Minterms and Maxterms, Incompletely Specified Functions, and Design and Analysis of Combinational Logic Ckts (Lecture #5). ECE 331 â€“ Digital System Design. The slides included herein were taken from the materials accompanying
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Incompletely Specified Functions,
Design and Analysis of Combinational Logic Ckts
(Lecture #5)ECE 331 – Digital System Design
The slides included herein were taken from the materials accompanying
Fundamentals of Logic Design, 6th Edition, by Roth and Kinney,
and were used with permission from Cengage Learning.
Minterms and Maxterms
Incompletely Specified Functions
Consider the following example in which the output of circuit N1 drives the input of circuit N2:
Assume the output of N1 does not generate all possible combinations of values for A, B, and C.
In particular, assume there are no combinations of values for w, x, y, and z which cause A, B, and C to assume values of 001 or 110.
“don't care” for ABC = 001
“don't care” for ABC = 110
When we realize the function, we must specify values for the don’t-cares. It is desirable to choose values which will help simplify the function. If we assign the value 0 to both X’s, then
If we assign 1 to the first X and 0 to the second, then
If we assign 1 to both X’s, then
The second choice of values leads to the simplest solution.
Design and Analysis
Combinational Logic Circuits