Virtuosity: Read Mode Done Right

Because of the ease with which you can set up complex sweep, corner and Monte Carlo simulations, the Virtuoso ADE tools are frequently used to perform verification and regression simulation runs.  Those runs are most commonly done by accessing cellviews in read-only mode (RO), so that the “golden” simulation setups are not modified and there is no need to check out the cellviews from the design management (DM) vault.

Opening an adexl view in read-only mode allows you to run simulations, but when you exit, the simulation results are deleted.  In addition, if any small modifications are made in RO mode—correcting a typo, or adjusting a path—those changes are lost unless you save them to a new cellview, which is inconvenient and can lead to confusion.

In Virtuoso® ADE Assembler and Virtuoso® ADE Explorer, working with maestro views in read-only mode is more powerful and flexible.  The added functionality of RO mode also enables Virtuoso® ADE Verifier to run the maestro views it needs for verification so that the end users’ work is not disrupted.

Background

Before we get into the capabilities of RO mode itself, let me give a quick overview of where ADE Explorer and ADE Assembler store their data.  There are 3 kinds of data we’re dealing with:

1. Setup
   • The setup database contains corners, variables and run options for the active setup and for all history checkpoints
   • The test states contain setup specific to each test (analyses, outputs and simulation options)
2. Waveforms and netlists
   • For example, the Interactive.X directory with individual leaf directories for each corner
3. Results database
   • Contains results values for output expressions across tests, sweeps and corners.

Now, where are these 3 kinds of data stored?

1. Setup information is stored in the maestro Lib/Cell/View, so it can be managed under the DM system. 
2. Waveform and netlist data is stored in the “project directory”
   1. You can find this location in your environment by typing: envGetVal(“asimenv.startup” “projectDir”) in the CIW
   2. If envGetVal(“adexl.results” “saveResDir”) is set, that will override the projectDir

3. Results database is by default stored in the maestro Lib/Cell/View
   1. If envGetVal(“adexl.results” “saveDir”) is set, that will override the default behavior.
   2. Many users store the results database with the waveforms and netlists, which means that data is not design managed. 

Why am I telling you all of this? 

Because, when you run in read-only mode, by definition, you don’t want to save (or modify) anything in the maestro Lib/Cell/View.  That means the setup information and the results database need to be stored in some other location.

RO mode for ADE Assembler

When you open a maestro view in ADE Assembler for read, all its information will be stored in the same directory as the waveform and netlist data (#2 above).  A copy of the setup database and the test states files will be stored here.  When you click the run button, RO mode will create histories with a “.RO” suffix.  For example, Interactive.2.RO.  The results database for each RO history will also be stored here.  Unlike ADE XL, when you exit, the data in that directory will remain.

A maestro view can be opened multiple times in RO mode.  The RO history number will increment with each run in all open sessions.

Why is this good?

When you open the maestro view in edit mode, ADE Assembler will use the history information created during the RO session to enable you to move an RO history into a “View History” so that it becomes just like any other history that was created in edit mode.  You can do this using the RMB menu over the RO history in the History tab of the Data View.

After that, the results database from that history can be managed under DM and you can use RMB->Load Setup to Active on that history to retrieve any setup changes you made in RO mode.

What about Virtuoso ADE Explorer?

When you use ADE Explorer in edit mode, each simulation run overwrites the ExplorerRun.0 history.  In RO mode, it will create and overwrite a history named ExplorerRORun.0.RO. 

Multiple RO Explorer sessions can be opened, but all RO sessions will write/overwrite the same history.

Related Resources

• Virtuoso ADE  Explorer User Guide
• Virtuoso ADE Assembler User Guide

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Virtuosity has been our most viewed and admired blog series for a long time that has brought to fore some lesser known, yet very useful software and documentation improvements, and also shed light on some exciting new offerings in Virtuoso. We are now expanding the scope of this series by broadcasting the voice of different bloggers and experts, who would continue to preserve the legacy of Virtuosity, and try to give new dimensions to it by covering topics across the length and breadth of Virtuoso, and a lot more… Click Subscribe to visit the Subscription box at the top of the page in which you can submit your email address to receive notifications about our latest Virtuosity posts. Happy Reading!

Stacy Whiteman