Using the Electric VLSI Design System

Chapter III: HIERARCHY

| ## 2: Creating and Deleting Facets |

### Facet Creation

Facets are created with the Edit Facet... command of the Facets menu.

| A dialog of existing facets is presented. You can place the facet in the current window, or creating a new one. In addition, there are two options for filtering the list of facets. If there are cells with multiple versions, you can choose to see the old versions or ignore them. If there are facets from a "cell library", you can remove them from the list so that it only shows your design hierarchy.

To create a new facet, click on the "New Facet" button. This then presents a dialog in which the new facet name and its view can be specified. |

Facet names may not contain spaces, tabs, unprintable characters, or a colon. Uppercase and lowercase characters are not distinguished: The facet "UPPER" is the same as the facet "Upper." However, the form of capitalization that is used when a facet is first created is retained for all further use.

There are two ways to make a copy of a facet. The Duplicate Current Facet command of the Facets menu copies the facet in the current window to a new facet with a new cell name. You will be prompted for the new name. The New Version of Current Facet command also makes a copy of the facet in the current window. However, this copy is a "new version", which has the same cell name. The newly created facet is displayed in the window.

### Facet Deletion

To delete a facet, use the Delete Facet... command of the Facets menu. You will be given a list of facets and may select the one to delete.

When deleting a facet, there cannot be any instances of this facet, or the deletion fails. As a side effect of failure, you are shown a list of all other facets that have instances of this, so you can see the extent of its use. To find out whether a facet is being used elsewhere in the hierarchy, use the List Facet Usage... subcommand of the Facet Information command of the Facets menu.

Since Electric is able to keep old versions of facets, deleting the latest version will cause an older version to become the "most recent". Old versions are those whose facet names include the ";VERSION" clause indicating that there is a newer version of this view of the cell. For example, if you have facet "Adder" and an older version "Adder;1", then deleting "Adder" will cause "Adder;1" to be renamed to "Adder". This might make you think that the deletion failed, since there is still a facet called "Adder", but the older version will be gone.

To clean-up old and unused versions of facets, use the Delete Unused Old Versions command of the Facets menu. Any such facets that are no longer used as instances in other facets will be deleted from the library. You will get a list of deleted facets, and it is possible to undo this command.

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