Omron NJ501-4500 Manual page 24

Precautions for Safe Use
Battery Backup
The user program and initial values for the variables are stored in non-volatile memory in the CPU Unit.
The present values of variables with the Retain attribute and the values of the Holding, DM, and EM
Areas in the memory used for CJ-series Units are backed up by a Battery.
If the Battery is not connected or the Battery is exhausted, the CPU Unit detects a Battery-backup
Memory Check Error.
If that error is detected, variables with a Retain attribute are set to their initial values and the Holding,
DM, and EM Areas in memory used for CJ-series Units are cleared to all zeros.
Perform thorough verifications and provide sufficient measures to ensure that the devices perform safe
operation for the initial values of the variables with Retain attributes and the resulting operation.
Debugging
• Forced refreshing ignores the results of user program execution and refreshes I/O with the specified
values. If forced refreshing is used for inputs for which I/O refreshing is not supported, the inputs will
first take the specified values, but they will then be overwritten by the user program. This operation
differs from the force-set/reset functionality of the CJ-series PLCs.
• You cannot upload or download information for forced refreshing with the Sysmac Studio.
After downloading data that contain the forced refreshing targets, change to RUN mode and then
execute forced refreshing from the Sysmac Studio.
Depending on the difference in the forced status, the control system may operate unexpectedly.
• Do not specify the same address for the AT specification for more than one variable.
Doing so would allow the same entity to be accessed with different variable names, which would
make the user program more difficult to understand and possibly cause programming mistakes.
General Communications
• When you use data link communications, check the error information that is given in _ErrSta (Control-
ler Error Status) to make sure that no error has occurred in the source device. Create a user program
that uses reception data only when there is no error in the source device.
If there is an error in the source device, the data for the data link may contain incorrect values.
• Unexpected operation may result if inappropriate data link tables are set. Even if appropriate data link
tables have been set, confirm that the controlled system will not be adversely affected before you
transfer the data link tables. The data links start automatically after the data link tables are trans-
ferred.
• All CPU Bus Units are restarted when routing tables are transferred from Support Software to the
CPU Unit. Confirm that the system will not be adversely affected by restarting before you transfer the
routing tables.
• Tag data links will stop between related nodes while tag data link parameters are transferred during
Controller operation. Confirm that the system will not be adversely affected before you transfer the
tag data link parameters.
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NJ-series NJ Robotics CPU Unit User's Manual (W539)