Dynamic selection of trace signals for post-silicon debug

Abstract

Post-silicon validation is one of the most expensive and complex tasks in today's System-on-Chip (SoC) design methodology. A major challenge in post-silicon debug is limited observability of the internal signals. Existing approaches address this issue by selecting a small set of useful signals. These signal states are stored in an on-chip trace buffer during execution. The applicability of existing methods is limited to a specific debug scenario where every component has equal importance all the time. In reality, a verification engineer would like to focus on a specific set of components (functional regions). Some regions can be ignored in a certain duration during execution due to clock gating and other considerations. Similarly, certain regions may be well verified datapath and less likely to have errors compared to other control-intensive regions. In this paper, we propose an efficient signal selection algorithm and a low-overhead trace controller design that would enable verification engineers to dynamically select a set of trace signals for improved error detection. Our experimental results using both ISCAS'89 benchmarks and Opencores circuits demonstrate that our approach can detect up to 3 times more errors compared to existing techniques.