Question and Answers:

1. What is the main advantage of compiled code simulator versus event driven simulator?

Answer: In case of compiled code simulator the whole circuit (i.e., all gates) needs to be simulated when input pattern changes. In case of event driven simulation, only those gates are required to be simulated whose inputs change because of change in the input. So, event driven simulation is more time efficient compared to compiled code simulation.

......2. Which fault simulation algorithm is most dependent on architecture of the computer simulating it?
Answer: Concurrent fault simulator is mostly dependent on the architecture of the computer simulating it because speed (i.e., number of faults simulated per iteration) depends on the bit width of the word of the computer. If the bit width is w, then w-1 faults can be simulated in an iteration.

.......3. When the procedure for test pattern generation by fault simulation is stopped and ATPG by sensitization–propagation –justification approach is taken?

Answer: Under two cases, test pattern generation by fault simulation is stopped.

(i)  A high percentage of faults are detected by fault simulation; it implies that most of the easy to test faults are covered and the ones remaining are difficult to test faults.

(ii)  For a significant number of random patterns at a stretch, new faults covered are nominal; it implies that in the circuit a substantial percentage of faults are difficult to test and one should resort to sensitization–propagation –justification approach.