DDE links

There are three types of DDE links:

A

hot

link is the type of a link in which the server updates the client whenever the server sees the data change. Once established, this type of link remains intact until it is shut down. The Copy to Clipboard feature of RSLinx Classic can be used to quickly establish hot links to applications that support a Paste Link.

With a

warm

link, the server monitors the data, and when the data changes, the server sends a signal to the client telling the client that the data has changed, but the server does not send the actual data itself. At this point the client has the option of asking for the data or doing nothing. RSLinx Classic does not currently support warm links.

A

cold

link is established upon a request for data. Once the request is filled the link is broken. The next time data is required a link from the client to the server must be re-established. For example, a Microsoft Excel macro can be used to establish a cold link. All DDE writes are done through cold links.

Until a request for data is made from an application program, such as Microsoft Excel, RSLinx Classic waits for an application to make a request for some data from a processor. Once a request for data is made RSLinx Classic builds up the required communication packet to acquire the data and begins communication.