Mitsubishi Q2ASCPU User Manual page 4

[DESIGN PRECAUTIONS]
(2) When the programmable controller detects the following error
conditions, it stops the operation and turn off all the outputs.
The overcurrent protection device or overvoltage protection device of
the power supply module is activated.
The programmable controller CPU detects an error such as a
watchdog timer error by the self-diagnostics function.
In the case of an error of a part such as an I/O control part that cannot
be detected by the programmable controller CPU, all the outputs may
turn on. In order to make all machines operate safely in such a case, set
up a fail-safe circuit or a specific mechanism outside the programmable
controller.
Refer to "LOADING AND INSTALLATION" in this manual for example
fail safe circuits.
(3) Depending on the failure of the output module's relay or transistor, the
output status may remain ON or OFF incorrectly. For output signals that
may lead to a serious accident, create an external monitoring circuit.
If load current more than the rating or overcurrent due to a short circuit
in the load has flowed in the output module for a long time, it may
cause a fire and smoke. Provide an external safety device such as a
fuse.
Design a circuit so that the external power will be supplied after
power-up of the programmable controller.
Activating the external power supply prior to the programmable
controller may result in an accident due to incorrect output or
malfunction.
For the operation status of each station at a communication error in
data link, refer to the respective data link manual.
The communication error may result in an accident due to incorrect
output or malfunction.
DANGER
A-2