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38 SYSMAC CP1L/CP1E Introduction Manual
3-4 Power Testing CP1L
3
Mounting and Wiring
Note Battery
• Using a battery
The battery maintains the internal clock and retained regions of I/O memory
while the power supply is OFF.
If no battery is installed, or if the installed battery is running low, the internal
clock will stop, and data in the retained regions of I/O memory will be lost.
Data such as user programs and PLC system settings are not lost even when
the power is OFF and no battery is installed.
For details on replacing the battery, refer to 10-2 Replacing User-servicable
Parts of CP Series CP1L CPU Unit User’s Manual (W462) or 7-2 Replacing
the Battery in N-type CPU Units of CP Series CP1E CPU Unit Hardware
User's Manual (W479).
• Battery-free operation
If there is no need to reference the PLC clock and RAM data, CP1L can be
used without a battery (battery-free operation).
For details, refer to 6-5 Battery-free Operation of CP Series CP1L CPU Unit
User’s Manual (W462).
Caution With an CP1E E-type CPU unit or with an N-type CPU unit without a Battery, the
contents of the DM Area (D) *, Holding Area (H), the Counter Present Values (C),
the status of Counter Completion Flags (C), and the status of bits in the Auxiliary
Area (A) related to clock functions may be unstable when the power supply is turned
ON.
*This does not apply to areas backed up to EEPROM using the DM backup
function.
If the DM backup function is being used, be sure to use one of the following
methods for initialization.
1. Clearing All Areas to All Zeros
Select [Clear Held Memory (HR/DM/CNT) to Zero] in the [Startup Data Read]
area in the PLC Setup.
2. Clearing Specific Areas to All Zeros or Initializing to Specific Values
Make the settings from a ladder program.
If the data is not initialized, the unit or device may operate unexpectedly because of
unstable data.
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