Specifications

RSLinx – Training Guide 41
Training Section 5: DDE and How It Works
Dynamic Data Exchange (DDE) is an interprocess
communications specification that is built into the
Microsoft Windows operating system.
It allows Windows programs that support DDE to
exchange data between themselves. All
communications occur within the Windows environment, essentially transparent to the
users, using very simple communication instructions.
The easiest way to visualize Dynamic Data Exchange is to think of a conversation
between people in a room. These people represent the different Microsoft Windows
applications (software programs) running on your computer.
Some of the people in the room ask questions (clients), others provide answers
(servers), and some both ask questions and provide answers (client/servers).
• In other words, the client initiates or requests a data transfer and the servers
respond to the request by providing or accepting data.
Dynamic Data Exchange questions are quite generic. When Microsoft Excel asks
RSLinx a question, it is merely looking for data. Excel does not know where the data is
coming from. Excel only knows that it asked RSLinx a question, and if RSLinx has an
answer, then the data will be provided.
Note: Not all applications that run under Microsoft Windows support DDE.
Check with an application’s manufacturer before purchasing an
application for use with RSLinx.
RSLinx
Microsoft
Excel
Note: AdvanceDDE protocol is the
only version supported by
RSLinx-OEM. DDE is not
available with RSLinx Lite.