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Interrupt Tasks Section 2-3
If more than one interrupt occurs at the same time, the interrupt tasks will be
executed in the following order: Input interrupt tasks (Direct Mode or Counter
Mode), High-speed interrupt tasks, External interrupt tasks, Scheduled inter-
rupt task.
If more than one of the same type of interrupt occurs at the same time, the
one with the lower task number will be executed first.
Keep in mind that the above order of execution means that time may be
required to execute a programmed task even after an interrupt has occurred if
the user program allows the possibility of more than one interrupt occurring at
the same time. For example, the user must give special consideration to the
scheduled interrupt, which may not be executed at the expected time if other
interrupts occur.
2-3-2 Interrupt Task Flags and Words
Maximum Interrupt
Task Processing Time
(A440)
The maximum processing time for an interrupt task is stored in binary data in
0.1-ms units and is cleared at the start of operation.
Interrupt Task with
Maximum Processing
Time (A441)
The interrupt task number with maximum processing time is stored in binary
data. Here, 8000 to 80FF hex correspond to task numbers 00 to FF hex.
A441.15 will turn ON when the first interrupt occurs after the start of opera-
tion. The maximum processing time for subsequent interrupt tasks will be
stored in the rightmost two digits in hexadecimal and will be cleared at the
start of operation.
Interrupt Task Error
Flag (Nonfatal Error)
(A402.13)
If Interrupt Task Error Detection is turned ON in the PLC Setup, the Interrupt
Task Error Flag will turn ON if an interrupt task error occurs.
Interrupt Task Error
Flag (A426.15)/Task
Number Generating
the Interrupt Task
Error (A426.00 to
A426.11)
If A402.13 turns ON, then the following data will be stored in A426.15 and
A426.00 to A426.11.
Task Number when
Program Stopped
(A294)
The type of task and the current task number when a program stops due to a
program error will be stored in the following locations.
A402.13 Interrupt Task Error
Description
A426.15 A426.00 to A426.11
Interrupt Task Error (If
Interrupt Task Error
Detection is turned ON
in the PLC Setup)
When trying to refresh
I/O for a large number
of words using
IORF(097) from an
interrupt task while a
CJ-series Special I/O
Unit is being refreshed
by cyclic I/O refreshing.
ON The unit number of the
CJ-series Special I/O
Unit being refreshed
will be stored in 12 bits
of binary data (unit
number 0 to 95: 000 to
05F hex).
Type A294
Interrupt task 8000 to 80FF hex (corresponds to interrupt task 0 to 255)
Cyclic task 0000 to 001F hex (corresponds to task 0 to 31)
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