18 CP1E CPU Unit Instructions Reference Manual(W483)
Precautions for Safe Use
Observe the following precautions when using a CP-series PLC.

Handling

•To initialize the DM Area, back up the initial contents for the DM Area to backup memory using
one of the following methods.
•Set the number of words of the DM Area to be backed up starting with D0 in the Number of
CH of DM for backup Box in the Startup Data Read Area.
•Include programming to back up specified words in the DM Area to built-in EEPROM by turn-
ing ON A751.15 (DM Backup Save Start Bit).
•Check the ladder program for proper execution before actually running it on the Unit. Not checking
the program may result in an unexpected operation.
•The ladder program and parameter area data in the CP1E CPU Units are backed up in the built-in
EEPROM backup memory. The BKUP indicator will light on the front of the CPU Unit when the
backup operation is in progress. Do not turn OFF the power supply to the CPU Unit when the
BKUP indicator is lit. The data will not be backed up if power is turned OFF and a memory error
will occur the next time the power supply is turned ON.
•With a CP1E CPU Unit, data memory can be backed up to the built-in EEPROM backup memory.
The BKUP indicator will light on the front of the CPU Unit when backup is in progress. Do not turn
OFF the power supply to the CPU Unit when the BKUP indicator is lit. If the power is turned OFF
during a backup, the data will not be backed up and will not be transferred to the DM Area in RAM
the next time the power supply is turned ON.
•Before replacing the battery, supply power to the CPU Unit for at least 30 minutes and then com-
plete battery replacement within 5 minutes. Memory data may be corrupted if this precaution is
not observed.
•The equipment may operate unexpectedly if inappropriate parameters are set. Even if the appro-
priate parameters are set, confirm that equipment will not be adversely affected before transfer-
ring the parameters to the CPU Unit.
•Before starting operation, confirm that the contents of the DM Area is correct.
•After replacing the CPU Unit, make sure that the required data for the DM Area, Holding Area, and
other memory areas has been transferred to the new CPU Unit before restarting operation.
•Do not attempt to disassemble, repair, or modify any Units. Any attempt to do so may result in mal-
function, fire, or electric shock.
•Confirm that no adverse effect will occur in the system before attempting any of the following. Not
doing so may result in an unexpected operation.
•Changing the operating mode of the PLC (including the setting of the startup operating mode).
•Force-setting/force-resetting any bit in memory.
•Changing the present value of any word or any set value in memory.

External Circuits

•Always configure the external circuits to turn ON power to the PLC before turning ON power to the
control system. If the PLC power supply is turned ON after the control power supply, temporary
errors may result in control system signals because the output terminals on DC Output Units and
other Units will momentarily turn ON when power is turned ON to the PLC.
•Fail-safe measures must be taken by the customer to ensure safety in the event that outputs from
output terminals remain ON as a result of internal circuit failures, which can occur in relays, tran-
sistors, and other elements.
•If the I/O Hold Bit is turned ON, the outputs from the PLC will not be turned OFF and will maintain
their previous status when the PLC is switched from RUN or MONITOR mode to PROGRAM mode.
Make sure that the external loads will not produce dangerous conditions when this occurs. (When
operation stops for a fatal error, including those produced with the FALS instruction, all outputs from
PLC will be turned OFF and only the internal output status in the CPU Unit will be maintained.)