Chapter 5 Program Configuration and Operation Method
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(2) Execution priority
y
In case that several tasks to be executed are waiting, execute from the highest Task Program in
priority. When the same priority tasks are waiting, execute from the order occurred.
y
Task priority relates to each task.
y
The task program priority should be set considering the program features, importance and the
emergency when the execution requested.
(3) Processing delay time
There are some causes for Task Program processing delay as below. Please consider this when task
setting or program preparation.
y
Task detection delay (Refer to detailed description of each task.)
y
Program proceeding delay caused by Priority Task Program proceeding
(4) Relationship of initialize, Scan Program and Task Program
y
User identification task does not start while performing Initialization Task Program.
y
As Scan Program is set as lowest priority, if task occurs, stop Scan Program and process Task
Program in advance. Accordingly, if task occurs frequently during 1 scan or concentrates
intermittently, scan time may extend abnormally. Cares should be taken in case of task condition
setting.
(5) Protection of Program in execution from Task Program
y
In case that the continuity of program execution is interrupted by high priority Task Program during
program execution, it is available to prohibit the execution of Task Program partially for the part in
problem. In this case, it is available to perform the program protection by ‘ DI(Task Program Start
Disabled) and ‘EI(Task Program Start Enabled)’ application instruction.
y
Insert ‘DI’ application instruction in the start position of the part requiring the protection and insert ‘EI’
application instruction in the position to release. Initialization Task is not influenced by ‘DI’, ‘EI’
application instruction.
4) Time Driven Task Program Processing Method
Here describes the processing method in case that task (start condition) of Task Program is set as Time-
driven.
(1) Items to be set in Task
y
Set the execution cycle and priority which are the start condition of Task Program to execute. Check
the task no. to manage the task.
(2) Time-driven Task Processing
y
Performs the corresponding Time-driven task program per setting time interval (execution cycle).
Notes
1) For further information of interrupt program, please refer to 5.2.3 Interrupt.
