Virtuosity: Conserve Power— Setting up Virtuoso Power Manager

‘Conserve Power' is a series of blogs that gives a sneak peek into the world of low power verification. It uncovers the functionality and potential of Virtuoso Power Manager, which lets you specify and manage the power intent for your designs. Watch out for our posts in this miniseries every Thursday between now and end of December.

Don't mistake a good setup for a satisfying conclusion - many beginning writers end their stories when the real story is just ready to begin.
Stanley Schmidt

I am sure you would have perused the first blog of this miniseries. This time I am back with a blog that briefly explains how to set up Virtuoso Power Manager before proceeding with low power verification. To run in-design checks, extract the power intent from a design, or run Conformal Low Power checks, you must first provide inputs that are required by the tool for correct identification of design topology and define the set of rules that apply to those design structures. For example, you might define a setup that identifies all the power nets in your design, creates power domains, creates supply states, or redefines the severity of certain checks.

The Virtuoso Power Manager setup typically includes a common setup and a project-specific setup.

• Common setup, as the indicated by the name, is common to a larger set of designs. It includes information about process technology, design environment, data integrity checks, and so on. This setup information is stored in a CSF-searchable location and is applied when no design-specific information is found.
• Project-specific setup comprises the user-defined and project-specific setup and design-specific details. It might include all types of settings and takes precedence over the common setup.

You can specify these settings in the Power Manager Setup form and save them in a setup file for a project to ensure that each command is run according to the project setup. The Power Manager Setup form gives you the flexibility to dynamically switch and update more than one design for power information.

The form contains Supply Nets, Libraries, Devices, In-Design Checks, Export, and Miscellaneous tabs. If you have the power intent extraction setup options in a template file, you can load or reuse them and get started!

Supply Nets Registration

Whenever you are working on a top-level design, you need to know what the supply nets are and how connectivity is propagated into the design hierarchy. While Unified Power Format (UPF) can be one of the sources to get the supply nets, you can also define supply nets directly on the Supply Nets tab of the Power Manager Setup form. If there is some consistent naming convention used for supply nets, you can use regular expressions to identify and register all the supply nets down the hierarchy. Alternatively, you can register only top-level supply nets and let the Virtuoso Power Manager trace supply nets down the hierarchy itself, which can be useful in designs where no naming convention is used. The key focus is to support registration of all supply nets.

Library Registration

Use the registration options on the Libraries tab to register library-related information. This is the modelling information, which is used by Virtuoso Power Manager to read the standard and special cells, which is essential to extract the power-related attributes of standard and special cells. When using modeling information, you don’t need to access these cells for tracing the related supplies corresponding to the boundary ports.

Device and Cell Registration

Now, let’s look at the role of the Devices tab. You can register device-related and terminal-related information on this tab of the Power Manager Setup form. The Virtuoso Power Manager utilizes the registry information to read the device type and its topology in a design. For devices with more than two terminals, you can associate terminals to have a specific mapping to various types of terminals. The correct recognition and identification of device types is important for the supply traversal to find the related supplies of the boundary ports associated with the design logic.

While traversing through the connections of transistor instances, the Virtuoso Power Manager needs to identify the gate, source, and drain terminals of the registered transistor devices. Therefore, in addition to registering the devices, you need to register the names of the device terminals of these devices. You can register terminal names with an appropriate terminal type in the Power Manager Setup form.

In-Design Checks

Next, we move to the In-Design Checks tab. The Virtuoso Power Manager supports running a set of predefined and configurable circuit checks for mixed-signal designs that include devices and standard cells. You can define the severity of reporting of these checks on the In-Design Checks tab. In the Checks Categories section, specify the severity level of the results reported for the Level Shifter, Isolation, and Bulk checks.

There is another very effective concept of supply states, which refers to the use of multiple voltages for efficient power management in designs. A supply state can be defined as a set of power and ground nets with their respective voltage values in the Supply States section. Supply states can be switched on and off or scaled up or down to different voltage values as per design requirements. IC designers choose the states as per the performance need of a design.

Some common schemes that use the power states are power gating, dynamic voltage, and frequency scaling, with a combination of different run and standby performance modes. You can also define settings for the In-Design Checks report on this tab.

Supply Set and Power Domain Registration

A power domain is part of the design that operates at a specific voltage. While capturing the power intent, you need to specify the power domains for the top level of the design. There can be a single or multiple power domains associated with the different sections of the design addressed by a specific supply set. You can define these in the Export tab of the Power Manager Setup form. During automatic extraction, Virtuoso Power Manager identifies a power net and a ground net from the pair defined explicitly in the setup as a supply set in the Export tab. It associates the supply set with the power domain as specified in the setup. You can specify a supply set as a primary supply set for the power domains mentioned in the setup. In addition, you can also define the supply set for the power and ground that cannot be paired by traversing the design hierarchy or parsing the Liberty file. There are specific design configurations where a boundary port is connected to different blocks that have different supply sets.

Miscellaneous Settings

Last but not the least is the Miscellaneous tab. You can specify generic settings, such as the Delimiter, Switch View List, Stop View List, or enable signal type, on this tab.

To conclude, you can save the power intent extraction setup options in the setup form to a template file and reuse them for the same or a different designs.

What's Next?

Stay tuned to find out about the following topics in the upcoming blogs!

1. Running In-Design Checks
2. Importing and Exporting Power Intent
3. Verifying a Design using Conformal Low Power
   
   

Happy reading, and stay safe!

Deepti Mishra Gupta

Related Resources

Virtuoso Power Manager User Guide

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