Specifications

46 RSLinx – Training Guide
Lab/Discussion: DDE Terminology
You should be familiar with the following terms (if not, please read the immediately
preceding pages titled DDE and how it works).
• Clients
• Servers
• Client/Servers
Three Basic Parts to any DDE request:
• Application
• Topic
• Item
Examples RSLinx Excel
Application RSLinx Excel
Topic Testsol
(a PLC station)
[book1.xls]sheet1
(an Excel spreadsheet)
Item T4:0.acc
(a valid PLC data table address)
R2C3
(a cell address)
Types of Links:
Hot Link A hot link is a DDE channel that remains open, though it is
only updated when the server sees a data change.
Cold Link A cold link is only opened upon command, such as via an
Excel macro, or some other program implementing a DDE
communication.
Types of links to RSLinx:
Bit/Word Read Hot link or Cold link with a macro
Block Word Read Hot link or Cold link with a macro
Bit/Word Write Cold link with macro only
Block Word Write Cold link with macro only