Using an asymmetric error model to study aliasing in signature analysis registers

Recent predictions about the aliasing behavior of linear feedback shift registers used in signature analysis with pseudorandom testing are validated experimentally. It is shown that the independent error model accurately predicts aliasing in these signature registers when test sets are selected at random. In practice, however, a circuit´s test set is fixed, and it is shown that adopting a more general asymmetric error model, of which the independent is a special case, yields more accurate aliasing information, especially in the dynamic or non-steady-state region of the aliasing profile. The only additional information needed to apply the asymmetric model to signature analysis is the fault-free sequence. Since this sequence is needed in any case to compute the fault-free signature, the model can reflect test set ordering at no extra cost