Mike_RH said:
...does it really come down to personal preference?
To some degree, yes. But there are factors that should be weighed up before deciding which to use.
HMI tags - Pros...
Template applications can use HMI tags for relative ease of portability
You can implement folder structures for tag access
Use more descriptive tag names
Maintenance/Usability time will be reduced for editing
They have scaling, offset and retentive features
Tag value can be used to trigger alarms
Analog and Digital tags can have alarm conditions
HMI tags - Cons...
5000 tag creation limit
Tags must be resolved in the tag database before communicating with controller
HMI tag database must be exported/imported before a display can be used in another application
Initial tag loads are slow as the tags need to be cached
HMI tags are at a minimum 1 second slower than Direct Referenced tags for both read and write tag data updates (tag database must be accessed for both)
Extra tag description information consumes more memory
Retentive tags consume more memory
Each HMI tag used will typically consume 2.9KB of RAM
Direct Reference tags - Pros...
There is no Direct Reference tag creation limit
Direct Reference tags communicate directly with the controller and avoid the HMI tag database
Direct Reference tags are refreshed much quicker and can be used on displays that require increased performance
Direct Reference tags can be directly linked to objects on displays
Displays using only Direct Reference tags can easily be ported to applications with the same shortcut name
Each Direct Reference tag used will typically only consume 1.1KB of RAM
Direct Reference tags - Cons...
Less descriptive tag names
No tag folders available for structured tag access
No scaling, offset or retentive features - must be done in controller or module
Maintenance/Usability time is increased for edits
Mike_RH said:
...I prefer using the HMI database, as then if I need to make a change, there is only one to make...
One of the advantages of HMI tags is the Maintenance/Usability time saved because they facilitate a single point edit. This is probably why you prefer them.
Mike_RH said:
...My coworker prefers to directly reference the device when adding the object/animation on the screen...
One of the advantages of Direct Reference tags is that they can be assigned directly to objects on displays. This is probably why your co-worker prefers them.
So neither of you is really "right" or "wrong" in what you have chosen to use. Ye are using the best tag options to suit your given needs. But whether one should sway all one way or the other, is another matter. Depending on the application, you may need a mix of both, to some degree.
If you need to leverage the advantages that HMI tags provide, such as alarming, descriptive tag names and folders, retention, repeatability, etc., then chose them.
If you need to leverage the advantages that Direct Reference tags provide, such as quicker tag data updates, direct object linking, memory savings, etc., then chose them.
Regards,
George