DFT · Topic
DFT Debug — Pattern Mismatches, Chain Failures & Diagnosis
Diagnosing test failures — separating shift-path problems from capture problems, localising chain breaks, and reading a diagnosis result.
The order of the questions decides whether debug takes ten minutes or two days. Logic diagnosis assumes the values unloaded from the chains are the values the capture edge latched — if the shift path itself is broken, every unloaded bit is meaningless and the tool will explain that meaninglessness in careful detail. So the flush test comes first, always: it exercises only the shift path, costs seconds, and tells you whether anything downstream can be believed.