Chapter 5 Program Configuration and Operation Method
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(3) Notice in using Time-driven Task Program
y
When Time-driven task program is in execution currently or waiting for execution, if the demand to
execute the same task program occurs, the new occurred task shall be disregarded.
y
Timer that makes a demand to execute Time-driven task program only while operation mode is
RUN mode, shall be added. The shutdown time shall be all disregarded.
y
When setting the execution cycle of Time-driven task program, consider the possibility that the
demand to execute several Time-driven task program at the same time occurs.
If 4 Time-driven task programs that the cycle is 2sec, 4sec, 10sec and 20sec are used, 4 demands of
execution per 20 seconds shall be occurred at the same time and scan time may extend
instantaneously.
5) Internal Device Task Program Processing Method
Here describes the processing method of Internal Device Task Program which extended the task (start
condition) of Task Program from contact point to device as execution range.
(1) Items to be set in Task
y
Set the execution condition and priority to the task being executed. Check the task no. for task
management.
(2) Internal Device Task Processing
y
After completing the scan program execution in CPU module, if the condition of device that
becomes the start condition of internal device task program is met, according to the priority, it shall
be executed.
(3) Precautions in using internal Device Task Program
y
Accordingly, even if the execution condition of internal device task program occurs in Scan Program
or Task Program (Time-driven), it shall not be executed immediately but executed at the time of
completion of Scan Program.
y
If the demand to execute Internal Device Task Program occurs, the execution condition shall be
examined at the time of completion of Scan Program. Accordingly, if the execution condition of
Internal Device Task occurs by Scan Program or Task Program (Time-driven) during ‘1 scan’ and
disappears, the task shall not be executed as it is not possible to detect the execution at the time of
examination of execution condition.
6) Task Processing at the Momentary power failure
y
When restarting the task as the momentary power failure time is long, disregard the task in standby and
the task issued during shutdown all and process only the task from the starting point.
y
In the shutdown state within 20ms, the task in standby before shutdown shall be executed, after
recovering the shutdown. The cyclic task and Interrupt task that occurred in double during shutdown,
shall be disregarded.
