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Mitsubishi Electronics FX3G User Manual

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93
FX
3S
/FX
3G
/FX
3GC
/FX
3U
/FX
3UC
 Series
Programming Manual - Basic & Applied Instruction Edition
4 Devices in Detail
4.3 Auxiliary Relay [M]
1
Introdu
ction
2
Ov
ervi
ew
3
Instruction 
Li
st
4
D
evices 
in Det
ai
l
5
Specifi
ed the
De
vice
 &
 
C
onst
ant
6
Bef
ore
 
Pr
og
ra
mmi
ng
7
Bas
ic 
Instruction
8
FN
C00-FN
C0
9
Program Fl
ow
9
FNC
10-FN
C19
Mov
e & Com
pare
10
FNC
20-FNC
29
Arith. & Lo
gi
c 
Operati
on
2. Latched (battery backed) type
When the power is turned OFF while the PLC is operating, all of the output relays and general type auxiliary relays
turn OFF.
When restoring the power again, all of the output relays and general type auxiliary relays remain OFF except those
whose input condition is ON. In some output relays and auxiliary relays, however, the ON/OFF status just before
power failure should be stored and then replicated when restoring the power, depending on control targets. In such a
case, use latched (battery backed) type auxiliary relays.
In FX
3U
/FX
3UC
 PLCs, latched (battery backed) type devices are backed up by the battery built into the PLC.
In FX
3S
/FX
3G
/FX
3GC
 PLCs, latched type devices are backed up by the EEPROM built into the PLC. When the optional
battery is installed in FX
3G
/FX
3GC
 PLCs, the battery backs up some general type devices.
→ For details on backup method against power failure,
refer to Section 2.6.
The figure on the left shows an operation example of M600
(latched [battery backed] type device) in a self-holding
circuit.
When X000 turns ON and M600 turns ON in this circuit,
M600 holds its operation by itself even if X000 is opened.
Because M600 is a latched (battery backed) type device, it
remains activated when the operation is restarted even after
X000 has turned OFF due to power failure. If an NC contact
of X001 is opened when the operation is restarted, however,
M600 is deactivated.
The figure on the left shows a circuit using the SET and RST
instructions.
1) Application example of latched (battery backed) type auxiliary relays
In some cases, the table should be restarted in the same
direction as the direction selected just before power failure.
X000 = ON (at the left limit) 
→ M600 = ON→ The table is
driven rightward. 
→ The power is turned OFF. → The table
is stopped in an intermediate position. 
→ The table is
restarted (M600 = ON). 
→ X001 = ON (at the right limit) →
M600 = OFF, M601 = ON 
→ The table is driven leftward.
2) Method for using a fixed latched (battery backed) type auxiliary relay as a general type auxiliary relay
When using a fixed latched (battery backed) type auxiliary relay as a general type auxiliary relay, provide a reset
circuit shown in the figure below around the head step in the program.
Ex. FX
3U
/FX
3UC
 PLCs
X000
M600
X001
PLC
Backup against power failure
(self-holding circuit)
M600
X000
X001
PLC
Backup against power failure
(set/reset circuit)
SET
M600
RST
M600
X000
M600
X001
M600
Rightward
drive
command
X001
M601
X000
M601
Leftward drive
command
Left limit
Limit switch
LS1 (X000)
Right limit
Limit switch
LS2 (X001)
Table in reciprocating motion
Motor with brake
M8002
Initial pulse
FNC 40
ZRST
M1024
M1999
M1024 to M1999 are initialized.