RATS: Restoration-Aware Trace Signal Selection for Post-Silicon Validation

Post-silicon validation is one of the most important and expensive tasks in modern integrated circuit design methodology. The primary problem governing post-silicon validation is the limited observability due to storage of a small number of signals in a trace buffer. The signals to be traced should be carefully selected in order to maximize restoration of the remaining signals. Existing approaches have two major drawbacks. They depend on partial restorability computations that are not effective in restoring maximum signal states. They also require long signal selection time due to inefficient computation as well as operating on gate-level netlist. We have proposed a signal selection approach based on total restorability at gate-level, which is computationally more efficient (10 times faster) and can restore up to three times more signals compared to existing methods. We have also developed a register transfer level signal selection approach, which reduces both memory requirements and signal selection time by several orders-of-magnitude.