# UCSB ECE 152A - EXAMPLE FINAL EXAM (9 pages)

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## EXAMPLE FINAL EXAM

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- Pages:
- 9
- School:
- University of California, Santa Barbara
- Course:
- Ece 152a - Digital Design Principles

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Department of Electrical Computer Engineering University of California Santa Barbara ECE 152A Summer 2011 Shynk H O 21 EXAMPLE FINAL EXAM INSTRUCTIONS 1 This exam is open book and open notes 2 It consists of 4 problems and is worth a maximum of 100 points The problems are not of equal difficulty so use discretion in allocating your time Answer all questions in any order 3 Show your answers in the spaces and additional pages provided and use the back side of the exam pages if you need additional work space Show your reasoning and the essential steps clearly and concisely Last Name First Name 1 ECE 152A Summer 2011 1 MULTIPLEXERS AND DECODERS 25 points Consider the following function f x1 x2 x3 x4 X m 0 4 6 7 8 11 12 14 15 1 a Find the minimum sum of products SOP implementation for f using a Karnaugh map b Use Shannon s expansion theorem to rewrite the result in part a by expanding it in terms of x3 Sketch a circuit diagram that implements f using a 2 1 multiplexer c Starting with the result in part b use Shannon s expansion theorem to further expand f in terms of x4 Sketch a circuit diagram that implements f using a 4 1 multiplexer d Show how to implement a 4 16 decoder with inputs x1 x2 x3 x4 using two 3 8 decoders Then use this decoder along with six two input OR gates and one three input OR gate to implement f in part a Solution 2 ECE 152A Summer 2011 3 ECE 152A Summer 2011 2 STATE MINIMIZATION AND MACHINE CONVERSION 30 points Consider the following next state table for a Mealy machine with input x and output z present state A B C D E F G H x 0 E 0 A 1 C 0 B 0 D 1 C 0 H 1 C 1 x 1 D 0 F 0 A 1 A 0 C 0 D 1 G 1 B 1 a Use partitioning to generate a reduced state machine Hint The minimal Mealy machine has five states Use A B C D E to label the reduced set of states b Use an implication table to obtain the same set of reduced states Clearly indicate your steps Give the state table for the reduced Mealy machine c Convert the reduced Mealy machine to the corresponding Moore machine When you split a state into two states label them numerically for example B B1 B2 Sketch the Moore state diagram Hint The minimal Moore machine has eight states Solution 4 ECE 152A Summer 2011 5 ECE 152A Summer 2011 3 SEQUENCE DETECTOR 30 points Design a finite state machine FSM with input x and output y that can recognize a sequence of four ones It should be capable of recognizing overlapping patterns of four ones thus for input 010111111010 the output of the machine is 000000111000 a Sketch a Moore state diagram for this FSM and construct the corresponding state table Hint There are five states in a minimal realization b Convert the Moore state table to a Mealy state table and reduce the number of states to four using row matching Sketch the corresponding Mealy state diagram c Using consecutive bits for the state assignment i e 00 01 10 11 derive the logic for generating the next state and the output from the present state and the input Use Q1 and Q2 to denote the most significant bit and least significant bit respectively of the present state d Implement the Mealy sequence detector using JK flip flops and sketch the circuit Solution 6 ECE 152A Summer 2011 7 ECE 152A Summer 2011 4 CMOS AND VERILOG 15 points Consider the following circuit X1 X2 f X3 a Sketch a CMOS circuit implementation of this function using a pull up pull down network b Using an always block and case statements write a Verilog module that implements this circuit Solution 8 ECE 152A Summer 2011 9

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