
A - 2
[DESIGN PRECAUTIONS]
!
DANGER
When overcurrent which exceeds the rating or caused by short-circuited load flows in the output
module for a long time, it may cause smoke or fire. To prevent this, configure an external safety
circuit, such as fuse.
Build a circuit that turns on the external power supply when the PLC main module power is
turned on. If the external power supply is turned on first, it could result in erroneous output or
erroneous operation.
When a data link results in a communication error, the faulty station changes in operating status
depending on the used data link type.
(1) For the data link data, the data prior to the communication error will be held.
(2) The MELSECNET (II,/B,/10) remote I/O station will turn all output off.
(3) The MELSECNET/MINI-S3 remote I/O station will hold the output or turn all output off
depending on the E.C. remote setting.
Refer to the data link manuals regarding the method for setting the communication problem
station and the operation status when there are communication problem.
When connecting a peripheral device to the CPU module or connecting a personal computer or
the like to the intelligent function module to exercise control (data change) on the running PLC,
configure up an interlock circuit in the sequence program to ensure that the whole system will
always operate safely.
Also before exercising other control (program change, operating status change (status control))
on the running PLC, read the manual carefully and fully confirm safety.
Especially for the above control on the remote PLC from an external device, an immediate
action may not be taken for PLC trouble due to a data communication fault.
In addition to configuring up the interlock circuit in the sequence program, corrective and other
actions to be taken as a system for the occurrence of a data communication fault should be
predetermined between the external device and PLC CPU.
When configuring a system, do not leave any slots vacant on the base. Should there be any
vacant slots, always use a blank cover (A1SG60) or dummy module (A1SG62).
When the extension base A1S52B, A1S55B or A1S58B is used, attach the dustproof cover
supplied with the product to the module installed in slot 0.
If the cover is not attached, the module's internal parts may be dispersed when a short-circuit
test is performed or overcurrent/overvoltage is accidentally applied to the external I/O area.
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