Optimal and Near-Optimal Universal Logic Modules with Interconnected External Terminals

A universal logic module (ULM) with interconnected external terminals contains m input terminals and s auxiliary function terminals. The module implements the function U( Z
1
, Z
2
,...,Z
m
) such that every Boolean function of n variables f( x
1
, x
2
,* .* * X,
n
) can be realized by an appropriate substitution of an element of 5= { x
l
,x
1
,x
2
,x
2
,...,X
n
,x
n
,g
1
,g2,..., gs} for each zj. An improved lower bound on the minimum number of terminals of a ULM of this type is derived. It is shown that certain of the " best-known" designs are in fact optimal. Improved designs are presented for ULM's of nine and ten arguments.