The "Gottcha Anti-Theft" Machine There are many anti-theft devices on the market that attempt to foil a would-be robber from starting your car and driving off with it. One popular item has a keypad like a touch-tone telephone. In order to start your car, you must key in a secret four digit decimal code, such as '3719'. It only "remembers" the most recent four digits you have keyed in. Thus the sequence '3723719' will let you start your car. For simplicity here we use a code based on a sequence of eight bits, and use two push buttons to enter a sequence serially. Each press of a button enters the corresponding digit. Figure 1. The Gottcha machine in action. As you key in the bits in sequence, the device outputs E = 0 until the most recent eight bits agree with a built-in secret code byte. Then E switches to 1. The shut-off gottcha: If 16 bits are toggled in without the secret code being observed, the system shuts off and won't accept any more bits. Add a reset button to the system that presumably only the owner could control: when RESET is pressed the system is again enabled and can accept bits. Design and test (on LogicWorks) the miracle Gottcha machine. Do this in two different ways (thus designing and simulating two different circuits): Factory Preset Model Secret Code: 10100011

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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The "Gottcha Anti-Theft" Machine There are many anti-theft devices on the market that attempt to foil a would-be robber from starting your car and driving off with it. One popular item has a keypad like a touch-tone telephone. In order to start your car, you must key in a secret four digit decimal code, such as '3719'. It only "remembers" the most recent four digits you have keyed in. Thus the sequence '3723719' will let you start your car. For simplicity here we use a code based on a sequence of eight bits, and use two push buttons to enter a sequence serially. Each press of a button enters the corresponding digit. Figure 1. The Gottcha machine in action. As you key in the bits in sequence, the device outputs E = 0 until the most recent eight bits agree with a built-in secret code byte. Then E switches to 1. The shut-off gottcha: If 16 bits are toggled in without the secret code being observed, the system shuts off and won't accept any more bits. Add a reset button to the system that presumably only the owner could control: when RESET is pressed the system is again enabled and can accept bits. Design and test (on LogicWorks) the miracle Gottcha machine. Do this in two different ways (thus designing and simulating two different circuits): Factory Preset Model Secret Code: 10100011

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