Comments on "Signature analysis for multiple output circuits" by R. David

The probability of a fault-free signature has been calculated in the above-named paper (see ibid., vol.C-35, no.9, p.830-7 (1986)) and in an earlier paper by the same author (see ibid., vol.C-29, no.7, p.668-73 (1980)). Implicitly, it was considered as the probability of masking due to signature analysis. It is shown here that this does not correspond exactly to the probability of aliasing. A new definition is given. The difference centers on the event where there are no bit errors in the data to be compressed. When the response of the circuit is correct, the signature is fault-free. However, there is no aliasing.<>