ECE2030 Introduction to Computer Engineering Lecture 6: Canonical (Standard) Forms Prof. Hsien-Hsin Sean Lee School of Electrical and Computer Engineering Georgia Tech
Boolean Variables A multi-dimensional space spanned by a set of n Boolean variables is denoted by Bn A literal is an instance (e.g. A) of a variable or its complement (Ā)
SOP Form A product of literals is called a product term or a cube (e.g. Ā·B·C in B3, or B·C in B3) Sum-Of-Product (SOP) Form: OR of product terms, e.g. ĀB+AC A minterm is a product term in which every literal (or variable) appears in Bn ĀBC is a minterm in B3 but not in B4. ABCD is a minterm in B4. A canonical (or standard) SOP function: a sum of minterms corresponding to the input combination of the truth table for which the function produces a “1” output.
Minterms in B3
Canonical (Standard) SOP Function
POS form (dual of SOP form) A sum of literals is called a sum term (e.g. Ā+B+C in B3, or (B+C) in B3) Product-Of-Sum (POS) Form: AND of sum terms, e.g. (Ā+B)(A+C) A maxterm is a sum term in which every literal (or variable) appears in Bn (Ā+B+C) is a maxterm in B3 but not in B4. A+B+C+D is a maxterm in B4. A canonical (or standard) POS function: a product of maxterms corresponding to the input combination of the truth table for which the function produces a “0” output.
Maxterms in B3
Canonical (Standard) POS Function
Convert a Boolean to Canonical SOP Expand the Boolean eqn into a SOP Take each product term w/ a missing literal A, “AND” () it with (A+Ā)
Convert a Boolean to Canonical SOP F ABC 1 1 Minterms listed as 1’s 3 7
Convert a Boolean to Canonical SOP
Convert a Boolean to Canonical POS Expand Boolean eqn into a POS Use distributive property Take each sum term w/ a missing variable A and OR it with A·Ā
Convert a Boolean to Canonical POS
Convert a Boolean to Canonical POS F ABC 1 Maxterms listed as 0’s 2 4 5 6
Convert a Boolean to Canonical SOP F ABC 1 1 Minterms listed as 1’s 3 7
Convert a Boolean to Canonical POS
Convert a Boolean to Canonical SOP
Interchange Canonical SOP and POS For the same Boolean eqn Canonical SOP form is complementary to its canonical POS form Use missing terms to interchange and Examples F(A,B,C) = m(0,1,4,6,7) Can be re-expressed by F(A,B,C) = M(2,3,5) Where 2, 3, 5 are the missing minterms in the canonical SOP form