Mitsubishi Electric Q01UCPU User Manual page 87

(f) Interrupt during END processing
When the constant scan function is used and an interrupt factor occurs during the waiting time in END
processing, an interrupt program corresponding to the interrupt factor is executed.
(g) When an interrupt factor occurs during access to another module
When an interrupt factor occurs during access to another module (during service processing or instruction
processing), the interrupt program becomes standby status until the service processing or the instruction in
execution is completed.
To shorten the wait time of the interrupt, reduce the amount of data that access to other modules.
(3) Processing at program execution type change
When the program execution type is changed from the scan execution type to the interrupt, the CPU module
saves and restores the following data. (
• Data in the index register
• File register block number
Whether to save and restore the data above can be set in the PLC parameter dialog box.
If the data is not saved or restored, the overhead time of the corresponding interrupt program can be shortened.
( Page 468, Appendix 3.2 (3))
(4) Precautions
(a) When the same device is used
During execution of an instruction in a main routine program, an interrupt program may be executed,
suspending the processing of the instruction being executed.
If the same device is used for the main routine program and interrupt program, device data may become
inconsistent. In this case, take the following measures to prevent device data inconsistency.
• Moving device data to another device
Do not directly specify the device where the data is written by the interrupt program in the main routine
program. Use the data in another device by moving the data with the transfer instruction.
• Disabling interrupts with the DI instruction
Disable interrupts with the DI instruction if instructions that may cause inconvenience for the main routine
program are used. However, interrupts do not occur during access to the device of the corresponding
argument of the instruction. For this reason, data inconsistency will not occur in units of arguments.
CHAPTER 2 APPLICATION OF PROGRAMMING
Page 386, Section 4.6.3)
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