Mitsubishi MELSEC QCPU Programming Manual page 93

3 CONFIGURATION OF INSTRUCTIONS
(4) PLF instructions using the same device
The PLF instruction turns ON the specified device when the PLF command turns ON from
OFF. It turns OFF the specified device at any other time (OFF
ON).
When two or more PLF instructions using the same device are programmed in one scan, each
PLF instruction turns OFF the specified device when the corresponding PLF command turns
OFF from ON and it turns OFF the specified device at any other time.
For this reason, when two or more PLF instructions using the same device are programmed in
one scan, the device that has been turned ON by the PLF command may not turn ON again
throughout the scan.
[Circuit]
X0
X1
[Timing Chart]
• The ON/OFF timing of the X0 and X1 is different. (The specified device does not turn ON
throughout the scan.)
END
X0
X1
OFF
OFF
M0
• The X0 and X1 turn OFF from ON at the same time.
END
OFF
X0
ON
X1
OFF
M0
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PLF M0
PLF M0
X0
PLF
X1
OFF
ON
M0 turns OFF because X1 is
not turning OFF from ON.
M0 turns ON because X0
turns OFF from ON.
X0
PLF
X1
OFF
ON
M0 turns ON because X1 turns
OFF from ON. (M0 stays ON.)
M0 turns ON because
X0 turns OFF from ON.
X0
M0
PLF
X1
PLF M0
PLF
END END
ON
M0 turns OFF because X1
turns OFF from ON.
(M0 stays OFF.)
M0 turns OFF because X0 is not turning
OFF from ON. (M0 stays OFF.)
X0
M0
PLF
X1
PLF M0
PLF
END
END
M0 turns OFF because X1
is not turning OFF from ON.
(M0 stays OFF.)
M0 turns OFF because X0 is not turning
OFF from ON.
MELSEC-Q/QnA
OFF, OFF ON, and ON
M0
M0
M0
M0
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