Omron CJ-Series Operation Manual page 14

Application Precautions
!Caution Failure to abide by the following precautions could lead to faulty operation of
• Assembling the Units.
• Setting DIP switches or rotary switches.
• Connecting cables or wiring the system.
• Connecting or disconnecting the connectors.
the PLC or the system, or could damage the PLC or PLC Units. Always heed
these precautions.
• A CJ-series CPU Unit is shipped with the battery installed and the time
already set on the internal clock. It is not necessary to clear memory or
set the clock before application, as it is for the CS-series CPU Units.
• The user program and parameter area data in CJ1-H and CJ1M CPU
Units is backed up in the built-in flash 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.
• If, when using a CJ1M CPU Unit, the PLC Setup is set to specify using the
mode set on the Programming Console and a Programming Console is
not connected, the CPU Unit will start in RUN mode. This is the default
setting in the PLC Setup. (A CS1 CPU Unit will start in PROGRAM mode
under the same conditions.)
• When creating an AUTOEXEC.IOM file from a Programming Device (a
Programming Console or the CX-Programmer) to automatically transfer
data at startup, set the first write address to D20000 and be sure that the
size of data written does not exceed the size of the DM Area. When the
data file is read from the Memory Card at startup, data will be written in
the CPU Unit starting at D20000 even if another address was set when
the AUTOEXEC.IOM file was created. Also, if the DM Area is exceeded
(which is possible when the CX-Programmer is used), the remaining data
will be written to the EM Area.
• Fail-safe measures must be taken by the customer to ensure safety in the
event of incorrect, missing, or abnormal signals caused by broken signal
lines, momentary power interruptions, or other causes.
• Interlock circuits, limit circuits, and similar safety measures in external cir-
cuits (i.e., not in the Programmable Controller) must be provided by the
customer.
• Always 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 sup-
ply, 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 Units remain ON as a result of internal cir-
cuit failures, which can occur in relays, transistors, 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
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