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Troubleshooting Problems with Unit Versions on the CX-Programmer
Problem Cause Solution
After the above message is displayed, a compiling 
error will be displayed on the Compile Tab Page in the 
Output Window.
An attempt was made using CX-
Programmer version 4.0 or higher 
to download a program contain-
ing instructions supported only by 
CPU Units Ver. 2.0 or later to a 
Pre-Ver. 2.0 CPU Units.
Check the program or change 
the CPU Unit being down-
loaded to a CPU Unit Ver. 2.0 
or later.
An attempt was made using CX-
Programmer version 4.0 or higher 
to download a PLC Setup con-
taining settings supported only by 
CPU Units Ver. 2.0 or later (i.e., 
not set to their default values) to a 
Pre-Ver. 2.0 CPU Units.
Check the settings in the PLC 
Setup or change the CPU Unit 
being downloaded to a CPU 
Unit Ver. 2.0 or later.
“????” is displayed in a program transferred from the 
PLC to the CX-Programmer. 
CX-Programmer version 3.3 or 
lower was used to upload a pro-
gram containing instructions sup-
ported only by CPU Units Ver. 2.0 
or later from a CPU Unit Ver. 2.0 
or later.
The new instructions cannot 
be uploaded using CX-Pro-
grammer version 3.3 or lower. 
Use CX-Programmer version 
4.0 or higher.