Mitsubishi Electric RJ72GF15-T2 User Manual page 5

[Design Precautions]
WARNING
● 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.
● Configure safety circuits external to the remote head module to ensure that the entire system
operates safely even when a fault occurs in the external power supply or the remote head module.
Failure to do so may result in an accident due to an incorrect output or malfunction.
(1) Emergency stop circuits, protection circuits, and protective interlock circuits for conflicting
operations (such as forward/reverse rotations or upper/lower limit positioning) must be configured
external to the remote head module.
(2) When the remote head module detects an abnormal condition, outputs are:
• Held or turned off according to the parameter setting of each module mounted on the main
base unit or extension base unit if the self-diagnostic function of the remote head module
detects an error such as a watchdog timer error.
(3) All outputs may be turned on if an error occurs in a part, such as an I/O control part, where the
remote head module cannot detect any error. To ensure safety operation in such a case, provide a
safety mechanism or a fail-safe circuit external to the remote head module. For a fail-safe circuit
example, refer to "General Safety Requirements" in the MELSEC iQ-R Module Configuration
Manual.
● Configure a circuit so that the remote head module is turned on first and then the external power
supply. If the external power supply is turned on first, an accident may occur due to an incorrect output
or malfunction.
● When connecting an external device with a remote head module to modify data of a running remote
head module, configure an interlock circuit in the program of the master station to ensure that the
entire system will always operate safely. For other forms of control (such as parameter change, forced
output, or operating status change) of a running remote head module, 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 head module is remotely controlled by an external device, immediate
action cannot be taken if a problem occurs in the remote head module due to a communication failure.
To prevent this, configure an interlock circuit in the program of the master station, and determine
corrective actions to be taken between the external device and remote head module in case of a
communication failure.
● Do not write any data to the buffer memory in the remote head module. Doing so may cause
malfunction of the programmable controller system.
● Do not write any data from the remote head module to the "system area" and "write-protect area" of
the buffer memory in each module. Also, do not use any "use prohibited" signals as an output signal
from the remote head 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.
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