Transparent Layout Hierarchy Generation

Transparent layout hierarchy is the layout hierarchy other than the top-level hierarchy, which does not match the schematic hierarchy, but the binder can still bind to the instances within it. You can think of transparent instances as instances that the binder can “see through”. This means the binder does not consider the transparent instances as leaf-level instances and can bind to the instances and nets within.

You may choose to introduce a transparent layout hierarchy in your design to expedite layout design when using design styles such as half-cells. Alternatively, you can introduce a transparent layout hierarchy in a design and reuse the layout within the same design or in another design.

Layout XL does not support automatic layout generation (Generate All From Source) when descended into a transparent instance master but automatic updates to rectify any connectivity, parameter, and master mismatches with the source are supported via the Update Components And Nets command. In addition, interactive commands such as interactive chaining and folding are supported and so are the manual edits within a descended transparent instance master. The Check Against Source command can be used to report any mismatches with the source and the Navigator assistant gets interactively updated to reflect the correct binding status of the edited instances.

Likewise, the Define Device Correspondence form accurately updates the schematic and the layout trees when you descend into the transparent hierarchy.

• The layout tree of the Define Device Correspondence form updates to display only the instances that are within context of the transparent instance that you have descended into.
• The schematic tree of the Define Device Correspondence form updates to display only the unbound instances and the bound instances that are within context of the transparent instance that you have descended into.
  Cadence does not advise introducing an additional hierarchy in Layout XL and recommends that you keep the schematic and the layout hierarchies in sync as much as possible. But, for design situations where an additional level of hierarchy is required, Layout XL can help by keeping the additional, introduced hierarchy XL-compliant.

When working with a transparent layout hierarchy, using the following commands in Layout XL or a higher tier can ensure XL-compliance:

• Make Cell
• Set Instance as Transparent
• Unset a Transparent Instance
• Flattening a Layout Instance

Related Topics

Staying XL-Compliant by Manipulating the Layout Hierarchy - Part 1 (Introduction)

Staying XL-Compliant by Manipulating the Layout Hierarchy - Part 2 (Using the Flatten Command)

Staying XL-Compliant by Manipulating the Layout Hierarchy - Part 3 (Using the Make Cell Command)

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