LS Industrial Systems XBC-DN10E, Руководство пользователя

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Chapter 5 Programming Concepts
XBC E-Type Main Unit 5-14 Ver. 1
8. Verification of task program
a. Is the task setting proper?
i. If task occurs frequently more than needed or several tasks occur in one scan,
scan time may lengthen or be irregular. If it is not possible to change the task
setting, verify maximum scan time.
b. Is the priority of the task set properly?
i. The low priority task program shall be delayed by the high priority task program,
which results in disabling the processing within the correct time and even task
collision may occur as the next task occurs in the state that the execution of
previous task is delayed. Consider the importance of task and execution time
when setting the priority.
c. Are task programs made as short as possible?
i. Long running task programs can cause long or irregular scan times or may lead
to the conflict of task programs. Make the task programs as short as possible.
ii. When attaching expansion special module, or using PUT or GET instructions,
program processing might be delayed.( More than 10ms task cycle is
recommended).
d. Is program protection for the high priority task needed during program execution?
i. If another task is called during the task program execution, complete the task
being executed and operate the standby tasks in the order of high priority. In
case that it is not allowed to insert other task in Scan Program, prevent the
insert partially by using ‘DI’ and ‘EI’ application instruction. The problem may
occur while processing the global variables used commonly with other program
or special or communication module.
9. Program configuration and processing example
The tasks and program are registered below.
Interrupt type Interrupt name Priority Task No. Program
Cycle time 10
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_cycle time 3 0 Program 1
Internal device Internal device_M00 5 16 Program 2
I/O I/O_P00 2 8 Program 3
a. Scan program name: “Scan Program”
b.
Execution time respective program: Scan program = 17
㎳
, Program 1 = 2
㎳
, Program
2= 7
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, Program 3 = 2
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