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7 APPLICATION INSTRUCTIONS
7.17 Program Control Instructions
The PCHK instruction is in conduction when the program of the specified file name (target program) is in
execution, and the instruction is in non-conduction when the program is in non-execution.
When the target program is set to non-execution (stand-by type) with the POFF instruction, the PCHK
instruction is in conduction while the non-execution processing of the target program is being performed.
At the END processing of the scan where the non-execution processing is completed, the target program is
put into non-execution (stand-by type), and the PCHK instruction is brought into non-conduction.
Therefore, note that if the PCHK instruction is executed for the program where the non-execution processing
has been completed by the POFF instruction, the PCHK instruction may be brought into conduction.
The following chart shows the operation performed when program A executes the POFF instruction of
program B and program C executes the PCHK instruction of program B with the programs being executed in
order of program A, program B, and program C.
Program A
PCHK B
Continuity
Non-continuity
Program B
Program C
Scan
execution
Scan
execution
Scan
execution
Scan
execution
Scan
execution
Scan
execution
Scan
execution
Scan
execution
Scan
execution
END processingEND processingEND processing
POFF instruction is
executed in program B
Non-execution processing
is performed.
Program B execution type change
(Scan execution type to stand-by type)
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