Efficient combination of trace and scan signals for post silicon validation and debug

Post-silicon validation is as an important aspect of any integrated circuit design methodology. The primary objective is to capture the bugs that have escaped the pre-silicon validation phase. A major challenge in post-silicon debug is the limited observability of internal signals in the circuit. Recent technological advances, such as embedded logic analysis, allow to store some signal states in a trace buffer. A promising direction to improve observability is to combine a small set of signals traced every cycle with a large set of scan signals stored across several cycles. The limited size of the trace buffer constrains the number of trace and scan signals that can be stored. In this paper, we propose an efficient algorithm to select a profitable combination of trace and scan signals to maximize the overall signal restoration performance. Our experimental results using ISCAS´89 benchmarks demonstrate that our approach can improve the signal restoration by 17% compared to the existing techniques.