Exploiting Hardware Unobservability for Low-Power Design and Safety Analysis in Formal Verification-Driven Design Flows

Formal techniques for the functional verification of System-on-Chip (SoC) hardware have matured significantly over the last years. They can penetrate deeply into a design to exhibit complex functional dependencies between various design components in terms of detailed logical and temporal relationships. They can also provide a well-defined formal relationship between an abstract system model of a design and its concrete implementation at the register-transfer level (RTL). This paper shows how such knowledge available from formal verification can be “condensed” into a database that stores all registers and flip-flops, at which time points they are actually relevant for the correct behavior of the design and when they are not. We show that the comprehensive information on temporary unobservabilities in the design can be of great value to reach two nonfunctional design goals that play a dominant role in many design flows: safety and low power consumption. This paper presents techniques to assess the effects of soft errors by single-event upsets (SEUs) with formal precision and to relate the results of the proposed analysis to an abstract system model. For example, our analysis can determine which soft errors may lead to a system “crash” and which are guaranteed not to cause any harm. For the application of the proposed approach in power optimization, this paper presents techniques for clock gating and power gating. For the examined designs, we observe a reduction of power consumption between 10% and 50% on top of the state-of-the-art commercial power synthesis.