C9-1
IM 34M06H62-02E 2nd Edition : June 2008-00
C9. Disable Backup Function
The Disable Backup Function (NBKUP) can be used to suspend the automatic
storing of parameters to the EEPROM. Use this function to protect the EEPROM if
parameters are updated frequently.
The module has two types of parameters: stored and non-stored. Stored parameters
preserve their data in EEPROM even when the module is powered down provided
NBKUP is set to 0 (backup). Beware that there is a limit to the number of times stored
parameters can be updated.
For details on whether a parameter is stored or non-stored, see the individual parameter
table or the list of registers.
The default value of the Disable Backup Function (NBKUP) parameter is 0 (backup).
With NBKUP=0, when a stored parameter is updated, its data is written to the EEPROM
and thus preserved even if power supply is turned off.
As there is a maximum limit to the number of write operations (approx. 100,000 times)
allowed for the EEPROM, be careful not to exceed the limit. Once the limit is reached, a
hardware failure may occur and subsequent storage is not guaranteed.
If stored parameters are updated frequently, set NBKUP to 1 (no backup) to protect the
EEPROM. In this case, stored parameters will not be written to the EEPROM when
updated. Thus, when the module is turned off and turned on again, the parameters revert
to their last stored values and must be updated again if required.
Do not attempt to change the value of the Disable Backup Function (NBKUP) parameter
from 1 (no backup) to 0 (backup) by writing to the parameter.
To enable the backup function, simply switch off and then switch on the module. Since
the NBKUP parameter is not a stored parameter, its value will reset to 0 (backup) after
power up.
TIP
If you update some parameters after changing the NBKUP parameter to 0 (backup), and then switch off
and switch on the module, you may find that not all parameter values are what you expect. This is
because the module stores parameters only when they are changed.
Table C9.1 Disable Backup Function Parameter
Data Position Number
Symbol Description Unit Data Range
Default
Value
Attribute
Stored
Loop 1 Loop 2 Loop 3 Loop 4
75 NBKUP
Disable Backup
Function
None
0: Enable backup to EEPROM
1: Disable backup to EEPROM
0 RW —
CAUTION
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