Mitsubishi Electric MELSEC iQ-RX40NC6B User Manual page 5

I/o module (with diagnostic functions)

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[Design Precautions]

WARNING

● 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.

[Precautions for using the I/O module with diagnostic functions in normal mode]

● Configure a circuit so that the programmable controller 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.

[Precautions for using the I/O module with diagnostic functions in SIL2 mode]

● When the I/O module with diagnostic functions detects a fault in the external power supply or

programmable controller, it turns off outputs. Configure an external circuit to ensure that the power

source of a hazard is shut off by turning off the outputs. Failure to do so may result in an accident.

● When a load current exceeding the rated current or an overcurrent caused by a load short-circuit

flows, the output module with diagnostic functions detects an error and turns off all outputs. Note that

if the overcurrent state continues for a long time, it may cause smoke and fire. To prevent this,

configure an external safety circuit, such as a fuse.

● Configure protection circuits, such as a fuse and breaker, external to the output module with

diagnostic functions.

● When a communication failure (data link) occurs in CC-Link IE Field Network, the I/O module with

diagnostic functions turns off outputs. However, the program does not automatically turn off outputs.

Create a program that turns off outputs when a communication failure (data link) is detected in CC-

Link IE Field Network. If data link is restored with outputs on, connected machines may suddenly

operate, resulting in an accident.

● Create an interlock program which uses reset buttons so that the system does not restart

automatically after executing safety functions and turning off outputs.

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