Mitsubishi MELSEC-Q/L Programming Manual page 599

7.17
Program control instructions
(1) Processing when the execution type is converted with the program control instruction is as follows.
Execution type before change
Scan execution type
Initial execution type
Stand-by type
Low speed execution type
Fixed scan execution type
Once the fixed scan execution type program is changed to another execution type, it cannot be returned to the fixed scan
execution type.
(2) As program execution type conversions by PSCAN and PSTOP instructions occur at the END processing, such
conversions are impossible during program execution.
When different execution types have been set for the same program in the same scan, the execution type will be that
specified by the execution switching command that was executed last.
END processing
Execution
GHI
program name
*1: The order of "GHI" and "DEF" program execution is determined by the program settings parameters.
Switching from the fixed scan execution type program to the execution type program is performed in the following timing.
(a) For the Universal model QCPU, LCPU
The execution type is changed when the execution of the fixed scan execution type is stopped at the END
processing after the program control instruction execution.
(b) Basic model QCPU, High Performance model QCPU, Process CPU, and Redundant CPU
The execution of the fixed scan execution type is stopped at the execution of the program control instruction, and
the execution type is changed at the END processing.
(3) When the POFF instruction is executed, the output is turned OFF at the next scan, and the execution type will be the
stand-by type at the second next scan and later.
If executed prior to the output OFF processing, the program control instruction is ignored.
PSCAN
No change-remains
scan type execution.
Becomes stand-by type.
Becomes scan
execution type.
No change-remains
stand-by type
Low speed execution
Low speed execution
type execution is
type execution is
stopped, becomes
stopped, becomes
scan execution type
stand-by type from next
from the next scan.
scan.
(Execution from step 0)
Becomes scan
Becomes stand-by type.
execution type.
END processing
"ABC" GHI GHI
PSTO executes "ABC"
PSCAN executes "DEF"
Executed Instruction
PSTOP POFF
Output turned OFF in
next scan.
Becomes stand-by
type from the next
scan after that.
Ignored
Low speed execution
type execution is
stopped, and output is
turned OFF in the next
scan. Becomes
stand-by type from the
next scan after that.
Output turned OFF in
next scan.
Becomes stand-by
type from the next
scan after that.
END processing
*1 *1
DEF GHI
Converts "DEF" into the scan execution
type program and "ABC" to the stand-by
type program
PLOW
Becomes low speed
execution type.
No change -remains low
speed execution type.
Becomes low speed
execution type.
597
1
2
3
4
4
6
7
8