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FX3S/FX3G/FX3GC/FX3U/FX3UC Series
Programming Manual - Basic & Applied Instruction Edition
8 Program Flow – FNC 00 to FNC 09
8.4 FNC 03 – IRET / Interrupt Return
Program example
Interrupts are usually disabled in PLCs.
Use EI instruction to enable interrupts.
When X000 turns ON while the main program is executed,
instructions after the interrupt routine pointer I001 are
executed, and the program execution returns to the original
main program by IRET instruction.
The timer interrupt of the pointer I620 is executed every timer
time of 20 ms, and the program execution is returned to the
original main program by IRET instruction each time.
The high-speed counter interrupt of the pointer I010 is
executed when the current value of a high-speed counter
becomes equivalent to a value specified by DHSCS (FNC 53)
instruction.
The program execution returns to the original main program by
IRET instruction.
Make sure to program an interrupt pointer (I***) as a label after
FEND instruction.
I620
C255
I001
FNC 04
EI
FNC 06
FEND
FNC 03
IRET
FNC 03
IRET
Interrupt
pointer
Interrupt
pointer
The rising edge of X000 is detected.
Interrupt every 20 ms
M8000
Main program
Input interrupt
routine
Timer interrupt
routine
I010
FNC 03
IRET
Interrupt
pointer
High-speed counter
High-speed counter
routine
END