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CSE120 Hardware Lab 4

# CSE120 Hardware Lab 4 - 1.0 Introduction In this lab I...

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1.0 Introduction In this lab, I constructed a vending machine controller circuit based upon a given and assumed design specification. The objective of the lab was to gain experience using medium- scale-integrated circuit to build a controller and to gain the appreciation of using this type of design to simply the way I would build larger circuits. I was also supposed to gain experience using a proper design process and learn how simulation is necessary in prototyping circuits. After the completion of the lab, I will understand how a 4-bit magnitude comparator, a 4-bit binary adder, and a quad D flip-flop work. I will also understand to use function definition tables to build and design MSI circuits, simulate a circuit using design software prior to building the circuit, and using these things to understand the design process. 2.0 4-Bit Vending Machine Controller Circuit 1. Function and Testing of the Controller Circuit and Design Specification Prior to doing anything else, I tried to understand the design specification for this vending machine controller circuit. This helped to understand how the input and outputs should behave when they change values. Below is a list of the design specifications that were given to me and well as some that were assumed to be necessary in well-defining the problem given. Design Specifications for 4-Bit Vending Machine Controller Vending machine controller only dispenses one type of product Product will be vended for \$.30, but the machine needs to be able to have the functionality to raise this price The price value of this product will be represented by \$.05 being equal to a 1 in binary The price increases will come in \$.05 increments with a maximum price going up to \$.75 because the price will be set with a 4-bit binary number, with a maximum value of 1111, or 15 in decimal The user needs to be able to request their money back if they change their mind The design needs to provide an output signal to enable the money return The design also needs to provide an output signal when the vending mechanism is enabled The machine does not offer change Each input, nickel, dime, or quarter, is a digital 0 or 1, only of these inputs can be active high at a given time These design specifications helped me better understand the input and output needs of the vending machine. Below is a list of all input and output values and a brief description of how they affect the operation of the controller. Inputs Price: the price input is a 4-bit binary value that will be compared to the current tally of coins that has been inputted in the machine

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0 1 Nickel 0 1 Dime 0 1 Quarter GND B2 B3 B4 B1 A4 A3 A2 A1 4 3 2 1 C0 C4 283 7 5 3 14 12 6 2 15 11 4 1 13 10 9 Adder CLK CLR 175 QA QB QC QD A B D C QA QB QC QD 9 1 4 5 12 13 2 3 7 6 10 11 15 14 Register CLK 0 0 1 Product Selected 0 1 Coin Return B1 B2 B3 B0 A3 A2 A1 A0 A>B A=B A<B 85 A>Bin A<Bin A=Bin 10 12 13 15 9 11 14 1 2 3 4 7 6 5 Comparator 0 1 2 3 4 5 6 7 8 9 A B C D E F Price +5V Current Tally of 5-Cent Increments
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