Omron NX-PA Series User Manual page 22

Precautions for Safe Use
Debugging
• Forced refreshing ignores the results of user program execution and refreshes I/O with the specified
values. If forced refreshing is used for inputs for which I/O refreshing is not supported, the inputs will
first take the specified values, but they will then be overwritten by the user program. This operation
differs from the force-set/reset functionality of the CJ-series PLCs.
• You cannot upload or download information for forced refreshing with the Sysmac Studio.
After downloading data that contains forced refreshing, change to RUN mode and then use the Sys-
mac Studio to perform the operation for forced refreshing.
Depending on the difference in the forced status, the control system may operate unexpectedly.
• Do not specify the same address for the AT specification for more than one variable.
Doing so would allow the same entity to be accessed with different variable names, which would
make the user program more difficult to understand and possibly cause programming mistakes.
General Communications
• When you use data link communications, check the error information that is given in _ErrSta (Control-
ler Error Status) to make sure that no error has occurred in the source device. Create a user program
that uses reception data only when there is no error in the source device. If there is an error in the
source device, the data for the data link may contain incorrect values.
• Unexpected operation may result if inappropriate data link tables are set. Even if appropriate data link
tables have been set, confirm that the controlled system will not be adversely affected before you
transfer the data link tables. The data links start automatically after the data link tables are trans-
ferred.
EtherNet/IP Communications
• Make sure that the communications distance, number of nodes connected, and method of connec-
tion for EtherNet/IP are within specifications.
Do not connect EtherNet/IP communications to EtherCAT or other networks. An overload may cause
the network to fail or malfunction.
• All related EtherNet/IP nodes are reset when you transfer settings for the built-in EtherNet/IP port
(including IP addresses and tag data links settings). The settings can only be enabled after the reset.
Confirm that the system will not be adversely affected by resetting nodes before you transfer the set-
tings.
• If EtherNet/IP tag data links (cyclic communications) are used with a repeating hub, the communica-
tions load on the network will increase. This will increase collisions and may prevent stable communi-
cations. Do not use repeating hubs on networks where tag data links are used. Use an Ethernet
switch instead.
• When you use two EtherNet/IP networks separately, provide separate hubs to connect nodes in each
network.
• Be careful not to mix nodes that belong different EtherNet/IP networks when you connect them.
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NX-series CPU Unit Hardware User's Manual (W535)