Rockwell Automation Logix5000 Controllers I/O and Tag Data Programming Manual - Manual (Page 64)

Chapter 4 Data access control
• FactoryTalk Historian software.
• Other third-party software.
You configure external access from a menu when you create a new tag or data type.
You can also change that value just like other tag attributes. You can make these
changes throughout the application. For example, you can make the changes in the
User-defined Data Type Editor, New Tag dialog box, and the Tag Properties
dialog box.
External Access Settings Description
Read/Write External applications and devices have full access to the tag and can read and
change the tag’s value.
Read Only External applications can read, but cannot change, the tag’s value.
None External applications cannot read or change the tag’s value.
Important: • The Logix Designer application has full access to all tags, regardless of their external access settings.
External access applies to all program, controller, and Add-On Instruction scoped tags.
• If the controller is in safety locked mode, only the safety tags are disabled from being accessed. The
standard tags have the same behavior as in the unlocked mode.
External access options
You can choose one of three options: Read/Write, Read Only, or None from the
External Access list on the following Logix Designer dialog boxes.
• New Tag (See Configure external access in the New Tag dialog box on page
65 )
• Tag Properties (See Set up external access in the Tag Properties dialog box
on page 67 )
The default value in the External Access list depends on the usage and type of the
tag. The following table describes the values.
If the tag is Default value is
Alias Same as its target. See Important note following this table.
Controller or program scoped and equipment
phase input parameters
The initial value is Read/Write.
Thereafter, when you create a new tag, the default external access tag
keeps the value of your previous choice. (1)
Equipment phase output parameters The initial value is Read Only.
Thereafter, when you create a new tag, the default external access tag
keeps the value of your previous choice. (1)
(1) The external access default value for tag creation is stored for each Windows login account.
Configure external access
64 Rockwell Automation Publication 1756-PM004E-EN-P - October 2014