Mitsubishi MELSEC-Q/L

604
PCHK
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)