Omron NY532-5400 Reference Manual page 1441

Additional Information
Operation of _**_Active System-defined Variable
• When this instruction is executed, the _**_Active system-defined variable for the specified event task
will change to TRUE. It will change to FALSE when execution of the event task is completed. For
example, assume that the execution priority of event task T2 is lower than the execution priority of
periodic task T1. When the ActEventTask instruction is executed for T2 in T1, the system-defined
variable _T2_Active will change as shown in the following figure.
Execution priority
Periodic
High
task T1
Event
task T2
Low
TRUE
_T2_Active
FALSE
• The event task will not be executed even if this instruction is executed while the system-defined vari-
able _**_Active for the event task is TRUE.
Execution priority
Periodic
High
task T1
Event
Low
task T2
TRUE
_T2_Active
FALSE
Executing an Event Task Only Once and Executing It Repeatedly
Use the following type of programming when you want to execute an event task only once when the
value of a specified variable changes and when you want to execute an event task repeatedly as long
as the variable has a specific value.
Example 1: Executing an Event Task Only Once When the Value of a Specified Variable Changes
If you use an upward differentiation instruction option for the instruction as shown below, event task
'Task1' will be executed only once when the value of BOOL variable BoolVar changes from FALSE to
TRUE.
NY-series Instructions Reference Manual (W560)
Task period
Task period
ActEventTask('T2')
Task period
Task period
ActEventTask('T2')
ActEventTask('T2')
ActEventTask('T2')
The event task is not executed.
2 Instruction Descriptions
Execution of task processing
Pausing of task processing
Task period
Time
Execution of task processing
Pausing of task processing
Task period
Time
2
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