Mitsubishi Electric MELSEC-Q/L - Page 127

3 CONFIGURATION OF INSTRUCTIONS
3.9 Operation When the OUT, SET/RST, or PLS/PLF Instructions Use the Same Device
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3
PLF instructions using the same device
The PLF instruction turns ON the specified device when the execution command is turned OFF from ON. It turns OFF the
device at any other time (OFF to OFF, OFF to ON, or ON to ON). If two or more PLF instructions using the same device are
executed in one scan, each instruction turns ON the device when the corresponding execution command is turned OFF from
ON and turns OFF the device in other cases. For this reason, if multiple PLF instructions using the same device are executed
in a single scan, a device that has been turned ON by the PLF instruction may not be turn ON during one scan.
When using a refresh type CPU module and specifying output (Y) in the PLF instructions, the ON/OFF status of the device at
the execution of the last PLF instruction in the scan is returned as the output (Y).
[Ladder]
[Timing Chart]
• The ON/OFF timing of the X0 and X1 is different. (The specified device does not turn ON throughout the scan.)
• The X0 and X1 turn OFF from ON at the same time.
M0
X0
X1
PLF
M0PLF
M0
OFF
ON
END
END END
X0
X1
M0
OFF
OFF
ON
PLF
X0
X1
M0PLF
M0PLF
M0PLF
X0
X1
ON
M0 turns ON because
X0 goes OFF (ON OFF).
M0 turns OFF because X1
status is other than ON OFF.
M0 turns OFF because X1 status is
other than ON OFF.
(M0 remains OFF.)
M0 turns OFF because X0 status is
other than ON OFF
(M0 remains OFF.)
M0
OFF
ON
END
END
END
X0
X1
M0
OFF
OFF
PLF
X0
X1
M0PLF
M0PLF
M0PLF
X0
X1
ON
ON
M0 turns ON because
X0 goes OFF (ON OFF).
M0 turns ON because
X1 goes OFF (ON OFF).
(M0 remains ON.)
M0 turns OFF because X1 status is
other than ON OFF.
(M0 remains OFF.)
M0 turns OFF because X1 status is
other than ON OFF.