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3.9
Operation when the OUT, SET/RST, or PLS/PLF
Instructions Use the Same Device
The following describes the operation for executing multiple instructions of the OUT, SET/RST, or PLS/PLF that use the same
device in one scan.
(1) OUT instructions using the same device
Do not program more than one OUT instruction using the same device in one scan. If the OUT instructions using the
same device are programmed in one scan, the specified device will turn ON or OFF every time the OUT instruction is
executed, depending on the operation result of the program up to the relevant OUT instruction. Since turning ON or OFF
of the device is determined when each OUT instruction is executed, the device may turn ON and OFF repeatedly during
one scan. The following diagram shows an example of a ladder that turns the same internal relay (M0) with inputs X0
and X1 ON and OFF.
[Ladder]
X0
X1
[Timing Chart]
END
ON
OFF
X0
ON
X1
OFF
OFF
M0
With the refresh type CPU module, when the output (Y) is specified by the OUT instruction, the ON/OFF status of the last
OUT instruction of the scan will be output.
(2) SET/RST instructions using the same device
(a) The SET instruction turns ON the specified device when the execution command is ON and performs nothing when
the execution command is OFF.
For this reason, when the SET instructions using the same device are executed two or more times in one scan, the
specified device will be ON if any one of the execution commands is ON.
(b) The RST instruction turns OFF the specified device when the execution command is ON and performs nothing
when the execution command is OFF.
For this reason, when the RST instructions using the same device are executed two or more times in one scan, the
specified device will be OFF if any one of the execution commands is ON.
M0
M0
X0
M0
X1
M0
END
ON
M0 turns OFF because X1 is OFF.
M0 turns ON because X0 is ON.
X0
M0
X1
M0
END
M0 turns ON because X1 is ON.
M0 remains OFF because X0 is OFF.
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