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A city council has four members, \(A, B, C,\) and \(D .\) Each member votes on a proposition (1 for yes, 0 for no). Find a minimized SOP logic expression having inputs \(A, B, C,\) and \(D\) and output \(X\) that is high when the vote is tied and low otherwise.

Short Answer

Expert verified
Tie happens when the expression \( X = A'B'C + AB'C' + ABC' \) is satisfied.

Step by step solution

01

Understanding the Problem

The proposition results in a 'tie' if the number of 'yes' votes (1s) equals the number of 'no' votes (0s). In a 4-member group, a tie happens when exactly two members vote 'yes' and the other two vote 'no' (i.e., 2 ones and 2 zeros).
02

Listing All Possible Outcomes

Enumerate all possible combinations of votes. For four members, the total combinations are from 0000 to 1111 in binary, which range from 0 to 15 in decimal. Only include combinations where there are two 'yes' votes (1s) and two 'no' votes (0s).
03

Identifying Tie Combinations

The combinations where votes are tied (2 'yes' and 2 'no') are: 0011, 0101, 0110, 1001, 1010, and 1100. These correspond to rows 3, 5, 6, 9, 10, and 12 in a truth table.
04

Expressing Tie Using Minterms

Write out the minterms for the identified tie combinations: 0011 = A'B'C'D, 0101 = A'BC'D', 0110 = A'BC'D, 1001 = AB'C'D', 1010 = AB'C'D, 1100 = ABC'D'.
05

Minimizing the SOP Expression

Use Karnaugh map or Boolean algebra to simplify these minterms: \[ A'B'C'D + A'BC'D' + A'BC'D + AB'C'D' + AB'C'D + ABC'D' \]. Simplified expression is \[ X = A'B'C + AB'C' + ABC' \].
06

Verifying the Simplified Solution

Check each combination against the simplified expression \( X = A'B'C + AB'C' + ABC' \) to ensure it holds true for the specified tie combinations and false otherwise.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

SOP (Sum of Products)
The Sum of Products (SOP) is a method used in digital logic design to express a Boolean function as a logical expression. The SOP form is a series of AND operations (products) that are combined using OR operations (sum). It is highly structured and commonly used because it simplifies an entire truth table into a single expression, making analysis and implementation easier for multi-variable logic problems.

In our exercise, the aim is to derive a minimized SOP expression for a situation where city council members' votes result in a tie. A tie is when the number of 'yes' votes equals the number of 'no' votes. The process includes identifying specific minterms where this condition is met and expressing them in product terms. These terms are then summed to get the SOP form. In our case, the SOP expression consisted of minterms from combinations like 0011 or 1100.

The beauty of SOP lies in its clarity and optimization potential. Boolean logic allows these expressions to be reduced further, thus simplifying the logic diagram for practical use.
Karnaugh Map
The Karnaugh Map (K-map) is a visual representation technique used to simplify Boolean expressions without extensive calculations. It is a grid-like method that helps to reduce the complexity of SOP expressions and is especially handy with variables up to six. By organizing truth table values into a matrix, adjacent cells denote minterms differing by only one variable, allowing for simplification via grouping.

Creating a K-map involves plotting the truth table results for our proposition vote tie problem. For the cases where there are two 'yes' and two 'no' votes, the K-map helps us visually identify where minterms can be grouped to eliminate unnecessary variables, creating a simpler expression. In our example, this led to the reduction of the initial SOP to a more manageable size of logical terms such as \(A'B'C + AB'C' + ABC'\).

The advantage of a K-map is its ability to visually streamline the simplification process by minimizing logical redundancies, thus enhancing the efficiency in implementing digital circuits.
Boolean Algebra
Boolean Algebra is the mathematical framework used for analyzing and simplifying logical expressions and is foundational in digital circuit design. It uses binary variables, usually in the form of 0s and 1s, and logical operations such as AND, OR, and NOT to model digital systems.

In this exercise, Boolean Algebra is employed to minimize the SOP representation of the vote tie problem. By applying different laws, such as De Morgan's Theorems, Distribution, or Consensus, we can simplify the logical expression. Through Boolean manipulations, the original lengthy expression: \(A'B'C'D + A'BC'D' + A'BC'D + AB'C'D' + AB'C'D + ABC'D'\) was shortened to the much more efficient form of \(X = A'B'C + AB'C' + ABC'\).

Understanding these algebraic laws not only aids in reducing complex expressions but also ensures that digital logic systems are designed in the most efficient way possible.
Truth Table
A Truth Table is an essential tool for analyzing and understanding the behavior of Boolean expressions and logical operations. It systematically displays all possible outcomes of a logic function as it relates input combinations to their corresponding outputs.

In solving the tie vote problem, a truth table helps illustrate all potential configurations of votes from the council members. This table makes it easy to identify which combinations result in a tie (namely 2 'yes' and 2 'no' votes). For four variables like \(A, B, C, \) and \(D\), there are 16 possible combinations (from 0000 to 1111). But only specific combos meet the tie criteria: 0011, 0101, 0110, 1001, 1010, and 1100.

By documenting these in a truth table, it's straightforward to pick out the data for further simplification into an SOP form using techniques like K-maps or Boolean Algebra, ensuring clarity and precision in logical design.

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Most popular questions from this chapter

Replace the AND operations by ORs and vice versa by applying De Morgan's laws to each of these expressions: a. \(F=A B+(\bar{C}+A) \bar{D}\) b. \(F=A(\bar{B}+C)+D\) c. \(F=A \bar{B} C+A(B+C)\) d. \(\begin{aligned} ^{*}F=&(A+B+C)(A+\bar{B}+C) \\ &(\bar{A}+B+\bar{C}) \end{aligned}\) e. \(^{*}F=A B C+A B C+\overline{A B C}\)

Describe a method for proving the validity of a Boolean algebra identity.

We need a logic circuit that gives an output \(X\) that is high when an error in the form of an unused code occurs in a given \(\mathrm{BCD}\) codeword. The inputs to the logic circuit are the bits \(B_{8}, B_{4}, B_{2},\) and \(B_{1}\) of the \(B C D\) codeword. (The most significant bit is \(B_{8}\), and the least significant bit is \(B_{1}\).) Construct the Karnaugh map and write the minimized SOP and POS expressions for \(X\)

How many bits per word are needed to rep resent the decimal integers 0 through \(100 ? 0\) through \(1000 ? 0\) through \(10^{6} ?\)

Design a logic circuit to control electrical power to the engine ignition of a speed boat. Logic output \(I\) is to become high if ignition power is to be applied and is to remain low otherwise, Gasoline fumes in the engine compartment present a serious hazard of explosion. A sensor provides a logic input \(F\) that is high if fumes are present. Ignition power should not be applied if fumes are present. To help prevent accidents, ignition power should not be applied while the out drive is in gear. Logic signal \(G\) is high if the out drive is in gear and is low otherwise. A blower is provided to clear fumes from the engine compartment and is to be operated for five minutes before applying ignition power. Logic signal \(B\) becomes high after the blower has been in operation for five minutes. Finally. an emergency override signal \(E\) is provided so that the operator can choose to apply ignition power even if the blower has not operated for five minutes and if the out drive is in gear. but not if gasoline fumes are present. a. Prepare a truth table listing all combinations of the input signals \(B, E, F,\) and \(G .\) Also, show the desired value of \(I\) for each row in the table. b. Using the SOP approach, write a Boolean expression for \(I\). c. Using the POS approach, write a Boolean expression for \(I\) d. Try to manipulate the expressions of parts (b) and (c) to obtain a logic circuit having the least number of gates and inverters Use AND gates, OR gates, and inverters.

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