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1-3SectionStructure and Operation
18
When an interrupt is generated during execution of the main program, main pro-
gram execution is interrupted immediately and the interrupt program is execut-
ed. The following diagram shows the cyclic operation of the CPM2B when an
interrupt program is executed.
Normally, the results of interrupt program execution are transferred to I/O
memory just after program execution (during I/O refreshing), but IORF(97) can
be used to refresh a specified range of I/O words during execution of the inter-
rupt program. The specified range of I/O words will be refreshed when IORF(97)
is executed.
The normal cycle time is extended by the time required for execution of the inter-
rupt program.
Refer to Section 7 PC Operations and Processing Time in the CPM1/CPM1A/
CPM2A/CPM2C/SRM1(-V2) Programmable Controllers Programming Manual
(W353) for more details and precautions on the cycle time.
Cycle
time
Overseeing processes
Main program
I/O refreshing
RS-232C port servicing
Peripheral port servicing
Interrupt generated.
Interrupt program
Caution Although IORF(97) can be used in interrupt subroutines, you must be careful of
the interval between IORF(97) executions. If IORF(97) is executed too frequent-
ly, a fatal system error may occur (FALS 9F), stopping operation. The interval
between executions of IORF(97) should be at least 1.3 ms + total execution time
of the interrupt subroutine.
IORF(97) can be executed in the program to refresh a specified range of I/O
words. The specified I/O words will be refreshed when IORF(97) is executed.
IORF(97) can be used to refresh I/O from the main program or the interrupt pro-
gram.
Interrupt Program
Execution
Immediate Refreshing