Thus, one of the crucial issues to be considered is
how to give support to the frequency and amplitude
measurements. Moreover, it would be preferable to
encode them into a single digital signal. Unfortunately,
although frequency information is easily encoded to
digital, this is not the case for amplitude. To solve this
problem, Roh and Abraham recently proposed the use
of a Time-division Multiplexing comparator [7]. A
solution based on oversampling data converters has
been proposed by the present and other authors in [4,8].
In this way, the generated waves are encoded to digital
and thus, can be processed either internally or
externally by a purely-digital tester. The work in [8]
discusses the problem of accessing internal nodes and
gives ideas about possible procedures for on-chip
decision mechanisms.