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Unformatted text preview: ELEC151  Final Examination
Open Note of One A4 Sheet Name and Student Number
Write down your name and student number on the answer bookiet. State Reduction (15%) Given a state transition diagsem below. use implication chart to determine and
draw the fuliy reduced state transition diagram. Present Next State Output
State X=0 X=1 Xeo X=1
A C E 0 0 B H G 0 1 C B A 0 O D E H 1 0 E E C 0 O F H D 0 1 G A H 1 0 H D F 0 1 State Aesignment (15%)
Given the state transition table of a Meaty machine below. a). b}. Do the state assignment by minimum bit change heuristic. How many bit_
changes are there for all transitions? (5%) Do the state assignment by state assignment guidelines. How many literals
and equivalent gate counts are in the nextvstate functions if the finite state
machine is implemented by D flipﬂops? (10%) Present Next State Output
State  X=O X=1 X=0 X=l
A A D 0 0 B A D 0 1 C B C 0 0 D A C O D Vending Machine {20%)
A vending machine will deliver a package of gum when 20 cents are deposited. The machine has a singlecoin slot for [rickets [5 cents) and dimes (10 cents). The
machine cannot produce any change. But if 25 cents were deposited, it will credit
the buyer with 5 cents and wait for the buyer to make the second purchase. a}.
b).
0). Draw a minimized state transition diagram in Moore machine. (5%) Draw a minimized state transition diagram in Meatyr machine. (5%) Do the state assignment in order (00 or [100 tor “0 cent” , 01 or 001 for
“5 cents” , 10 or 010 for “ 10 cents” , etc.) and implement this vending
machine by T flip—flops. Write down only the nextstate and output tunctions. (10%] (Either a Moore or Meaty machine can do} ELE0151 Final Exam. 16Dec1999, 1K2 Seguence Detector (15%)
Design a sequence detector which investigates an input sequence X and
produces an output 2 = 1 for any input sequence ending with "0010". Use T flip fiop for the first state [01) and JK flipflop tor the second state (00) to implement
the detector in Meaty machine and show the following: a). Minimized state diagram (5%)
b). State assignment (5%) (The best assignment gets 5, the second gets 3 and others get 1}
c). Nextstate and output logic iunctions (5%) Digital Combinational Look (15%) Design a 2bit seriai digital combinationai lock. The lock has a RESET button, an
ENTER button, and a twoposition switch to represent the key value being
entered. The RESET button is for initial start Up. The input sequence is 1) the
first key vatue, 2) ENTER, 3) the second key vaiue. and 4) ENTER. If all two key
values are correct, the UNLOCK signal is asserted. Otherwise. an ERROR signal is asserted. lmpiement this combinational look by Meaty machine with D flipflops.
51). Draw a state transition diagram. {5%} b). Draw a circuit schematic and brieﬂy explain. (10%)
(Any circuit that can serve the specification is fine) Reverse Engineering [20%)
Given a Mealy machine belowI draw its complete state transition diagram. ELEC151 Final Exam. 16Dec1999, 2 f2 ...
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 reset button, state transition diagram

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