Design Precautions - Mitsubishi Electric QJ71GF11-T2 User Manual

[Design Precautions]

● When connecting GX Works2 with the CPU module or connecting a personal computer with an
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 or operating status change) of a running
programmable controller, read the relevant manuals carefully and ensure that the operation is safe
before proceeding. 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.
● For the operating status of each station after a communication failure, refer to Page 140, Section
8.1.7 in this manual. Incorrect output or malfunction due to a communication failure may result in an
accident.
● Do not write any data to the "system area" of the buffer memory in the intelligent function module.
Also, do not use any "use prohibited" signals as an output signal from the CPU module to the
intelligent function module.
Doing so may cause malfunction of the programmable controller system.
● To set a refresh device in the network parameter, select the device Y for the remote output (RY)
refresh device. If a device other than Y, such as M and L, is selected, the CPU module holds the
device status even after its status is changed to STOP.
● 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.
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WARNING