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FX3G/FX3U/FX3UC Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
36 Interrupt Function and Pulse Catch Function
36.2 Common Items
31
FNC275-FNC279
Data
Transfer 3
32
FNC280-FNC289
High Speed
Processing 2
33
FNC290-FNC299
Extension File
Register
34
FNC300-FNC305
FX
3U
-CF-ADP
35
SFC•STL
Programming
36
Interrupt
Function
37
Special Device
38
Error Code
A
Version Up
Information
B
Execution Times
2) Program example
In the program example shown below, when M8053 is set to ON by M20, the interrupt input I301 triggered by
X003 is disabled.
36.2.2 Related items
1. Using the I/O refresh function (REF instruction)
When controlling an input relay or output relay in an interrupt program, the I/O refresh instruction REF (FNC 50) can
be used to acquire the latest input information and immediately output the operation result. As a result, high speed
control is achieved without being affected by the operation cycle of the PLC.
2. Interrupt operation while FROM/TO instruction is executed
The interrupt operation is executed as follows depending on the ON/OFF status of the special auxiliary relay M8028.
1) While M8028 is OFF
While FROM/TO instructions are being executed, interrupts are automatically disabled. Input interrupts and timer
interrupts are not executed.
Interrupts generated during this period are immediately executed when the execution of FROM/TO instructions
are completed.
FROM/TO instruction can be used in an interrupt program when M8028 is OFF.
2) While M8028 is ON
When an interrupt is generated while a FROM/TO instruction is being executed, execution of the FROM/TO
instruction is paused and the interrupt is immediately executed.
FROM/TO instructions cannot be used in an interrupt routine program when M8028 is ON.
36.2.3 Cautions on use (common)
This section explains common cautions on using the interrupt function or pulse catch function.
Specific cautions on each interrupt function are explained in the description of each interrupt function.
1. Processing when many interrupts are generated
When many interrupts are generated in turn, priority is given to the first one. When many interrupts are generated at
the same time, priority is given to the one having the smallest pointer number.
While an interrupt routine is being executed, other interrupts are disabled.
2. When double interrupt (interrupt during another interrupt) is required [interrupt function]
Usually, interrupts are disabled in an interrupt routine (program).
When the EI (FNC04) and DI (FNC05) instructions are programmed in an interrupt routine in FX
3U/FX3UC PLCs, up to
two interrupts can be accepted.
Double interrupts are not available in FX
3G PLCs.
M8053
Interrupt
routine
Interrupts are
enabled
FNC 04
EI
FNC 06
FEND
FNC 03
IRET
I301
Interrupt
pointer
Command to disable
an interrupt triggered
by X003
When the rising edge of X003 is detected
END
M20