# hw6s - ENGRD2300: Introduction to Digital Logic Fall 2008...

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ENGRD2300: Introduction to Digital Logic Fall 2008 Homework 6 Solutions Problem 1. Design a state machine that will toggle its output whenever a push button attached to its input is pushed and released. Assume the push button is active low. The output should toggle (change from T to T’) when the pushbutton is pressed, but should not toggle again until the button is released and pressed again. Here is a sample waveform showing the desired behavior. a) Draw a state diagram for your state machine. Moore State Machine Mealy State Machine b) Create a state/output table for your state machine. Moore State Machine X S 0 1 Z A B A 0 B B C 1 C D C 1 D D A 0 S* A [0] B [1] C [1] P P’ P P’ D [0] P P’ P’ P A B C D P’/1 P/1 P’/0 P/0 P’/1 P/1 P’/0 P/0 1

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ENGRD2300: Introduction to Digital Logic Fall 2008 Mealy State Machine X S 0 1 A B/1 A/0 B B/1 C/1 C D/0 C/1 D D/0 A/0 S* c) Is your state machine a Moore or Mealy machine? Why did you pick one over the other? Either type of state machine is an acceptable answer for this problem. However, if you look closely at the timing diagram, you will see that the T output changes when (actually just after, but you can’t see that in the example timing diagram) the P input changes. The only way to get that behavior is to use the Mealy machine. 2
ENGRD2300: Introduction to Digital Logic Fall 2008 Problem 2. Design a state machine with a 1-bit input A and a 2-bit output N, where N is the number of 1’s in the last three inputs. Here is a sample waveform showing the desired behavior.

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## This note was uploaded on 05/09/2009 for the course ENGRD 2300 taught by Professor Albonesi/long during the Fall '07 term at Cornell University (Engineering School).

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hw6s - ENGRD2300: Introduction to Digital Logic Fall 2008...

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