Product: ISaGRAF V3
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,
- The debugger asks for a set of variable values on each "cyclic
refresh" period. This duration can be set up from the debugger
- 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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