Chapter 3: Hierarchy
3-2: Cell Creation and Deletion

Figure 3.1
Cells are created with the New Cell... command (in menu Cell).

The New Cell... command requests a new cell name as well as its view and technology. You can choose to show the cell in the current window, or create a new one.

Cell names may not contain spaces, tabs, curly braces, semicolons, unprintable characters, or a colon.

Another way to create a new cell is to make a copy of an existing one. The Duplicate Current Cell... and Duplicate Cell... commands (in menu Cell) copy a cell to a different one with a new name (you will be prompted for the new name). The New Version of Current Cell command makes a copy of the cell in the current window, but since it is a "new version", it has the same cell name. The newly created cell is displayed in the window.

Once cells are created you can edit them with the Edit Cell... command (in menu Cell). Cells can also be edited by using the cell explorer (see Section 4-5-2 for more).

To delete a cell, use the Delete Cell... command (in menu Cell). When deleting a cell, there cannot be any instances of this cell, or the deletion fails. As a side effect of failure, you are shown a list of all other cells that have instances of this, so you can see the extent of its use. To find out whether a cell is being used elsewhere in the hierarchy, use the List Cell Usage command (in menu Cell / Cell Info). For an explanation of the "Evaluate Numbers when Sorting Names" checkbox, see Section 3-7-1.

Because Electric is able to keep old versions of cells, deleting the latest version will cause an older version to become the "most recent". Old versions are those whose cell names include the ";VERSION" clause indicating that there is a newer version of this view of the cell.

Figure 3.11

For example, if you have cell "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, because there is still a cell called "Adder", but this cell is actually the older (but now most recent) version.

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

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