Mitsubishi Q00JCPU User Manual page 4

[Design Precautions]
Install a safety circuit external to the PLC that keeps the entire system safe even when there are
problems with the external power supply or the PLC module. Otherwise, trouble could result from
erroneous output or erroneous operation.
(1) Outside the PLC, construct mechanical damage preventing interlock circuits such as emergency
stop, protective circuits, positioning upper and lower limits switches and interlocking forward/
reverse operations.
(2) When the PLC detects the following problems,
it will stop calculation and turn off all output in the case of (a).
In the case of (b), it will hold or turn off all output according to the parameter setting.
Note that the AnS series module will turn off the output in either of cases (a) and (b).
(a) The power supply module has
over currentprotection equipment
and over voltage protection
equipment.
(b) The CPU module self-diagnosis
functions, such as the watchdog
timer error, detect problems.
In addition, all output will be turned on when there are problems that the PLC CPU cannot
detect, such as in the I/O controller. Build a fail safe circuit exterior to the PLC that will make sure
the equipment operates safely at such times.
Refer to " LOADING AND INSTALLATION" in QCPU User's Manual (Hardware Design,
Maintenance and Inspection) for example fail safe circuits.
(3) Output could be left on or off when there is trouble in the outputs module relay or transistor. So
build an external monitoring circuit that will monitor any single outputs that could cause serious
trouble.
A
- 2
DANGER
Q series module
Output OFF
Hold or turn off all
output according to
the parameter setting.
AnS series module
Output OFF
Output OFF