sources about
open specifications that standardize the communication of acquired process data,
alarm and event records, historical data, and batch data to multi-vendor
enterprise systems and between production devices. Production devices include
sensors, instruments, PLCs, RTUs, DCSs, HMIs, historians, trending subsystems,
alarm subsystems, and more as used in the process industry, manufacturing, and
in acquiring and transporting oil, gas, and minerals.
OPC Foundation
owns all OPC trademarks including the OPC logo used throughout this site. Most of information in
OPC Knowledge Base is from OPC foundation.
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Welcome to the Automation Media's OPC - OLE (Object Linking and Embedding) for Process Control
OPC Knowledge Base
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DDE - What is it?
OLE’s predecessor, Dynamic Data Exchange, is a method of dynamically moving data among applications in the Microsoft Win32 Application Programming Interface (API).
The DDE protocols send messages between applications that share data and use shared memory to exchange data.
Applications can use the DDE protocol for one-time data transfer and for continuous exchanges in which applications send updates to one another as new data become available.
Prior to OPC, hardware manufacturers that recognized the need for software connectivity to their hardware was limited in their ability to develop drivers—the choice was between DDE and a list of proprietary DDE derivatives. Selecting any of these had possible
effects of limiting the user’s choice of software or preventing the acceptance of the hardware.
Due to OPC data exchange popularity, DDE is becoming less popular.
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