Chapter III: HIERARCHY

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Examining Instances

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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 Expand Facet Instances command of the Facets menu. This command expands 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 Unexpand Facet Instances command is used. This command returns facet instances to their black-box form, starting with the deepest subfacets that are expanded at the bottom of the hierarchy.

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 and the Look Inside Highlighted commands. The Expand Facet Instances command affects 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, and thus 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.


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