When you place the first instance property of a part in a project, a copy of the part is created in the design cache. The design cache stores a copy of every part used in the design. (You can think of it as an embedded library.) All instances of the part normally refer to this copy in the design cache.
A cache part also retains a link to the library part on which it is based, so you can update or replace all of the parts in the design cache to synchronize them with the parts in the libraries.
The project manager updates the display of the design cache every time you open the cache. Just click on the design cache icon to close or open the design cache.
Using the Replace Cache and Update Cache commands
When you use the or the with the option to preserve schematic part properties, the part retains all instance and occurrence properties. This means you will not lose any changes made to pin properties after the part was placed, including those made by the Back Annotate or the Annotate tools.
The Replace Cache and Update Cache commands are quite similar. However, there are a few significant differences between the two commands.
You can modify a part's link to the library (part name, path, and library) with Replace Cache, but not with Update Cache. Update Cache only brings in new data when the path has not changed and part is modified in the library after placing it on schematic.
Another difference is that if the path and library names do not change, Replace Cache reloads the part definition into the design. However, if Update Cache finds that the part name and the library names are the same, it does not bring in part changes.
Replacing parts in a design
If you need to replace a part in your project, you could open the schematic page editor to find and delete each instance of the part, then place the replacement part. If your design includes many instances of this part, you can more easily achieve the same end with the .
Restoring parts in a design
When you delete a part, you also delete all of its properties. When you use the Replace Cache command to restore the part, the properties of the part instance are attached to the replacement part, but the pin properties are not restored.
You can also use the Replace Cache command if you want to undo edits to a part on a schematic page and restore the part's link to its library.
You would also use the Replace Cache command after you edit a part on a schematic page if you want to undo the edits and restore the part's link to its library.
When you delete a part, all of its properties are also deleted. When you use the Replace Cache command, properties of the part instance are attached to the replacement part; however, the pin properties are lost.
When you use the Update Cache command or the Replace Cache command with the option to preserve schematic part properties, all instance and occurrence properties of the schematic part are retained. This means you will not lose any changes made to pin properties after the part was placed, including those made by the Back Annotate or the Annotate tools.
To replace a part throughout a design
- From the design cache, select the part you want to replace.
- Choose Design – Replace Cache.
- In the dialog box that appears, enter the name of the replacement part and the library that contains it.
- Select the Replace schematic part properties action if you want to completely replace the part and its properties. Otherwise, use the default action to preserve schematic part properties.
- Click OK. When the project manager appears again, double-click on the design cache to verify that the replacement part is listed instead of the original part.
If you need to know a part's library of origin, you can select the part in the project manager, then select Replace Cache from the Design menu. The part name and the library and path are listed in the dialog box that appears. - Click Cancel to return to the project manager.
Following table provides an overview on Update Cache and Replace Cache commands:
Update Cache command | Replace Cache command | |||
|---|---|---|---|---|
| Preserve schematic properties | Replace schematic properties without preserve Refdes | Replace schematic properties with preserve Refdes | ||
| Part (Symbol) Graphics and Pins |
Updated | Updated | Updated | Updated |
| Part’s library level property values |
Updated if property edited on schematic. |
Updated if property edited on schematic. |
Updated | Updated |
|
Part’s schematic |
Preserved | Preserved | Updated | Updated |
| Part’s reference designator reference values |
Preserved | Preserved | Updated | Preserved |
| Pin properties values |
Updated if property value edited on schematic. |
Updated if property edited on schematic. |
Updated | Updated |
| Package Level properties values (such as PCB Footprint) |
Preserved | Preserved | Updated | Updated |
| Display location settings & coordinates for pin properties |
Updated | Updated | Updated | Updated |
| Display location settings & coordinates for part properties |
Preserved | Preserved | Updated | Updated |
When you use the Update Cache command or the Replace Cache command with the preserve schematic properties option on a part, same actions are performed.