Mitsubishi Electric FX3G SERIES Programming Manual page 92

FX /FX /FX Series Programmable Controllers
3G 3U 3UC
Programming Manual - Basic & Applied Instruction Edition
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 /FX PLCs, latched (battery backed) type devices are backed up by the battery built into the PLC.
3U 3UC
In FX PLCs, latched type devices are backed up by the EEPROM built into the PLC. When the optional battery is
3G
installed, the battery backs up some general type devices.
X000
M600
Backup against power failure
X000
X001
Backup against power failure
1) Application example of latched (battery backed) type auxiliary relays
Limit switch
Left limit
LS1 (X000)
Table in reciprocating motion
X000
M600
X001
M601
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 /FX
3U
M8002
Initial pulse
90
X001
M600
PLC
(self-holding circuit)
SET M600
RST M600
PLC
(set/reset circuit)
Limit switch
Right limit
LS2 (X001)
Motor with brake
X001
M600
Rightward
drive
command
X000
M601
Leftward drive
command
PLCs
3UC
FNC 040
M1024
ZRST
M1024 to M1999 are initialized.
→ For details on backup method against power failure,
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.
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.
M1999
4 Devices in Detail
4.3 Auxiliary Relay [M]
refer to Section 2.6.