Timer Interrupt (Interrupt In Constant Cycle) - Mitsubishi Electric MELSEC FX3U Programming Manual

FX /FX /FX Series Programmable Controllers
3G 3U 3UC
Programming Manual - Basic & Applied Instruction Edition
36.5

Timer Interrupt (Interrupt in Constant Cycle)

36.5.1 Timer interrupt (interrupt in constant cycle)
1. Outline
An interrupt routine is executed at every 10 to 99 ms without being affected by the operation cycle of a PLC.
2. Application
This type of interrupt is suitable when a certain program should be executed at high speed while the main
program operation time is long or when a program should be executed at a constant time interval in sequence
operations.
3. Basic program (programming procedure)
Step
0
Interrupt
pointer
I620
4. Number and operation of (three) timer interrupt pointers
I
Timer time: 10 to 99 (ms)
Timer interrupt pointer (6, 7 or 8)
An interrupt routine program is executed at every specified interrupt cycle time (10 to 99 ms). Use the type of
interrupt in control requiring cyclic interrupt processing regardless of the operating cycle of a PLC.
Input number
I6
I7
I8
*1. Cleared when the PLC mode is changed from RUN to STOP.
Caution
If the timer interrupt time is set to 9ms or less, the timer interrupt processing may not be executed in an
accurate cycle in the following cases. Therefore, using a time that is over 10 ms is recommended.
• When the interrupt program processing time is long
• When the main program contains an applied instruction which processing time is long
862
FNC 04
EI
FNC 06
FEND
When interrupt is
given at every 20 ms
FNC 03
IRET
END
An integer in the range from 10 to 99 is put in "
Example: "I610" indicates a timer interrupt at every 10 ms.
Main program
Timer interrupts are enabled after EI instruction.
Interrupts are
It is not necessary to program DI (disable
enabled
interrupt) if there is no zone where input
interrupts should be disabled.
Main
program
End of
FEND instruction indicates the end of the main
main program
program.
Make sure to describe an interrupt routine after
FEND instruction.
Interrupt subroutine
The interrupt routine is executed at every 20 ms.
Interrupt
Create a program to be executed as interrupt.
routine
IRET instruction returns the program execution
to the main program.
Interrupt return
Interrupt cycle (ms)
" in the pointer name.
36 Interrupt Function and Pulse Catch Function
36.5 Timer Interrupt (Interrupt in Constant Cycle)
Interrupt disable Flag
*1
M8056
*1
M8057
*1
M8058