Chapter 5. Program Configuration and Operation Method
5-6
(1) Scan program
(a) Function
• This program performs the operation repeatedly from 0 step to last step in order prepared by the program to
process the signal that is repeatedly regularly every scan.
• In case that the execution condition of interrupt by task interrupt or external input while executing program is
established, stop the current program in execution and perform the related interrupt program.
(2) Interrupt program
(a) Function
• This program stops the operation of scan program and then processes the related function in prior to process
the internal/external signal occurred periodically/non-periodically.
(b) Type
• Task program is divided as below.
- Cycle time task program: available to use up to 8.
- Internal device task program: available to use up to 8.
- I/O (External contact task program): available to use up to 8. (%IX0.0.0~%IX0.0.7)
• Cycle time task program
- Performs the program according to the fixed time internal.
• Internal device task program
- Performs the corresponding program when the start condition of internal device occurs.
- The start condition detection of device shall be performed after processing of scan program.
• I/O (External contact task program)
- Performs the program according to the input external signal (%IX0.0.0~%IX0.0.7).
(1) Write the interrupt program as shortly as possible. In case same interrupt occurs repeatedly
before completion of interrupt, program is not executed and O/S watch dog error may occur.
(2) Though interrupt which has lower priority occurs many times during execution of interrupt
which has higher priority, interrupt which has lower priority occurs only one time.
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