YOKOGAWA STARDOM FCN-500, Engineering Manual

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<4. Control Application Creation>
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TI 34P02K35-02E Jun. 6, 2018-00
4.1.2 Control Task Setup
Control applications created in Logic Designer are created by assigning to tasks and
turn into instances. This section describes task types and task settings.
● General Limitations of Control Tasks
All control tasks are subject to the following limitations.
• Limit on number of tasks
Up to 16 control tasks can be created for one FCN-500 or FCN-RTU. Running
only one control task on one FCN-500 or FCN-RTU is known as single-tasking,
while creating and running multiple control tasks concurrently on one FCN-500
or FCN-RTU is called multi-tasking.
• Task name
A task name consists of up to 7 alphanumeric and underscore (‘_’) characters
with the following restrictions:
- A task name cannot begin with a number.
- A task name cannot contain two contiguous underscore (‘_’) characters.
- A task name cannot end with an underscore (‘_’) character.
● Types of Control Tasks
There are three types of control tasks with different behaviors.
• Cyclic
A cyclic task is run at a specified interval, known as scan cycle. This task type is
used for most control applications.
• Default
A default task has the lowest execution priority among all control tasks. It is not
executed at fixed intervals. Instead, it is executed automatically when all other
control tasks are idle (not executing).
A default task is executed at variable execution intervals as its execution is
dependant on the operation of other control tasks. Hence, this task type is, in
general, not used in control applications.
• System
A system task is run when there is a change in the operating status of the FCN-
500 or FCN-RTU, or when an error is detected in the FCN-500 or FCN-RTU.