Mitsubishi Electric MELSEC iQ-R Series User Manual page 4

[Design Precautions]
WARNING
● When connecting an external device with a CPU module or intelligent function module to modify data
of a running programmable controller, configure an interlock circuit in the program to ensure that the
entire system will always operate safely. For other forms of control (such as program modification,
parameter change, forced output, or operating status change) of a running programmable controller,
read the relevant manuals carefully and ensure that the operation is safe before proceeding. Improper
operation may damage machines or cause accidents.
● 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. Failure to do so may result in an
accident due to an incorrect output or malfunction.
● To maintain the safety of the programmable controller system against unauthorized access from
external devices via the network, take appropriate measures. To maintain the safety against
unauthorized access via the Internet, take measures such as installing a firewall.
[Design Precautions]
CAUTION
● Do not install the control lines or communication cables together with the main circuit lines or power
cables. Keep a distance of 150mm or more between them. Failure to do so may result in malfunction
due to noise.
● During control of an inductive load such as a lamp, heater, or solenoid valve, a large current
(approximately ten times greater than normal) may flow when the output is turned from off to on.
Therefore, use a module that has a sufficient current rating.
● After the CPU module is powered on or is reset, the time taken to enter the RUN status varies
depending on the system configuration, parameter settings, and/or program size. Design circuits so
that the entire system will always operate safely, regardless of the time.
● Do not power off the programmable controller or reset the CPU module while the settings are being
written. Doing so will make the data in the flash ROM and SD memory card undefined. The values
need to be set in the buffer memory and written to the flash ROM and SD memory card again. Doing
so also may cause malfunction or failure of the module.
● When changing the operating status of the CPU module from external devices (such as the remote
RUN/STOP functions), select "Do Not Open by Program" for "Opening Method" of "Module
Parameter". If "Open by Program" is selected, an execution of the remote STOP function causes the
communication line to close. Consequently, the CPU module cannot reopen the line, and external
devices cannot execute the remote RUN function.
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