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MELSEC-Q/QnA
3 CONFIGURATION OF INSTRUCTIONS
3.9 Operation when OUT, SET/RST, or PLS/PLF Instructions Use
the Same Device
The following describes the operation for executing multiple instructions of 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 circuit that turns the same internal relay (M0)
with inputs X0 and X1 ON and OFF.
[Circuit]
M0
X0
M0
X1
[Timing Chart]
M0
M0
M0
M0
M0 turns ON because X0 is ON.
M0 turns OFF because X1 is OFF.
M0 remains OFF because X0 is OFF.
M0 turns ON because
X1 is ON.
OFF
ON
ON
OFF
ON
END
END END
0
1
M0
X0
X0
X1 X1
OFF
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.
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