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Operation Processing At Momentary Power Failure - Mitsubishi Electric MELSEC-A Series User Manual

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4.A2CCPU
- - - - - - - - - - - - - - - - - - - - MELSEC-A
4.1.6
Operation processing at momentary power failure
I
The A2C detects momentary power failure when the input line voltage to the
power supply module falls below the defined range.
The A2C performs two different kinds of operation processing depending on
the length of momentary power failure time across 20 msec allowable value.
(1) Momentary power failure within 20 msec
(a) The operation processing is stopped with the output retained.
(b) The operation processing resumed where normal status is restored.
(c) The watch dog timer (WDT) keeps timing while the operation is at a
stop. For instance, if the WDT and scan time settings are 200 msec
and 190 msec respectively, an momentary power failure of 20 msec
will result is a WDT error.
o
I
.
Power recovery
Momentary power failure occurs.
(Sequence program continues.)
END
0
1
/
END
0
END
I
I
"\
i
I
I
I
~ND
-+-----+-
'-------y'
Sequence
processing
The A2C stops
program
operation.
operation
WDTtiming
Fig. 4.4 Momentary Power Failure within 20 msec
(2)
Momentary power failure over 20 msec
The A2C is reset. The A2C performs the initial start processing as it
does when it is turned on or reset by the RUN key switch operation.
o
END
Power failure (Initial start)
/0
'i
I
1===11--
~Sequence
I L
Initial
program
.
operation
processing
The A2C stops operation.
'--cE'ND
processing
Momentary power failure occurs.
END
0
j
I
I
Fig. 4.5 Momentary Power Failure over 20 msec
4-9

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