Using Electric 3-4: Examining Instances

Chapter 3: HIERARCHY

| ## 3-4: Examining Instances |

When instances are initially created, they are drawn as black boxes with nothing inside. This form of instance display is called unexpanded, as opposed to expanded display which shows the actual layout inside the instance. To expand an instance, select it and use the subcommands of the Expand Facet Instances command of the Facets menu. The One Level Down subcommand opens up the next closed level; the All the Way subcommand opens up all levels to the bottom; and the Specified Amount... lets you type a number of levels of hierarchy to expand. These commands expand all highlighted facets. If a highlighted facet is already expanded, this command expands any subfacets inside of the instance, repeatedly down the hierarchy.

Once expanded, a facet instance will continue to be drawn with its contents shown until the subcommands of the Unexpand Facet Instances command are used. These commands return facet instances to their black-box form, starting with the deepest subfacets that are expanded at the bottom of the hierarchy. The One Level Up subcommand closes up the bottommost expanded level; the All the Way subcommand closes all levels from the bottom; and the Specified Amount... lets you type a number of levels of hierarchy to close.

The expansion information can also be set or reset by using the Get Info command of the Info menu and clicking on the "Expanded" or "Unexpanded" buttons.

There are times when you want to see the layout inside of a facet instance, but only temporarily. The Look Inside Highlighted command of the Facets menu displays everything in the highlighted area, down through all hierarchical levels. This is a one-shot display that reverts to unexpanded form if the window is shifted, scaled, or redrawn.

There is a slight difference in specification between the Expand Facet Instances subcommands and the Look Inside Highlighted command. The Expand Facet Instances subcommands affect facet instances only, and thus any instances that are highlighted or in the highlighted area will be completely expanded. The Look Inside Highlighted command affects layout display in an area, so only those parts of instances that are inside of the highlighted area will be shown. Thus, the command Look Inside Highlighted is more precise in what it expands and can be used, in conjunction with the rectangle select button, to show only a specific part of the circuit.

Examining facet instances can be quite time consuming, especially if you are looking at an entire chip, fully flattened. To avoid delays, Electric simplifies the display of facets when the scale grows too tiny. These tiny facets get "hashed-out" rather than fully drawn. See Section 3-7 for more information.

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