7 Inspection and Maintenance
7-8
CJ2 CPU Unit Hardware User’s Manual
The CJ-series PLCs can operate even when the Battery is exhausted or not installed.
To have operation continue when the Battery is exhausted or not installed, set the parameter in the PLC
Setup so that Battery errors are not detected.
The user program and parameter area data are saved in flash memory even when the Battery is
exhausted or not installed. I/O memory (such as the CIO Area), however, cannot be saved.
Operation is possible when the Battery is exhausted or not installed if the following two conditions both
apply.
• There is no need to save data in I/O memory.
• There is no need to use initial settings in the DM/EM Area, or the initial settings are made by the user
program.
Additional Information
You can use the function for automatic transfer from the Memory Card at startup to store data in
I/O memory and the DM/EM Area even when the Battery is exhausted or not installed.
The following table shows when the Battery is required according to the purpose of CPU Unit operation.
• The clock function cannot be used, so the values for the Calendar/Clock Area (A351 to A354) and the
Startup Time (A510 to A511) in the Auxiliary Area will be unstable. In addition, the times at which the
CPU Unit created files on the Memory Card will be unstable.
• The Total Power ON Time (A523), Power Interruption Time (A512 to A513), and Number of Power
Interruptions (A514) in the Auxiliary Area will all be all zeros at startup.
• Error log data will not be held in the Error Log Area (A100 to A199) in the Auxiliary Area at startup.
• Correct values may not be held in I/O memory (including the HR, DM, and EM Areas) at startup. In
the PLC Setup, set the IOM Hold Bit (A500.12) and the Forced Status Hold Bit (A500.13) to not be
held at startup.
• The value for the Output OFF Bit (A500.15) will become unstable. Moreover, when the Output OFF
Bit turns ON, the outputs of all Output Units will turn OFF. To prevent the outputs of all Output Units
from turning OFF at startup, take countermeasures such as writing the following program section into
the ladder program.
7-2-2 Operation When Battery Is Exhausted or Not Installed
Continuing Operation
Saving Data
Conditions for Operation
Saving I/O memory is required. The Battery is required.
Saving to I/O
memory is not
required.
DM/EM Area ini-
tial values are
required at star-
tup.
DM/EM Area initial values are
set from the Memory Card.
Automatic transfer from the Mem-
ory Card at startup is set. (Pin 2 is
set to ON.)
DM/EM Area initial values are
set from the user program.
Normal operation from flash
memory or operation using the
Memory Card is possible.
DM/EM Area initial values are not required at star-
tup.
Restrictions
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