User`s guide

Introduction to PCIS-DDE • 3
1.2 DDE Conversation
Two Windows application wishing to exchange data must establish a
conversation. The client opens a channel to the server application by
specifying:
l Server Application Name
For PCIS-DDE server, the application name is PciDDE.
l Topic (Logical Device) Name
The DDE topic is a general classification of data within which multiple data
items may be "discussed" (exchanged) during the conversation. For PCIS-
DDE server, the topic might be a NuDAQ board name with its card number,
e.g. Pci7200#0. The topic is active whenever at least one conversation has
been established between the server’s logical device and the outside
world’s applications (client). The topic is de-active when the last
conversation to a topic has terminated.
l Items/Tagnames
Items are individual pieces of data that are passed between applications.
An item is active whenever any DDE conversation is referencing this item.
All the valid item names for PCIS-DDE server are mentioned in chapter 4 of
this manual. For example, the item name is “PDI” for client application (e.g.
InTouch) to get the digital input data of PCI-7200.Please refer to the related
chapter for the details.
The following statement is the DDE address convention for representing an
DDE conversation:
Application|Topic!Item
For example, to get the digital input data of PCI-7200 through PCIS-DDE
server, the conversation might be the following (assume the topic name is
defined as Pci7200#0):
PciDDE|Pci7200#0!PDI