Viola Cell Library Characterization and Variation Modeling Viola is a unique, all-inclusive package for fast and accurate characterization of digital cell libraries including I/Os. The package includes Silvaco SmartSpice with fully automated stimulus generation, a library model checker, and a databook generator.The characterization engine performs detailed cell circuit analysis that automatically determines the required set of stimuli and creates SPICE decks to perform all characterization measurements for both combinational and sequential digital logic cells.