72 Rockwell Automation Publication 1756-PM004D-EN-P - September 2012
Chapter 4 Data Access Control
External Access Availability
The following table describes the conditions in which the External Access box is
disabled.
The External Access box is always disabled for any tag whose data type is Alarm
Analog or Alarm Digital. The external access status is always Read/Write for these
data types.
Dialog Box/Window Considerations
New Tag The External Access box is disabled if:
• the tag is an alias tag.
• the controller is user locked online.
If you change the Type box from Base to Alias, the External Access box becomes
disabled and appears blank. If you choose a target for an alias tag in the Alias For box,
the External Access box remains disabled and the external access value appears in the
External Access box.
The external access setting of an alias tag can only be changed through its base tag.
Tag Properties The External Access box is disabled if:
• you do not have permission to change the external access settings.
• the redundancy controller is in any state that does not allow changes.
• the controller is user-locked online from another computer.
• the controller is safety-locked and the tag is a safety tag.
• the Scope is an equipment phase and the equipment phase feature is not
activated in the current license.
• the tag is an alias tag.
• the controller is in hard-run mode.
Tag Editor The External Access box is disabled if:
• you do not have permission to change the external access settings.
• the redundancy controller is in any state that does not allow changes.
• the controller is user-locked online.
• the controller is safety-locked and the tag is a safety tag. Only the safety tags’
External Access cell is disabled.
• the Scope is an equipment phase and the equipment phase feature is not
activated in the current license.
• the tag is an alias tag.
• the controller is in hard-run mode.
• the row represents an expanded array dimension, bit, or data member.
For tags of Predefined (Atomic and Structural), Module-defined Data Types and
String, all of these tag members will have the same external access level because:
• they are all hard-coded to ‘Read/Write’ and you can only view, not change, this
value. You also cannot change external access for the data type members.
• an external access change on the tag results in an update on all tag members.
For Array tags, all elements:
• must have the same external access level.
• of all data members for predefined or module-defined data types will have the
same external access setting.
• of each data member for user-defined type (UDT) and Add-On Instruction will
have the more restrictive external access setting between the element external
access setting and the external access setting of the member in the type
definition.
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