Product : ISaGRAF V3.32

Date : 10-August-1999

File : Debug.Spying problem with pulse signals.htm

Subject : Spying problem with pulse signals

Keywords: Spy - Debug - pulse - Spotlight


When spying variables with the ISaGRAF debugger, the debugger

chains at least 3 different requests sent to the target:

- Get state of the PLC

- Get list of warning messages

- Get values of spied data

The ISaGRAF target running in REAL TIME mode

(this is also the case for the Simulator) can answer at only one

request per cycle.

This implies that you cannot see with the debugger

states from the same variables on three consecutive cycles.

This is particularly visible in SpotLight curves:

if you register on a curve a pulse signal(with a change during just

one cycle) you may not see its change on the curve.

=> If you need to check such volatile signals with the debugger,

please run the application in CYCLE TO CYCLE mode.

This problem does not occur in this mode.

Run application DBCYCLES to understand better.

This is a simple cyclic program making "counter := counter + 1".

The application is set with a cycle timing of 500 ms so you have

time to see...

Run the application in the simulator and view "counter" variable.

You can see that its displayed value increases with "3" step.


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