<4. Control Application Creation>
4.1.3 Multi-tasking
This section describes the considerations and precautions for running multiple tasks
concurrently on an FCN-500 or FCN-RTU.
SEE ALSO
For details on the behavior of the FCN-500 or FCN-RTU when multiple tasks are created, see Section
4.3.3, “Task Schedule” of TI “FCN-500 Technical Guide,” Section 4.3.3, “Task Schedule” of TI “FCN-
RTU Technical Guide.”
● Considerations Multi-tasking
Two possible reasons for considering implementing multi-tasking are given below:
1. To create control tasks having different execution intervals in an attempt to
reduce CPU load of the FCN-500 or FCN-RTU. For details, see Section
2.2.4, “Determining FCN-500, FCN-RTU Scan Cycle.”
2. To create control tasks having the same execution interval and priority
level for sorting control tasks to be instantiated by function.
The FCN/FCJ runs without problems even with multi-tasking. However, in multi-
tasking mode, tasks are processed alternately at intervals of 30 ms in a time-sharing
manner as described in TI “STARDOM Technical Guide” and this complicates desk
investigation of control applications.
Therefore, running one task per FCN-500 or FCN-RTU is generally recommended.
When deciding on control application execution, start with single-tasking and
consider multi-tasking only if it is necessary.
Even when considering creating multiple tasks so as to reduce the CPU load of the
FCN-500 or FCN-RTU, listed as the first reason above, first consider the option of
lengthening the execution interval of a single control task, and consider multi-tasking
only if the first option is disallowed by the requirement specification.
Creating multiple tasks having the same execution interval and priority for sorting
purpose, listed as the second reason above, is unnecessary.
Multi-tasking not only complicates system operation, it may also increase CPU load
due to processing for sharing such as shared access to I/O modules.
For these reasons, it is best to avoid splitting a single task into multiple tasks having
the same execution interval and priority.
● Precautions When Multi-tasking
Pay attention to some precautions when using multi-tasking.
SEE ALSO
For details on precautions when multi-tasking, see Section 8.3, “Precautions about Multi-tasking" of
Chapter 8, “Detailed Description."
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