Mitsubishi Electric MELSEC iQ-R Series User Manual page 5

[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. When a Safety CPU is used, data cannot be
modified while the Safety CPU is in SAFETY MODE.
● 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. For areas used for safety communications, they are protected from being written by
users, and thus safety communications failure caused by data writing does not occur.
● 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. When safety communications are used, an interlock
by the safety station interlock function protects the system from an incorrect output or malfunction.
● Configure safety circuits external to the programmable controller to ensure that the entire system
operates safely even when a fault occurs in the external power supply or the programmable controller.
Failure to do so may result in an accident due to an incorrect output or malfunction.
(1) Machine OPR (Original Point Return) is controlled by two kinds of data: an OPR direction and an
OPR speed. Deceleration starts when the near-point dog signal turns on. If an incorrect OPR
direction is set, motion control may continue without deceleration. To prevent machine damage
caused by this, configure an interlock circuit external to the programmable controller.
(2) When the positioning module detects an error, the motion slows down and stops or the motion
suddenly stops, depending on the stop group setting in parameter. Set the parameter to meet the
specifications of a positioning control system. In addition, set the OPR parameter and positioning
data within the specified setting range.
(3) Outputs may remain on or off, or become undefined due to a failure of a component such as an
insulation element and transistor in an output circuit, where the positioning module cannot detect
any error. In a system that the incorrect output could cause a serious accident, configure an
external circuit for monitoring output signals.
● If safety standards (ex., robot safety rules, etc.,) apply to the system using the module, drive unit, and
servo motor, make sure that the safety standards are satisfied.
● Construct a safety circuit externally of the module or drive unit if the abnormal operation of the module
or drive unit differs from the safety directive operation in the system.
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