3 CPU Unit Operation
3-2-2
Backing Up Ladder Programs and PLC Setup
Ladder programs and the PLC Setup are automatically backed up to and restored from the built-in
EEPROM backup memory.
Backing Up Memory
Ladder programs and PLC Setup are backed up to the built-in EEPROM backup memory by trans-
ferring them from the CX-Programmer or writing them using online editing.
Restoring Memory
Ladder programs and PLC Setup are automatically transferred from the built-in EEPROM backup
memory to the RAM memory when power is turned ON again or at startup.
Precautions for Safe Use
The BKUP indicator on the front of the CPU Unit turns ON when data is being written to the built-
in EEPROM backup memory. Never turn OFF the power supply to the CPU Unit when the BKUP
indicator is lit.
3-2-3
I/O Memory Backup
I/O memory is backed up to the built-in EEPROM backup memory only when a bit in the Auxiliary Area
is turned ON to back up specified words in the DM Area.
Area
CIO Area
Work Area (W)
Timer Area (T)
Holding Area (H)
Counter Area (C)
Auxiliary Area (A)
DM Area
Number of words start-
(D)
ing from D0 set in the
Number of CH of DM for
backup Box in the Star-
tup Data Read Area in
the PLC Settings.
Ranges not given
above.
* The values will be cleared to all zeros at startup if the Clear retained memory area (HR/DM/CNT) Check Box is
selected in the PLC Settings.
3-6
Backup to built-in
N/NA-type CPU Unit with
EEPROM backup
no Battery mounted or
memory
Not backed up.
Cleared to all zeros.
Unstable when the power
supply is OFF for longer
than the I/O memory
backup time.
Initialized (For N/NA-type
CPU Units, status of bits
related to clock functions
is unstable when the
power supply is OFF for
longer than the I/O mem-
ory backup time.
The specified number of
The specified number of words starting from D0 is
words starting from D0 is
restored from the built-in EEPROM backup memory if
backed up by turning ON
the Restore D0- from backup memory Check Box is
A751.15 (DM Backup
selected in the Startup Data Read Area in the PLC Set-
Save Start Bit).
tings.
Not backed up.
Unstable when the power
supply is OFF for longer
than the I/O memory
backup time.
Status at startup
N/NA-type CPU Unit with
Battery mounted
E-type CPU Unit
The values immediately
before power interruption
are retained.
*
Initialized (For N/NA-type
CPU Units, status of bits
related to clock functions
are retained at their sta-
tus immediately before
power interruption.)
*
)
The values immediately
before power interruption
are retained.
CP1E CPU Unit Software User's Manual(W480)
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