Lookup Structure
Structured databases map simulated failure patterns to specific physical defects across bare circuit boards or assembled substrate networks. During automated in-circuit and boundary scan testing, a fault dictionary translates unexpected electrical measurements into precise physical fault callouts. Test systems match observed nodal logic states or impedance deviations directly against stored fault patterns.
This cross-reference table reduces diagnostic time by identifying candidate short circuits or open pins without manual probing. The database structure applies specifically to static structural defects defined during design-for-test development.
Generation Logic
Electronic design automation tools simulate specific circuit faults by systematically introducing open traces and pin short circuits into the schematic model. Logic simulators compute the resulting test vector output for each fault condition, populating the fault dictionary with unique signature vectors. Matrix reduction algorithms condense redundant signatures to optimize diagnostic lookup speed during high-volume manufacturing.
When two distinct structural defects yield identical output vectors, the software groups the fault candidates into a single diagnostic class. Modern automated test systems upload these condensed matrices into local tester memory prior to production batch execution.
Diagnostic Boundary
Lookup mapping fails when unmodeled multiple simultaneous faults create compound output signatures not present in the precomputed database. Analog component tolerances that drift beyond nominal limits without complete catastrophic failure produce signatures that bypass binary logic tables. Structural changes made to circuit layout without regenerating the reference matrix cause false diagnostic output.
