Mitsubishi MELSEC-Q Series User Manual page 3

[Design Precautions]
DANGER
When controlling a running programmable controller (e.g. data modification),
create an interlock circuit on sequence programs so that the whole system
functions safely all the time.
Also, be sure to read the manual carefully and ensure safety before
performing any other controls such as operating status change.
Especially, when controlling a programmable controller from a remote
location via network, problems on the programmable controller side may not
be dealt with promptly due to failure of data communications.
Create an interlock circuit on a sequence program.
For the operation status of each station at a communication error, refer to the
manual for that station.
Incorrect output or malfunctions may cause an accident.
Install a safety circuit external to the programmable controller that keeps the
entire system safe even when there are problems with the external power
supply or the programmable controller.
Otherwise, trouble could result from erroneous output or erroneous
operation.
When the programmable controller system security needs to be protected
against illegal access from an external device via a network, take measures
at the user's discretion.
Do not write any data to the "System area" in the buffer memory of the
intelligent function module.
As for signals output from the programmable controller CPU to the intelligent
function module, never output (ON) a "Use prohibited" signal.
Doing these operations may cause malfunctions of the programmable
controller system.
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