As electronic systems become more complex, troubleshooting manufacturing and field failures becomes more difficult. Hard failures (i.e. permanent changes in a device that lead to reproducible failures) are straightforward to isolate and determine a root cause. The more problematic area is “no trouble found” or NTF – meaning the original failure is difficult (if not impossible) to reproduce. There are several sources of NTF: Noise – Signal reflections, cross-talk, ground bounce Timing marginality – Variations in rise times and delay times over temperature and voltage Weak cells (memory) – leakage in DRAM, read-write instability in SRAM Soft errors - upsets in memory and logic due to radiation from alpha particles within the IC package or neutrons generated from cosmic rays Each of …