Precautions for Safe Use
20
NX-series Digital I/O Unit User’s Manual (W521)
• When you set the Operating Mode at Startup, confirm that no adverse effect will occur in the system.
• Before you start operation, always register the NX Units that are connected to the Communications
Coupler Unit in the host communications master as the Unit Configuration Information.
• Check the user program, data, and parameter settings for proper execution before you use them for
actual operation.
• If you change the fail-soft operation setting, the output status when the error occurs may also change.
Confirm safety before you change the fail-soft operation setting.
• 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.
• 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.
Mounting or removing an NX Unit, Communications Coupler Unit, CPU Unit, or Industrial PC
Assembling Units
Setting DIP switches or rotary switches
Connecting or wiring cables
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.
• Confirm that the controlled system will not be adversely affected before you perform any of the fol-
lowing operations.
Changing the operating mode of the CPU Unit or the Industrial PC (including changing the setting
of the Operating Mode at Startup)
Changing the user program or settings
Changing set values or present values
Forced refreshing
• Always sufficiently check the safety at the connected devices before you change the settings of a
slave or Unit.
• 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.
Turning ON the Power Supply
Actual Operation
Turning OFF the Power Supply
Operation
General Communications
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