Echelon LNS DDE Server - Manual (Page 81)

1 In the LNS DDE Server folder pane, navigate from the top level down
through the hierarchy to the network variable level.
2 Right-click the network variable that you want to monitor, and choose
Copy Link from the shortcut menu.
3 In InTouch WindowMaker, click the Wizards icon on the toolbar. Select
I/O Analog Display from the Value Displays category, and click OK.
4 Place the object on the window and then double-click it. Select Paste
Link In in the dialog and then click OK.
5 InTouch will now try to provide a tag-name based on the item. A dialog
will inform you about it if it succeeds. Click OK to close the dialog and
then either change the tag-name or click OK to use the tag-name
provided by InTouch.
Now InTouch will receive ongoing updates from the LNS DDE Server.
Sending a Network Variable Update
To change a network variable's value, your application sends a DDE poke message to
the LNS DDE Server. The LNS DDE Server does not need to be bound to a variable
to be able to change its value. How the LNS DDE Server processes the poke
command depends on the direction of the variable.
If the network variable on the device is an input, the LNS DDE Server updates the
variable on the device. If the input network variable is part of a connection that
includes other input network variables, only the network variable specified in the
item is affected. Outputs connected to the variable are not changed. Another device
polling this variable will receive the new value.
If the network variable is an output on a device other than the host PC it cannot be
updated.
If the network variable is an output on the LNS DDE Server host PC, all input
network variables connected to the output network variable are updated
Input network variables on the LNS DDE Server host cannot be updated.
If you are sharing the network interface with another application, it is possible that
the interface will be busy when the LNS DDE Server attempts to send the update.
In this case, the LNS DDE Server will come back periodically and check to see if the
interface is free to send the update. If your DDE client application or another DDE
client application sends another update request for the same variable before the LNS
DDE Server has sent the previous update, only the most recent update will be sent.
Note: If you are updating multiple fields of a network variable structure, you should
set the DDE_WriteDelay point property before writing to the first field (see Point
Properties in Chapter 8). This property sets a millisecond timer which begins
counting down when a network variable value is updated using the LNS DDE
Server. The new value will not be sent to the device until the timer expires. After the
LNS DDE Server User's Guide 5-11