Multiplexed trace signal selection using non-trivial implication-based correlation

Abstract

Silicon debug with a trace buffer provides real-time visibility to the design under debug. It traces a small subset of internal signals during its normal operation. The effectiveness of silicon debug, then, depends critically on the selection of trace signals. This paper proposes a new multiplexer-based trace signal interconnection scheme and a new heuristic for trace signal selection based on implication-based correlation. As a result, we can effectively trace twice as many signals with the same trace buffer width. We also propose a SAT-based heuristic to prune the selected trace signal list further to take into account those multi-node implications. Finally, we propose a state restoration algorithm for the multiplexer-based trace signal interconnection scheme. Experiments for sequential benchmark circuits showed that the proposed approach selects the trace signals effectively, giving superior restoration percentage compared with other techniques.