A-6
Precautions When Accessing Exter-
nal Outputs in CPU Units
Observe the following precautions when you access variables or I/O memory addresses that are as-
signed to external outputs in an NJ/NX-series CPU Unit.
Precaution on Writing from External Devices, Variables That Are Assigned
to External Outputs
Any value that is written to a variable that is assigned to an external output in an NJ/NX-series CPU
Unit through a tag data link or communications instruction will be overwritten by the execution re-
sults of the user program.
The value that is written from the tag data link or communications instruction will therefore not be
output to the external device.
The following types of variable are assigned to the external outputs.
CPU Unit Common
• The device variables (or global variables) that are assigned to an I/O port of an EtherCAT output
slave
NJ-series CPU Unit
• The devices variables (or global variables) that are assigned to an I/O port of a CJ-series Basic
Output Unit
• The global variables with AT specifications to output bits that are assigned to CJ-series Basic
Output Units
NX102 CPU Unit and NX1P2 CPU Unit
• The global variables with AT specifications to the memory used for CJ-series Units, of which Net-
work Publish attributes are set to output
Precaution When Directly Writing to I/O Memory Addresses Assigned to
Output Bits for CJ-series Basic Output Units
Any value that is written to an I/O memory address that corresponds to an output bit that is as-
signed to a CJ-series Basic Output Unit through a tag data link will be overwritten by the execution
results of the user program.
The value that is written directly to the I/O memory address from the tag data link will therefore not
be output to the external device.
Appendices
A-59
NJ/NX-series CPU Unit Built-in EtherNet/IP Port User’s Manual (W506)
A-6 Precautions When Accessing External Outputs in CPU Units
A
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