Emerson Exchange 365

You are not misunderstanding things. The unassigned I/O reference list is a list of Tags entered into control modules that are not assigned to an IO channel. This allows you to bind an IO channel to a tag name while defining the control module, but you have not configured the IO where this signal will actually exist. The only way to add a tag to the Unassigned IO Reference list is to configure that tag name into a control module IO reference. The tag will disappear from the list if you assign it or go back in the control module and remove it.

Some times, it takes a few minutes for a tag to appear in the list. Not sure how long you waited, but it should make it to the list. If you have not cleaned the database for a while, (regular maintenance stuff), it might help to do so.

For those not familiar with the Unassigned IO references, it is good to understand the perspective of this list.
- Device Tags are "Assigned" to IO channels. A Device Tag can be created in a control module by typing in the tag, or via bulk Import. If the Device Tag is not yet defined at the IO channel level, it is added to the Unassigned IO list. The Device Tag is referenced by the Module, but is Unassigned.

- An IO channel is "Referenced" by a Module using its Device Tag. It can get confusing because we are asked to "assign" a CHARM IO channel to a controller, but this has nothing to do with which modules reference the IO Signal. The IO Configuration tool lists all IO channels by hardware location and indicates the Device Tag of the channel, and what module(s) it is "Referenced By". If the Referenced By field is blank, no module currently references this channel, by its Device Tag.

So Device Tags are Assigned to IO channels, IO channels are referenced by Control modules. You can create Device Tags during Control Module creation, in which case they are referenced, but not yet assigned. Or you can create the Device Tag when defining the IO Channel, at which point they are Assigned, but not yet Referenced. Late binding happens when both the tag is assigned, and is referenced. This allows the IO to be configured, installed and even commissioned, waiting to be referenced. When the referencing module is imported/added to the database the IO channel is bound by tag to that module reference. The control module configuration Engineer does not need to know where the IO channel is physically located. The tag binding will connect the two.

Note that a control module can reference an IO channel assigned to a different controller. Since the IO channel is not local to the module's controller, the input value is passed by it's host controller to the Module's host controller. In this way, a single IO channel can be referenced from different modules in different controllers. Prior to v12.3, multiple modules referencing a single IO channel would result in multiple DST licenses. In v12 and later, each IO referenced by one or more modules is counted as a single DST license.

Andre Dicaire