Rockwell Automation Logix5000 Controllers I/O and Tag Data Programming Manual - Manual (Page 76)

Chapter 4 Data access control
Only tags with external access settings of Read/Write or Read Only can be
mapped to a PLC-2 controller and PLC-5/SLC controllers.
1. In the PLC-2 or PLC-5/SLC Mapping dialog box, type a file number.
2. Choose a tag from the Name list. Only eligible tags that are set to either
Read/Write or Read Only appear in the menu.
If you manually type the name of a tag whose external access is set to None,
an error message appears.
3. Click OK.
The Logix Designer application preforms a check to verify an imported program
file has a valid external access value. A default value is assigned to unspecified tags
that are imported from programs created in the Logix Designer application earlier
than version 18.
An error message appears in the Logix Designer application for imported files that
contain tags with any value other than Read/Write, Read Only, and None.
Object Name Default External Access
Controller and program-scoped standard tags Read/Write
All safety tags( Read Only
Add-on Instruction local tags Read/Write
Add-on Instruction Input parameters Read/Write
Add-on Instruction Output, EnableIn and EnableOut parameters Read Only
Add-on Instruction InOut parameters N/A
Equipment phase output parameters Read Only
Members of all data types Read/Write
In version 18 and later of the Logix Designer application, you can designate tags as
constants to protect them from being changed programmatically by:
• The controller programming application.
• Logic in the controller.
The tags that you cannot designate as constants are User-defined type members,
Add-On Instruction input and output parameters, and local tags. You make a tag a
constant value tag by selecting the Constant check box on tag creation dialog
boxes and tag editor/monitor windows.
Tag mapping
considerations
Imported tag behavior
Constant value tags
76 Rockwell Automation Publication 1756-PM004E-EN-P - October 2014