Custom IC Design Blogs

Hi, I'm Colin Thomson, Product Engineering Architect at Cadence Design Systems, Inc. My responsibilities include engaging with customers to offer them pathbreaking solutions for their Custom IC layout design challenges and to help them get the desired outcomes. Most recently, I have been helping customers create efficient advanced node layout designs using our novel Design Planning and Analysis (DPA) tool, which coherently brings together all the 3 sides of a physical design process—Design, Plan, and Analysis. Through this series of blogs, I hope to share information that should help you adopt the Design Planning and Analysis tool for your designs. Stay tuned...

In Episode 1 of the blog series, I explained how DPA can simplify things for a layout designer. This time around, I want to shed some light on the design components supported by DPA, the advantages of using each of the components, and how you can use these objects effectively when using DPA for your design.

How Can I Plan Efficiently in DPA

Due to increasing time pressure on design cycles, the planning process often begins before the design is complete. This means designers are using incomplete or missing schematics in early planning stage, design changes are likely happening while the planning process is underway, and the need for hierarchical refinement arises much later in the flow.

DPA can help you overcome these challenges, giving you access to several objects that can help you efficiently plan the layout:

• Hard blocks – already placed and routed blocks that can be used as-is or can be reused as a starting point for a subsequent revision
• Soft blocks – Soft layouts or soft abstracts that can be used for pin planning and optimization
• Virtual hierarchy – Groups representing schematic blocks can be used to enable hierarchical editing in the context of the full design

Using these objects within the Design Planning and Analysis flow can help you reduce the iterations and time needed in creating the floorplan.

How Can Soft Blocks and Virtual Hierarchies Help

Using both soft blocks and virtual hierarchies in the planning process can help improve your productivity and make your plan more efficient.

Soft blocks are:

• Real cells with a boundary and pins that are ideal for floorplanning when no schematic is available.
• Important for pin planning and optimization.
  • Level-1 pins in soft blocks can be easily accessed through the Pin Tool.

Virtual hierarchies are:

• Flat groups that allow you to edit their contents without performing an Edit-In-Place operation. This can be very advantageous when you are editing through the hierarchy, working at the top level.
• Created and sized based on their contents to provide you with more accurate floorplan estimation.
• XL-compliant by construction. You can check and update virtual hierarchies at any time during the design cycle to match their schematic source.

Can I Convert Virtual Hierarchy to Real Hierarchy

Hopefully by now, you are convinced that both real and virtual hierarchy would be beneficial for you in the design planning process. As you create the floorplan, you might need to switch from virtual hierarchy to real hierarchy or vice versa. Given the leading nature of the question in the heading, you will not be surprised that you can convert between the two! The process is extremely easy.

To move from virtual hierarchy to real hierarchy, use the Make Cell command, which:

• Creates a real cell with contents and pin positions that can be used for implementing the design.
• Supports multiple pin creation methods, including a model that allows you to create pins that takes congestion into account,

To make the return trip from real hierarchy to virtual hierarchy, use the Make Virtual Hierarchy command, which:

• Converts a real cell to a virtual cellview to allow hierarchical editing.
• Can preserve the placement and position of pins.

The Make Virtual Hierarchy command enables an ECO or reuse flow where an existing block is reused, converted to virtual hierarchy, and re-planned in the context of the full design.

So, that's all I wanted to talk about in this blog. Hope it gives you a good overview of how the DPA tool can help you be more efficient with your design planning. I plan to share more information in my upcoming blogs, watch out for the next episode.

Related Resources

For more information on Cadence circuit design products and services, visit www.cadence.com.

Contact Us

For any questions, general feedback, or even if you want to suggest a future blog topic, write to custom_ic_blogs@cadence.com.

Happy reading, and stay safe!

- Colin Thomson

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