16 Other Functions
16-8
CP1E CPU Unit Software User’s Manual(W480)
16-3 DM Backup Function
This section describes the function that saves specified words from the DM Area in the built-in
EEPROM backup memory.
The contents of the DM Area (D) will become unstable if the power supply is interrupted for longer than
the backup time of the built-in capacitor (50 hours for an E-type CPU Unit, 40 hours for an N/NA-type
CPU Unit without a Battery). The contents of the specified words in the DM Area data can be backed up
from RAM to the built-in EEPROM backup memory during operation by turning ON a bit in the Auxiliary
Area. The number of DM Area words to back up is specified in the Number of CH of DM for backup Box
in the PLC Setup. If the Restore D0- from backup memory Check Box is selected in the PLC Setup, the
backup data will automatically be restored to RAM when the power is turned back ON so that data is
not lost even if power is interrupted.
Conditions for Executing Backup
Specified words starting from D0 in the built-in RAM can be saved to the built-in EEPROM backup
memory by turning ON A751.15. (These words are called the DM backup words and the data is
called the DM backup data.) A751.15 (DM Backup Save Start Bit) can be used in any operating
mode (RUN, MONITOR, or PROGRAM mode).
Words that can be Backed Up
• E-type CPU Units: D0 to D1499
• N/NA-type CPU Units: D0 to D6999
16-3-1 Backing Up and Restoring DM Area Data
Overview
CP1E CPU Unit
A751.15 (DM Backup Save Start Bit) turned ON.
Built-in RAM
DM Area (D)
Specified number
of words
DM backup data
Data
backed up.
Data
restored.
Built-in EEPROM Backup
Memory
~
D0
D (n-1)
Specify the number of words
starting from D0 in the
Number of CH of DM for
backup Box in the Startup
Data Read Area in PLC
Setup.
DM backup data is restored to the RAM when power supply is turned ON
again if the Restore D0- from backup memory Check Box is selected in the
Startup Data Read Area in the PLC Setup.
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