EntropyXZ Overview: Fault Loss Locator during Test AnalysisBased on U.S. Patent # 8,164,345 and Provisional U.S. Patent # 63/413,393

Capabilities: - Estimates lost faults during testing, gives the reason for their loss, and shows what to change to make the faults testable • Tested on > 300 Verilog designs of up to 4.6 million gates- Designer inserts test points manually or with another tool- Patented method based on Information Theory, Machine Learning, and Statistical Analysis - Entropy “warms up” the circuit by logic simulating it with random digital noise • Computes P (1), P (0), Entropy (information content), % of time signal unknown, % time in X/Z state, and Signal Activity for all signals • Statistically unbiases probabilities- Statistics used in 2 ways: • Estimate the number of untestable faults • Recommend order for inserting test points

Automatic X/Z Blocker Recommendations- Entropy™ automatically backtraces from scan D flip-flops that catch X/Z’s in each tournament • Finds X/Z generator (at the earliest point in circuit)- Chooses X/Z generators to block in each tournament • Based on untestable fault loss estimation • Uses logic 0/1/X/Z values from logic simulator • Far faster than Sequential ATPG – one EntropyXZ pass is equivalent to hundreds of Sequential ATPG runs

Test Point Recommendations- Notouch Patterns – name matching patterns to easily notouch parts of large designs • For decompressor/compressor, BIST controller, scan chains, memory models, Central Test Controller, etc.- Backtraces from scan flops catching X/Z signals to find problem source in combinational logic • Recommends X/Z signal blocker in combinational logic • Blockers remove X’s entering scan chain from D lines • Can select blocker/test point sites by # of untestable faults they cause • Can select blocker/test point sites by testability measure- Reports X/Z generators, sorted in inverse order by number of untestable faults they cause • Designer reviews the X/Z generators and test points in report & decides which to insert