• If you use fail-soft operation, write programming to determine whether Unit I/O data is valid. Without
such programming, the user program cannot distinguish between Units for which I/O refreshing is
continued and Units for which I/O refreshing is stopped.
Turning OFF the Power Supply
• Do not disconnect the cable or turn OFF the power supply to the Controller or a Slave Terminal
when downloading data or the user program from the Support Software.
• Always turn OFF the external power supply to the Units before attempting any of the following.
a)
Mounting or removing an NX Unit, Communications Coupler Unit, CPU Unit, Industrial PC, or
Communication Control Unit
b) Assembling Units
c) Setting DIP switches or rotary switches
d) Connecting or wiring cables
e) Attaching or removing terminal blocks or connectors
Units that supply power continue to supply power to the Units for up to several seconds after the
power supply is turned OFF. The PWR indicator remains lit as long as power is supplied. Confirm
that the PWR indicator is not lit before you perform any of the above.
Operation
• Confirm that the controlled system will not be adversely affected before you perform any of the fol-
lowing operations.
a) Changing the operating mode of the CPU Unit or Industrial PC (including changing the setting of
the Operating Mode at Startup)
b) Changing the user program or settings
c) Changing set values or present values
d) Forced refreshing
• Always suf
ficiently check the safety at the connected devices before you change the settings of a
slave or Unit.
General Communications
• Do not exceed the ranges that are given in the specifications for the communications distance and
number of connected Units.
• Refer to the user
’s manual for the Communications Coupler Unit for precautions for the safe use of
communications with the connected Communications Coupler Unit.
Unit Replacement
• When you replace a Unit, start operation only after you transfer the settings and variables that are
required for operation to the new Unit.
Precautions for Safe Use
23
NX-series System Units User's Manual (W523)
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