Mitsubishi Electric MELSEC iQ-R Series User Manual page 598

■Fixed scan execution type
The program is executed at each specified time.
The time can be set from that of the first operation cycle up to 60000[ms] (in integer multiples of the first operation cycle).
Processing is prioritized by execution interval length and starts by processing programs with the shortest intervals.
To execute a fixed scan execution type program, it is necessary to change its status to execution enabled
through EI instruction.
The fixed scan execution type program is executed at the start of the next fixed scan after EI instruction is issued.
The fixed scan interval counter is monitored after the power is turned ON and then used to determine execution conditions.
Fixed scan execution type program 1
Operation cycle processing
Fixed scan execution type program 2
Normal execution type program
Fixed scan execution type program
enabled/disabled
Fixed scan execution type programs cannot be executed if they have been disabled (DI) from a normal
execution type program.
• Interruption of processing
Other high-priority processing can interfere with program execution processing in some cases.
If processing interference occurs due to interruption while running a fixed scan execution type program, the processing will
resume after the interrupt processing completes. In addition, all further execution cycles are ignored until the processing
completes if the processing time is exceeded for the fixed scan interval. Execution resumes from the next execution cycle
after the processing completes.
Fixed scan execution type program 1
Operation cycle processing
Fixed scan execution type program 2
APPX
596
Appendix 2 Motion Module Programs
Priority
High
Fixed cycle execution type program 1 execution cycle
EI
instruction
Low
Disabled
Priority
High
Fixed scan execution type program 1 execution cycle
Low
Fixed scan execution type program 2 execution cycle
Operation cycle processing execution cycle
Enabled
Fixed scan execution type program 2 execution cycle
Operation cycle processing execution cycle
Processing time Processing
exceeded completes for the
exceeded portion
Time
No execution
until the next
execution cycle
Time