Virtual Hierarchy Generation

Virtual layout hierarchy can be defined as the “yet-to-be-realized” layout hierarchy, which is entirely based on the schematic hierarchy. The virtual layout hierarchy is a virtual representation of not only the top-cell objects, but also the objects at the lower levels, generating a completely flat hierarchy at the top-cell level.

For the parts of the schematic hierarchy that are complete, you can use the Virtual Hierarchy option on the Generate Layout form to generate a virtual hierarchy. The position of the instances in the generated virtual hierarchy is controlled using the Position field on the Design Planning and Analysis Options form. By default, individual instances are positioned inside each generated virtual hierarchy. You can group individual instances and position them inside generated virtual hierarchies using the grouped by type or grouped by type within virtual hierarchies option. The instance grouping feature is also supported at the top cellview level.

During layout generation, virtual groupings of layout instances are created in the following order:

1. Devices with the same component type. If no component type is defined, devices of the same cell master.
2. For standard cells only, devices with the same net set pair (power domain).
3. Devices of the same size based on bounding box dimensions.
4. Devices:
   a. of the same mfactor (multiplicity)
   b. of the same vector
   c. single devices
5. Non-standard cell single devices with the same bulk terminal connection named b or B or specified through component types.
   a. Layout devices with bulk terminal
   b. Schematic devices with bulk terminal, if no terminal is found on layout devices

The generated virtual hierarchy can easily be accessed using the Virtual Hierarchy data set in the Navigator assistant. If multiple instances of a virtual hierarchy need to be generated, the DPA tool creates clones of the hierarchy. The DPA tool attempts to create the maximum number of clones, as possible, for the design situation. The generated clones can be accessed using the Virtual Hierarchy Clones data subset, which is available in the Navigator assistant for the designs that have virtual hierarchy clones generated.

If the virtual hierarchy is automatically generated, you can update the contents of the hierarchy at the top level. However, for virtual hierarchies that are manually created, level-1 editing is restricted to avoid any unexpected edits to the level-1 objects. For the contents of a created virtual group to be selected and for the virtual group to be edited, the transparentGroup environment variable must be set to t.

If a Modgen constraint is set on the top-level schematic being used for virtual hierarchy generation, the Modgen is created at the top level. If the constraint is specified at a lower level, the Modgen is created inside the virtual hierarchy.

Related Topics

transparentGroup

Generating a Virtual Hierarchy

Virtual Hierarchy Data Sets in Navigator Assistant

Design Planning and Analysis Options Form

Accessing a Virtual Hierarchy Clone