DFT · Topic
ATPG — Pattern Generation, Fault Simulation & Coverage
Automatic test pattern generation — how patterns are derived from a fault model, what fault simulation measures, and why coverage plateaus.
ATPG works backwards from a fault: to detect it, the tool must find a pattern that both activates the fault site and propagates its effect to somewhere observable. That is why coverage is never simply a function of effort — a fault in logic that nothing can control, or whose effect nothing can observe, is untestable no matter how long the tool runs. Reading a coverage report is largely about telling those apart from faults the tool merely has not reached yet.