Monday, January 19, 2015

Logic Circuits: 3-bit K-Map (Karnaugh Map) problem #2

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Simplify the following function using K-map: F(A,B,C) = Σ(0,2,3,7)

Solution:
K-map of F(A,B,C) = Σ(0,2,3,7)
This is a summation of minterms, therefore, 0, 2, 3, and 7 are all 1's. We can't group the 4 of them together since they don't form a square in the K-map (see figure). We can group them by pair. Notice the ones grouped in red. They can be grouped together since the difference between bits 00 and 10 is only 1 bit, and we can only group together bits that are 1 bit apart (review Gray Code, K-map is in Gray Code). When dealing with minterms, an x is equal to 1 and an x' is equal to 0. Zero's will be listed as x' and one's as x.

We need to list the variables. For the first term (red group), A has two 0's, B has one 0 and one 1, and C has two 0's. For the second term (green group), A has one 0 and one 1, B has two 1's, and C has two 1's as well.

F = (A' + A') (B' + B) (C' + C') + (A' + A) (B + B) (C + C)

Boolean Algebra Theorems state that x'+x'=x', x+x=xx'+x=1


= (A' ∙ 1 ∙ C') + 1 ∙ B ∙ C

They, also, state that x∙x=x, x∙1=x, and x'∙1=x'. Thus, we get the answer.


F = (A' ∙ C) + (B ∙ C)

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