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Electronic Labs_15

# Electronic Labs_15 - Laboratory Exercise 2 7 SIM ULA TING...

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Unformatted text preview: Laboratory Exercise 2 7 SIM ULA TING PROBLEMS WITH LOGIC CIRCUITS Performance Objectives A. Discuss the technique for designing a com- bination-logic decision making circuit and implement the circuit to verify the results. B. Use Boolean simplification techniques to design, implement, and verify A VOTE SYSTEM that will indicate a majority “YES”, majority “NO”, and a “TIE” vote. Basic Concepts 1. Problem simulation with combination-logic circuits requires that all variables first be determined and identiﬁed. 2. A truth table is then constructed which includes all variables, all possible state combinations of these variables, and the desired output conditions for these com- binations. 3. A Boolean equation can then be written for each variable necessary to simulate the problem. 4. Boolean equation simplification techniques can then be utilized to allow implemen- tation of a simpler logic circuit configur- ation. 5. The logic circuit can then be constructed from the simplified Boolean equation. Introductory Information In this Laboratory Exercise we will discuss the technique of designing combination-logic circuits to simulate real problems. Although the problems presented in this Laboratory Exercise are compara- tively simple, the technique used to simulate them could apply as easily to more compex problems. The logic circuit solution, of course, may also be more complex. The use of combination-logic cir— cuits in problem simulation affords the user the opportunity of working with circuit inputs he can control, observing circuit outputs that are the result of known inputs, and realizing circuit solutions applicable to the real problem without the necessity of manipulating or controlling real variables. Additional Reading See bibliography at the back of this manual for additional reading material related to simulating problems with combination-logic circuits and logic simplification techniques. Review Laboratory Exer- cise 26 on Boolean algebra, identities, laws, and theorems. Equipment and Materials The Model ASl8145 Digital Logic Trainer with: - 4-input NAND Gates (7420) - 2-input AND Gates (7408) - 2-input OR Gates (7432) 2-input NAND Gates (7400) - 2-input NOR Gates (7402) - Hex Inverters (7404) - Switches - LED Displays cornmcoihup-m-un Objective A. Discuss the technique for designing a combination-logic decision making circuit and implement the circuit to verify the results. Preparatory Information. Simulation of a prob- lem with combination-logic circuitry requires a series of operations as discussed in the basic con- cepts. To illustrate the technique, we will simulate the problem of the farmer, the hen, the fox, and the corn. The problem is that the farmer wants to get to the other side of a river with the hen, fox, and corn all intact. Ordinarily this would not be a problem but the farmer notices that the only boat available is very small; it can only hold himself and any one of the items at a time. If he leaves the hen and the corn, the hen will eat the corn. If he leaves the fox and the hen, the fox will eat the hen. TheSe same restrictions apply when the farmer has to leave more than one item on the other side of the river after each crossing. The first step in our simulation is to identify each input variable, the desired number of output conditions,and assign letter designations to them. The letter designations are arbitrary. Hence, we will let the farmer be A, the hen will be B, the fox will be C, and the corn will be D. We can 2 7-1 ...
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