
4.4 KARNAUGH MAP FUNCTION MINIMIZATION 149
with these problems, it will be helpful to identify the following three subsets of PIs:
r
Essential Prime Implicants (EPIs): Single-way PIs that must be used to achieve
minimum cover
r
Optional Prime Implicants (OPIs): Optional-way PIs that are used for alterna-
tive minimum cover
r
Redundant Prime Implicants (RPIs): Superfluous PIs that cannot be used if mi-
nimum cover is to result.
Any grouping of 2
n
adjacencies is an implicant, including a single minterm or maxterm,
but it may not be a PI. For example, a solitary quad EPI contains eight RPIs, four monads,
and four dyads, none of which are PIs.
To illustrate a simple ...