Virtuosity: Saving Time, Effort, and Money with Express Pcells

Ever feel like you will never cross everything off your to-do list? It does not help that some tasks recur on a regular basis, and you obviously want to keep these tasks on your to-do list so they do not slip your mind. But I am sure repeating the same task over and over again leaves you unmotivated, frustrated, and bored. And, even worse, your attention and performance wander repeatedly. We all know that repetition or duplication leads to nothing but wastage of time, effort, and above all, money. 

Well, the good news is that the Express Pcell feature available in the Virtuoso environment removes all these worries. It saves us from the repeated task of evaluating the Pcells, by maintaining a cache of the evaluated Pcells on disk. This means that the Pcell code does not have to be evaluated each time a design is opened, thereby reducing the time in opening a design and avoiding duplication of effort.

Here's a quick look at some recent Express Pcell performance data, which lends weight to my endorsement of the feature.

Benefits of Express Pcells 

Let us now see how the Express Pcell feature could prove to be a boon for layout designers.

• The feature offers a tremendous performance boost in designs that contain a large number of Pcell instances. It is also useful where designs contain a moderate number of instances of complex Pcells that involve computationally intensive SKILL code.
  
  
• The cache merge utility collects and merges the contents of multiple Pcell caches located in different directories into a single Pcell cache. The cache merge utility is useful when members of a project team working on the same set of PDKs and reference libraries work from multiple project sites.
  
  
• The CDS_EXP_PCELL_DIR environment variable helps in maintaining a central Express Pcell cache for a team of layout designers working on a single design project, thereby avoiding duplication of cached Express Pcell data in any private individual cache directories. In addition, it avoids having to regenerate the entire Express Pcell cache, if needed for the entire chip or block.

How Express Pcells Work

The Pcell cache maintained by the Express Pcell feature can be used by applications both in the Virtuoso design environment and outside it. Pcells in the Virtuoso design environment use a SKILL Pcell evaluator, which is not available outside the Virtuoso design environment. For third-party applications and Cadence applications other than Virtuoso, this feature is available as an Express Pcell plug-in in OpenAccess. The plug-in enables these applications to access the pre-evaluated Pcell submasters, resulting in seamless read interoperability of SKILL Pcells.                                                                                                                                                                                                                                                                                                                           

Related Resource

• Virtuoso Parameterized Cell Reference

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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…

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Happy Reading!

Pallabi Roy