Product: ISaGRAF V3

Date: 22-July-1998

File: DDE.speed up the DDE exchanges for booleans.htm

Subject: How to speed up DDE Exchanges

Keywords: DDE - Debugger


Exchanging a lot of boolean variables through DDE between the

ISaGRAF debugger and an external application may lead to poor


Below are some explanations about debugger spying mechanism:

- The ISaGRAF debugger only spies variables required by connected

client. A debugger client can be the DDE link, or any other

ISaGRAF window used in debug mode (spy list, trace variables,

spy program...)

- The debugger asks for a set of variable values on each "cyclic

refresh" period. This duration can be set up from the debugger

'options' menu.

- The default cyclic refresh period is 500ms when debugger is used

in real connected mode. The default value is 100ms when debugger

is used in simulation mode.

- This period cannot be less than 10 ms.

- A set of refreshed variables (one exchange on the communication

link) groups at most 50 variables. For example, if the debugger

needs to refresh 200 different variables, it will take 4 times

the cyclic refresh period.


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