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MELSEC-Q
4 SEQUENCE PROGRAM CONFIGURATION AND EXECUTION
CONDITIONS
4.5 Operation Processing during Momentary Power Failure
The High Performance model QCPU detects a momentary power failure when the
input power voltage supplied to the power supply module is lower than the regulated
ranges.
When the High Performance model QCPU detects a momentary power failure, the
following operation processing is performed:
(1) When momentary power failure occurs for a period shorter than the
permitted power failure time
(a) The output is maintained when the momentary power failure occurs, and file
name of the file accessed and error history are logged. Then the system
interrupts the operation processing. (The timer clock continues.)
(b) When there is an SFC continue specification, a system saving processing is
performed.
(c) When a momentary power failure ends, the operation processing is
resumed.
(d) Even if the operation is interrupted due to momentary power failure, the
watch dog timer (WDT) measurement continues. For example, if the GX
Developer PLC parameter mode WDT setting is set at 200 ms, when a
momentary failure of 15 ms occurs at scan time 190 ms, the watch dog
timer error is set.
QCPU interrupts the operation.
END
Power recoveryMomentary power failure occurrence
ENDEND
0
Fig.4.6 Operation Processing When Momentary Power Failure Occurs
(2) When a power failure occurs for a period longer than the permitted
power failure time
The High Performance model QCPU starts initially. (PLC power is turned on.)
The same operation processing as that after the following operation occurs.
• Power ON
• Resetting using RESET/L. CLR switch
• Remote setting using GX Developer
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