TAILIEUCHUNG - Standardized Functional Verification- P18

Standardized Functional Verification- P18:Every manager who brings a design to tape-out or who purchases IP must eventually face these questions. The ability to answer these questions based on quantitative analysis is both vital and yet elusive. In spite of the enormous technical advances made in IC development and verification software, the answers to these questions are still based largely on guesswork and hand waving. | Standard Views of Functional Coverage 155 Fig. . Example of time-based view Because tools are not yet capable of producing exhaustive coverage in a practical timeframe it remains necessary and prudent to develop good judgment regarding this sort of dynamic behavior. A time-based view of bus utilization that is largely uniform or that is not able to reach and sustain extremes of usage indicates that coverage is poor and unexposed bugs are likely to remain in the RTL. A time-based view that shows lots of burst behavior with sustained high levels and low levels of activity with both rapid and slow transitions between extremes indicates that coverage is much much better and that the risk of unexposed bugs is much lower. Standard Views of Functional Coverage The views described in this chapter are actually quite simple and obvious. It is not the type of views that must be standardized but rather that which is viewed that merits standardization. In other words the standard variables and their values must be made available for arbitrary viewing by interested 156 Chapter 6 - Analyzing Results parties whether they are from upper management or from a prospective customer of IP. These different views are all quite common and readily available with commercial verification tools. When the standard results are available to such viewers then it is easy and economical to produce the views on demand. Data-mining of the standard results and refining the ore with these views can provide useful insights into the level of coverage achieved for the different subspaces of the design. Summary A verification methodology that takes full advantage of standard results will increase productivity in the long run. Everything about the verification of the target can be determined from these standard results. Until 100 functional coverage can be achieved in commercially interesting timeframes it remains necessary to sample the results. If every view examined indicates thorough .