Safety Precautions - Mitsubishi QJ71LP21 Reference Manual

Before using this product, please read this manual and the relevant manuals introduced in this manual
carefully and pay full attention to safety to handle the product correctly.
The instructions given in this manual are concerned with this product. For the safety instructions of the
programmable controller system, please read the CPU module user's manual.
In this manual, the safety instructions are ranked as "DANGER" and "CAUTION".
!
DANGER
CAUTION
!
Note that the ! CAUTION level may lead to a serious consequence according to the circumstances.
Always follow the instructions of both levels because they are important to personal safety.
Please store this manual in a safe place and make it accessible when required. Always forward it to the
end user.
[Design Precautions]
• When the network develops a communication error, the station with the communication error will
enter into the following status.
Use the communication status data to form an interlock circuit in the sequence program that will
operate the system on the safe side. Erroneous output or malfunctioning could cause accidents.
(1) The remote master station will hold the data from before the communication error.
(2) The remote I/O station turns off all outputs. The output module of the remote I/O station can
clear/hold the output status at the time of error by using the remote I/O module parameters.
As the parameters are set to "clear" by default, the output module turns off the outputs at the
time of error. If it is required to hold the output in order to operate the system safely, set the
parameters to "hold".
• If a coaxial cable is disconnected, this may destabilize the line, and a data link communication
error may occur in multiple stations. Make sure to create an interlock circuit in the sequence
program so that the system will operate safely even if the above error occurs. Failure to do so
may result in a serous accident due to faulty output or malfunctions.
A - 1
• SAFETY PRECAUTIONS •
(Always read these instructions before using this equipment.)
Indicates that incorrect handling may cause hazardous conditions,
resulting in death or severe injury.
Indicates that incorrect handling may cause hazardous conditions,
resulting in medium or slight personal injury or physical damage.
DANGER
!
A - 1