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PCHK
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7.17 Program control instructions
7.17.5 Program execution status check instruction (PCHK)
Remark
Non-execution indicates that the program execution type is a stand-by type.
Execution indicates that the program execution type is a scan execution type
(including during output OFF (during non-execution processing)), low speed
execution type or fixed scan execution type.
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 processing END processing END 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)