Selectively annotating reference designators can be a time consuming task. In OrCAD Capture’s new version 16.6, a feature has been introduced to tell the automated annotation utility that a schematic part has a reference designator that needs to remain unchanged throughout the annotation process.
Let’s take a look at a scenario where this may pop up in your design work:
One situation this feature can be very useful in is when you’ve already netlisted your schematic off to the board and don’t have the luxury of doing a blanket change on all your reference designators anymore. When you’re in this situation, you have got to keep the reference designators the same for the parts on your schematic that correspond to existing parts on your board but you’d like to have the automated annotation tool annotate some additional parts that you’ve placed since you last netlisted.
Previous to V16.6, you really only had two netlisting options: Incremental Reference Update orUnconditional Reference Update.
Incremental Reference Update would give a new reference designator number to any part that had a ? in the ref des field (eg. R?, C?, U?). Unconditional Reference Update resets all the reference designators to ? then proceeds to re-annotate the entire design. The Unconditional Reference Update is very useful when you’re not too concerned with what your reference designators are but once you have some that should remain unchanged, you really can’t use it anymore (in versions prior to 16.6).
Now, in 16.6 you have the ability to select a single part or collection of parts and Right Mouse Button (RMB) on them and choose User Assigned Reference > Set.
Alternatively, you can also set the flag by going to the part in the Property Editor, RMB on the value of the Reference property and choose User Assigned Reference > Set
This will let the tool know that the value of this reference designator is one that you would like it to keep throughout the annotation process. Once this flag has been set, you will see graphical proof on the schematic with a line under the reference designator of the part you set.
Note that this User Assigned Reference flag will be set automatically if the:
- reference designator is changed in the property editor
- reference designator is changed from the schematic canvas
- reference designator is changed in board and then back annotated
If you wish to unset the flag, you can RMB > User Assigned Reference > Unset. This works for one or many parts selected at once.
If you have some parts that have the User Assigned Reference set, you can now run anUnconditional Reference Update (Tools > Annotate) but pass over these specifically flagged parts by selecting the “Preserve User Assigned Valid References” option at the bottom.
When that option is selected, even though the Action you’ve selected is Unconditional Reference Update, the parts that have Reference Designators that are flagged as User Defined will remain unchanged after the annotation is complete. You will get a warning in the session log that the reference designator has not been changed by the annotation process:
WARNING(ORCAP-2349): Reference of 'R2(Value 150) on page PAGE1' is User Edited. It will not be annotated
I hope that this shows you why there can be reference designators in your designs that are underlined and how to annotate your designs more effectively using the new preserve feature in 16.6