Mitsubishi Electric MELSEC iQ-R Series User Manual page 5

[Design Precautions]
WARNING
● Especially, when a remote programmable controller is controlled by an external device, immediate
action cannot be taken if a problem occurs in the programmable controller due to a communication
failure. To prevent this, configure an interlock circuit in the program, and determine corrective actions
to be taken between the external device and CPU module in case of a communication failure.
● Do not write any data to the "system area" and "write-protect area" of the buffer memory in the
module. Also, do not use any "use prohibited" signals as an output signal from the CPU module to
each module. Doing so may cause malfunction of the programmable controller system. For the
"system area", "write-protect area", and the "use prohibited" signals, refer to the user's manual for the
module used.
● If a communication cable is disconnected, the network may be unstable, resulting in a communication
failure of multiple stations. Configure an interlock circuit in the program to ensure that the entire
system will always operate safely even if communications fail. Incorrect output or malfunction due to a
communication failure may result in an accident.
● If the redundant system fails, control of the entire system may not be maintained depending on the
failure mode. The control may not be maintained in the following case either: An error in an extension
base unit or in a module on an extension base unit is detected and causes a stop error of the control
system, system switching occurs, and a similar error is detected and causes a stop error of the
standby system (new control system). To ensure that the entire system operates safely even in these
cases, configure safety circuits external to the programmable controller.
[Precautions for using redundant function modules]
● The optical transmitter and receiver of the redundant function module use laser diodes (class 1 in
accordance with IEC 60825-1/JIS C6802). Do not look directly at a laser beam. Doing so may harm
your eyes.
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