Using the Electric VLSI Design System

Chapter III: HIERARCHY

| ## 7: Facet Information |

### Miscellaneous Commands

The most basic facet information that you can get is a list of facets. This can be done with the Edit Facet... command of the Facets menu. The dialog will show the facet names (at which point you can cancel the dialog).

For more facet information, use the Facet Information submenu of the Facets menu. To get some basic information about the current facet (size, dates, etc) use the Describe this Facet subcommand. To see a more complete list of facets, with creation and revision dates, use the Describe all Facets command. This same information can be written to a disk file, formatted for spreadsheets (tab-separated) with the Describe all Facets to File... command. In this extended view, the last five columns show the usage (the number of times that this facet appears as an instance in other facets), and four state bits: L (if the facet contents are locked), I (if instances of the facet are locked), C (if the facet is part of a cell library), and D (if the facet has passed design-rule checking).

To see a list of facet instances below the current facet, use the List Facet Instances command. To look up the hierarchy and find facets that contain the current facet as an instance, use the List Facet Usage... command.

To see which ports have been exported from the current facet, use the Info menu commands List Exported Ports (for a text listing) or Show Exported Ports (for a graphical indication). To see a list of exported ports that are electrically connected to the current object, at all levels of hierarchy, use List Ports on Network command.

The most advanced command for examining hierarchical structure is Show Facets Graphically (of the Info menu) which creates a graph of the facet hierarchy. This graph is actually a new facet, called "FacetStructure", built from Artwork nodes, and stored with the other facets. If you select a name in this graph, then the Edit Facet... command of the Facets menu defaults to that facet.

The Edit Documentation View command of the View menu allows you to store arbitrary text with the cell. The text editing window that appears can contain any information. See section 4-10 for more on text editing.

### Facet Options

To examine and set more information about existing facets, use the Facet Options... command of the Facets menu:

The upper part of the dialog provides options on a per-facet basis (choose the facet and set its options). The checkbox "Disallow modification of anything in this facet", allows you to control whether the contents of a facet is editable or not. When the modification is disallowed, no changes may be made. This is useful when you want to allow examination without accidental modification. The checkbox "Disallow modification of instances in this facet", is also prevents changes to the selected facet, but in this case, only sub-instances are locked. This is useful when you have a correct instance placement and are doing wiring. Buttons on the right allow you to set or clear these flags for all facets.

If you make a change that has been disallowed, a dialog appears that asks if you want to override the lock. You may make the change, disallow the change, or remove the lock (which effectively unchecks the locks in the Facet Options... dialog). |

The check box "Part of a cell-library" indicates that this facet is from a library of standard cells and should be treated accordingly. Buttons on the right allow you to set or clear this flag for all facets. Most dialogs that list facets can remove those from cell-libraries to keep the list simpler.

The "Expand new instances" and "Unexpand new instances" buttons choose whether newly created instances of this facet are expanded (contents visible) or unexpanded (drawn with a black outline).

The "Characteristic Spacing" is the spacing of this facet when arrayed (see section 6-4).

The lower part of the dialog contains options that will apply to all facets. The checkbox "Disallow modification of facet instances" requests that all facet instances be anchored. Any command that results in the movement of a facet instance will fail. This is useful when a large circuit is being assembled, for it is often the case that there are many facet instances that must be wired together. It is common during this phase of design to accidentally create, delete, move, or otherwise alter the facets, which causes an annoying delay in editing. This checkbox prevents the placement from being affected by wire editing commands. Wires may still be created, and primitives may still be fully edited, but any attempt to manipulate facet instances results in an error.

The check box "Tiny facets hashed out" requests that facets be displayed with a gray hash pattern when they are too tiny for their contents to be distinguished. Without this option, all geometry is drawn, which can take a long time. You can control the threshold of "tinyness" by setting the number of lambda units per pixel. Any view in which this many lambda units are shown in pixel will be too small to display fully.

The check box "Check facet dates during creation" requests that date information be used to ensure a proper circuit building sequence. When this box is checked, warning messages will be issued when editing a facet that has more recent subfacet instances. Electric tracks facet creation and revision dates, and this information can be displayed with the Describe all Facets subcommand of the Facet Information command of the Facets menu.

### The Facet Explorer

| The Facet Explorer... command of the Facets menu splits the current window, and shows a hierarchical "explorer" window in the left half. Each library is shown, and inside of it are the "top level" facets (top level facets are those that are not used as instances in any other facets). By clicking on the box with the "+", the facet's contents are shown in a recursively indented manner. Each facet lists the number of times that it occurs in the higher-level facet. Besides simply seeing the hierarchy of your circuit, there are special controls that can be done in the Facet Explorer. To view any facet, simply double-click on its name. To delete a facet, click on its name and hit the DELETE key. To make a library the current library, double-click on its name. The line which separates the Facet Explorer from the edit window can be moved simply by clicking on it and dragging it (see section 4-3 for more on window control). To make the Facet Explorer go away, delete that window partition, or issue the Facet Explorer... command again.

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