13
Safety Precautions
CJ-series EtherCAT Slave Units Operation Manual (W541)
The Controller outputs may remain ON or OFF due to deposition or burning
of the output relays or destruction of the output transistors.
As a countermeasure for such problems, external safety measures must be
provided to ensure safe operation of the system.
When the 24-V DC output (service power supply to the PLC) is overloaded or
short-circuited, the voltage may drop and result in the outputs being turned
OFF. As a countermeasure for such problems, external safety measures
must be provided to ensure safety in the system.
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. Serious accidents
may result from abnormal operation if proper measures are not provided.
The CPU Unit refreshes I/O even when the program is stopped (i.e., even in
PROGRAM mode). Confirm safety thoroughly in advance before changing
the status of any part of memory allocated to I/O Units, Special I/O Units, or
CPU Bus Units. Any changes to the data allocated to any Unit may result in
unexpected operation of the loads connected to the Unit. Any of the following
operation may result in changes to memory status.
• Transferring I/O memory data to the CPU Unit from a programming device.
• Changing present values in memory from a programming device.
• Force-setting/-resetting bits from a programming device.
• Transferring I/O memory files from a Memory Card or EM file memory to
the CPU Unit.
• Transferring I/O memory from a host computer or from another PLC on a
network.
Actual Operation
Check the user program, data, and parameter settings for proper execution
before you use them for actual operation.
Voltage and Current Inputs
Make sure that the voltages and currents that are input to the Units and
slaves are within the specified ranges.
Inputting voltages or currents that are outside of the specified ranges may
cause accidents or fire.
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