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Unformatted text preview: 1 ECE 15A Fundamentals of Logic Design Lecture 4 Malgorzata MarekSadowska Electrical and Computer Engineering Department UCSB 2 Last time : We have proved all fundamental laws stated for sets. Theorem 1 : Every statement or algebraic identity deducible from P1 P4 remains valid if the operations (+) and ( ), and the identity elements 0 and 1 are interchanged throughout. Theorem 2: For every element a in Boolean algebra B: a+a =a and aa = a. Theorem 3 : For each element a in Boolean algebra B, a + 1 = 1 and a 0 = 0. Theorem 4 . For each pair of elements a, b in a Boolean algebra B, a + ab = a and a(a + b) = a. Theorem 5 . In every Boolean algebra B each of the binary operations (+) and ()is associative. That is, for every a, b and c in B: a + (b + c) = (a + b) + c and a(bc) = (ab)c 2 3 Last time: cont. Theorem 6. The element a associated with element a in a Boolean algebra is unique. Theorem 7. For every a in a Boolean algebra B, (a)=a. Theorem 8 . In any Boolean algebra, 0 = 1 and 1 = 0. Theorem 9. For every a and b in Boolean algebra B, (ab) = a + b and (a+b) = ab [De Morgans laws] 4 Example: 2valued Boolean algebra Boolean algebra on B={0,1} and operators {+, ,} From theorem 2 [a+a=a, aa=a]: 0+0 = 0 1+1 = 1 0 0 = 0 1 1 = 1 From Theorem 3 [a+1=1, a0=0]: 0+1=1 0 0 = 0 1+1 = 1 1 0 = 0 From Theorem 8: 0 = 1 1 = 0 + 0 1 0 0 1 1 1 1 0 0 0 1 1 0 1 3 5 Today: Boolean functions B={0,1} B is a set of all tuples (b1, b2, bk), such that bi is either 0 or 1 for all 1<=i<=k. B may be viewed as the set of all kbit strings. Example: k = 3. B = {(0,0,0), (0,0,1), (0,1,0), (0,1,1),(1,0,0),(1,0,1),(1,1,0),(1,1,1)}. B has a size of 2 . k k 3 k k 6 Boolean function Boolean function f: B > B , k>0, m>0. kbit input is mapped to an mbit output k m B B k m mapping Domain Codomain An element in a domain is assigned one element in the codomain. m=1: singleoutput function. 4 7 Boolean functions algebraic form Constant a symbol which represents a specified element of Boolean algebra Variable: a symbol a,b,c,etc. representing unspecified elements Literal  a variable with specified polarity: a,a,b, b,etc. Boolean function : any expression which represents the combination of finite set of symbols, each representing a constant or variable, by the operations of (+), ( ), or (). Examples of singleoutput functions: F1(a,b,c,d,x)=(a+b)c + (a+bx)d F2(a,b,c,d)= abc+ad 8 Disjunctive normal form Definition. A Boolean function is in disjunctive normal form in n variables x1,x2,,xn, for n>0, if The function is a sum of terms where No two terms are identical 0 and 1 are in disjunctive normal form in n variables for any n>0....
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This note was uploaded on 05/29/2009 for the course ECE 15A taught by Professor M during the Winter '08 term at UCSB.
 Winter '08
 M

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