Soft Block Generation in Design Planning and Analysis

When the schematic components in a design have missing layout representations, the Design Planning and Analysis (DPA) tool generates a virtual hierarchy at the top level that represents the hierarchy in the layout. When the schematic counterparts themselves are missing, the DPA tool can create soft blocks for such schematic representations during virtual hierarchy generation.

For top-level virtual hierarchy blocks that have missing schematic or a schematic with only pins but no instances or physical binding, the DPA tool first searches for soft block definitions through the Configure Physical Hierarchy (CPH) window. If relevant definitions are found, matching soft blocks are generated in the layout canvas.

If relevant definitions are not found in CPH, DPA generates soft blocks and PR boundary based on the corresponding symbol view using the following environment variables:

• initIOPinLPP, initIOPinWidth, and initIOPinHeight for soft blocks
• initAreaUitlization, aspectRatio, and lxGenerateArea for PR boundary
  
  Any top-level virtual hierarchy blocks that have an ignore for generation attribute set on the instances do not have their soft blocks created in the virtual hierarchy.

The generated virtual hierarchies and soft blocks can be accessed using the Navigator assistant under the Virtual Hierarchy data set. See Virtual Hierarchy Data Sets in Navigator Assistant.

The placement of pins in soft blocks is performed based on the symbol view, which results in creation of identical pins in terms of height, width, and layer purpose-pair. Placement based on the physical configuration defined in CPH lets you specify a unique value for pins and the PR boundary.

To control the area of a soft block at generation, you can set an area property on the schematic symbol. If the soft block is generated using this area property, the specified area is then reported as the initial soft block area and is used to measure any area changes during a Stretch or Chop operation.

Related Topics

Generating a Soft Block for a Virtual Hierarchy