831
FX
3U
/FX
3UC
Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
36 Operation of Special Devices (M8000 -, D8000 -)
36.2 Supplement of Special Devices (M8000 - and D8000 -)
31
FN
C
275-FN
C
279
Da
ta
Tr
ans
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32
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280
-F
N
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28
9
H
igh Speed
Pr
oces
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33
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290-FN
C
299
Ext
ensi
on Fi
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R
egi
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34
SF
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Pr
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35
In
te
rru
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t
Funct
ion
36
Sp
e
cia
l De
vic
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37
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rro
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Appl
ic
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36.2.3
Battery voltage low detection [M8005 and M8006]
This special device detects low voltage in the lithium battery for memory backup.
When the PLC detects low battery voltage, BATT (BAT) light turns on. The following program demonstrates
it’s use.
36.2.4
Power failure detection time [D8008, M8008 and M8007]
1. FX
3U
PLC (AC power supply type)
The table below shows the allowable momentary power failure time in FX
3U
PLCs (AC power supply type).
2. FX
3UC
PLC (DC power supply type)
The allowable momentary power failure time in the FX
3UC
PLC (DC power supply type) is 5 ms. Do not
overwrite the power failure detection time in device D8008.
36.2.5
Scan time (monitor) [D8010 to D8012]
The present value, minimum value and maximum value of the PLC scan time (operation time) are stored in
D8010, D8011 and D8012 respectively.
When using the constant scan mode, the values stored in these devices include the waiting time for the
constant scan time.
Supply voltage
Allowable momentary power
failure time
100V AC system
10 ms
200V AC system
Setting range: 10 to 100 ms
Set a value to D8008.
Default: 10 ms
M8005
Battery
voltage low
"Battery voltage low"
Y001
M8006 latches the battery voltage low.
0
1 scan time
Power failure
detection time
D8008
10ms
Approx. 5 ms
AC power supply
M8000: RUN monitor
M8007: Momentary
power failure
detection
M8008: Power failure
detected
1 scan time
Power failure detection time
D8008
5ms
Approx. 2 ms
DC power supply
M8000:RUN monitor
M8007:Momentary
power failure
detection
M8008:Power failure
detected
D8010: Present value
D8011: Minimum value
D8012: Maximum value
The values stored in these devices can be
monitored from peripheral equipment.