Lecture 4' Boolean Algebra Chap' 3

1
Lecture 4. Boolean Algebra Chap. 3
EE203 Digital System Design

• Mar. 14,2006

2
Objectives

• Topics introduced in this chapter
• Apply Boolean laws and theorems to manipulation
  of expression
• - Simplifying
• - Finding the complement
• - Multiplying out and factoring
• Exclusive-OR and Equivalence operation(Exclusive-
  NOR)
• Consensus theorem

3
3.1 Multiplying Out and Factoring Expressions
To obtain a sum-of-product form ? Multiplying
out using distributive laws
Theorem for multiplying out






Y.
Y
or

Y
1
0
Z)
Y(1

to
reduces

3)
-
(3

0,
X

If






Z.

or Z

Y
0
Z
Y)Z
(1

to
reduces

3)
-
(3

1,


X

If


valid.
always

is
it

1,
X

and

0


X
both
for

valid
is
equation

the
because

factoring
for

3)
-
(3

Theorem

of

use

the
s
illustrate

example

following

The
8
7
6




)
'
)(
(
'
B
A
C
A
C
A
B
A
Theorem for factoring
4
3
4
2
1
4
3.1 Multiplying Out and Factoring Expressions
Theorem for multiplying out
Multiplying out using distributive laws
Redundant terms
multiplying out (1) distributive laws (2)
theorem(3-3)
What theorem was applied to eliminate ABC ?
5
3.1 Multiplying Out and Factoring Expressions
To obtain a product-of-sum form ? Factoring
using distributive laws
8
7
6




Theorem for factoring
)
'
)(
(
'
B
A
C
A
C
A
B
A
4
3
4
2
1
Example of factoring
6
3.2 Exclusive-OR and Equivalence Operations
Exclusive-OR
Truth Table
Symbol
7
3.2 Exclusive-OR and Equivalence Operations
Theorems for Exclusive-OR
8
3.2 Exclusive-OR and Equivalence Operations
Equivalence operation (Exclusive-NOR)
Truth Table
Symbol
9
3.2 Exclusive-OR and Equivalence Operations
Exclusive-NOR
Example of EXOR and Equivalence
Useful theorem
10
3.3 The Consensus Theorem
Consensus Theorem
Proof
consensus
Example
consensus
Dual form of consensus theorem
Example
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3.3 The Consensus Theorem
Example eliminate BCD
Example eliminate ABD, ABC
Example Reducing an expression by adding a term
and eliminate.
Consensus Term added
Final expression
12
3.4 Algebraic Simplification of Switching
Expressions
1. Combining terms
Example
Adding terms using
Example
2. Eliminating terms
Example
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3.4 Algebraic Simplification of Switching
Expressions
3. Eliminating literals
Example
4. Adding redundant terms (Adding xx,
multiplying (xx), adding yz to xyxz, adding
xy to x, etc)
Example
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3.5 Proving Validity of an Equation

• Proving an equation valid
• 1. Construct a truth table and evaluate both
  sides tedious, not elegant method
• Manipulate one side by applying theorems until it
  is the same as the other side
• Reduce both sides of the equation independently
• Apply same operation in both sides ( complement
  both sides, add 1 or 0 )

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3.5 Proving Validity of an Equation
Prove
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3.5 Proving Validity of an Equation
Some of Boolean Algebra are not true for
ordinary algebra
Example
True in ordinary algebra
Not True in Boolean algebra
True in ordinary algebra
Example
Not True in Boolean algebra
Example
True in ordinary algebra
True in Boolean algebra
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Lecture 5 Applications of Boolean Algebra and
Minterm and Maxterm Expansion Chap. 4
EE203 Digital System Design

• Mar. 16, 2006
• Professor Kyu Ho Park
• http//core.kaist.ac,kr
• kpark_at_ee.kaist.ac.kr

18
Objective

• Conversion of English Sentences to Boolean
  Equations
• Combinational Logic Design Using a Truth Table
• Minterm and Maxterm Expansions
• General Minterm and Maxterm Expansions
• Incompletely Specified Functions (Dont care
  term)
• Examples of Truth Table
  Construction
• Design of Binary Adders(Full
  adder) and Subtracters

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4.1 Conversion of English Sentences to Boolean
Equations
- Steps in designing a single-output
combinational switching circuit

• Find switching function which specifies the
  desired behavior of the circuit
• Find a simplified algebraic expression for the
  function
• Realize the simplified function using available
  logic elements

1. F is true if A and B are both true ? FAB
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4.1 Conversion of English Sentences to Boolean
Equations
1. The alarm will ring(Z) iff the alarm switch is
turned on(A) and the door is not closed(B), or
it is after 6PM(C) and window is not closed(D)
2. Boolean Equation
3. Circuit realization
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4.2 Combinational Logic Design Using a Truth Table
- Combinational Circuit with Truth Table
When expression for f1 ?
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4.2 Combinational Logic Design Using a Truth Table
Original equation ?
Simplified equation ?
Circuit realization ?
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4.2 Combinational Logic Design Using a Truth Table
- Combinational Circuit with Truth Table
When expression for f0 ?
When expression for f 1 ? and take the
complement of f
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4.3 Minterm and Maxterm Expansions
- literal is a variable or its complement (e.g.
A, A)
- Minterm, Maxterm for three variables