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Number of Words to Back Up
The number of words to back up starting from D0 is set in the Number of CH of DM for backup Box
in the Startup Data Read Area in the PLC Setup.
Restoring DM Backup Data to the Built-in RAM When Power is Turned ON
The DM backup data can be restored to the built-in RAM when power is turned ON by selecting the
Restore D0- from backup memory Check Box in the Startup Data Read Area in the PLC Setup.
The DM backup data will be read from the backup memory even if the Clear retained memory area
(HR/DM/CNT) Check Box is selected in the PLC Setup.
Related Auxiliary Area Bits
Name
DM Backup Save
Start Bit
DM Backup Save
Flag
DM Backup
Restore Failed
Flag
CP1E CPU Unit Software User's Manual(W480)
Address
A751.15
The number of words in the DM Area specified in the Number of CH of
DM for backup Box in the Startup Data Read Area in the PLC Setup
are saved from the built-in RAM to the built-in EEPROM backup mem-
ory when this bit is turned ON.
This bit will not automatically turn OFF again if the bit turns ON. Design
the ladder program so that this bit is turned ON and OFF again using
upwardly differentiated bits.
If this bit is turned ON and OFF while the DM Backup Save Flag
(A751.14) is ON, it will be ignored and the data will not be backed up
again. To backup the data again, make sure that A751.14 is OFF and
then turn ON A751.15. A751.15 is turned OFF when the power supply
is turned ON.
A751.14
This flag turns ON when A751.15 is turned ON to start the saving
operation. This flag stays ON while data is being saved and turns OFF
when finished.
Use this flag to confirm when the DM backup operation has been com-
pleted.
The flag is turned OFF when the power supply is turned ON.
A751.11
This flag turns ON if the DM backup data could not be restored cor-
rectly. If this flag turns ON, data will not be read from the built-in
EEPROM backup memory to the RAM.
For example, if power was interrupted while data was being backed up,
the DM Area data would not be backed up properly and the next time
power is turned ON, the DM backup data will not be restored. If this
happens, this flag will be turned ON.
If the number of the backed up DM area words is different from the
Number of CH of DM for backup in the PLC Setup, this flag will be
turned ON.
This flag turns OFF in the following cases:
• Data is successfully restored from the built-in EEPROM backup
memory to the RAM when the power supply is turned ON.
• All memory is cleared.
16 Other Functions
Description
16
16-9
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