Mitsubishi FX3U Series Programming Manual page 207

FX /FX Series Programmable Controllers
3U 3UC
Programming Manual - Basic & Applied Instruction Edition
Program example
M8000
C255
Interrupt
The rising edge of X000 is detected.
pointer
I001
Interrupt
Interrupt at every 20 ms
pointer
I620
Interrupt
High speed counter
pointer
I010
FNC 04
EI
Main program
FNC 06
FEND
Input interrupt
routine
FNC 03
IRET
Timer interrupt
routine
FNC 03
IRET
High speed counter
routine
FNC 03
IRET
END
8 Program Flow – FNC 00 to FNC 09
8.4 FNC 03 – IRET / Interrupt Return
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 at every
timer time of 20 ms, and the program execution is
returned to the original main program by IRET instruction
at every 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.
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