Task Pool and Task Manager
If we now think of our routines as POU’s written for each function and given names, we can cre
-
ate a Task for each of our assigned POU’s.
Each Task can have different operating conditions, or events.
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Task #1 only runs when a tag named, ‘Man_On’ is true.
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Task #2 only runs when a tag, named, ‘Auto_On’ is true.
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Task #3 runs all the time (event = True denotes this)
These tag names would be declared as Global Variables and assigned to PLC bit devices (they
could be addresses i.e. X0).
Consider our original control program. Conditional Jump (CJ) instructions could be used to iso-
late, either routines #1 or #2, when not in use. The Heating control routine is always required to
run.
If these routines are considered as tasks, then routines #1 & #2, are driven by event, i.e. when
either auto or manual is selected, whereas, routine #3 is always on.
Programming Software Structure and Definition of Terms
Training Manual GX IEC Developer 3 - 7
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