PCell Xtreme: Enabling Persistent PCells
in OpenAccess
PCells deliver many advantages in analog and custom design flows. But PCell users have two issues they want resolved:
- Until now, PCells have only worked within tools from a single vendor
This has greatly reduced the designer's choice of tools, and greatly increased the burden of developing a multi-vendor design flow in the true spirit of OpenAccess. As a result, users have resorted to GDSII streaming and database translation for many steps in a multi-vendor flow, even with OpenAccess-based tools. - Long database load times
The geometry created by a PCell submaster resides only in memory, and is lost when the layout editor closes the database. All the PCells in a design must be re-evaluated each time the design is read from disk, so the submaster geometry can be regenerated. This reevaluation can cause long delays when opening a database which contains many PCells.
PCell users have often wished for "Persistent PCells": Some way to preserve PCell layout on disk, so that any tool could read the database in its native format.
How PCell Xtreme Creates Persistent PCells
When a user instantiates a PCell in their layout editor, PCell Xtreme™ works behind the scenes to create a cache of the PCell geometry. PCell Xtreme stores this cache to disk in OpenAccess database format. The next time this database is opened, PCell Xtreme presents the cached geometry for each PCell subMaster. This cached geometry opens 10 times faster or more, because the PCell code does not need to be reevaluated. In addition, this cached geometry can be read by OpenAccess tools from many vendors.
PCell Xtreme also provides utilities to help manage the cache. These utilities enable the user to choose where the cache is stored, how long it is maintained, and when it must be purged.
Ciranova's approach to Persistent PCells has been to cache the geometry directly from the editor which created it. This means that the PCell code is always evaluated by the same software application. PCell Xtreme does not interpret or translate the PCell code. The result: The exact same cached geometry appears in every OpenAccess application.
Parameterizing Legacy PCells in Other OpenAccess Tools
PCell Xtreme provides one more benefit: The ability to instantiate and parameterize Legacy PCells in OpenAccess layout editors from many vendors. For example, when a user attempts to parameterize a SKILL® PCell using SpringSoft Laker, PCell Xtreme sends that request to Virtuoso to be interpreted. PCell Xtreme then takes the resulting geometry, caches it as an OpenAccess database element, and presents it to Laker for display. This means that your IP is no longer locked into the tools of a single vendor.