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S308 05/10/
THE MANCHESTER METROPOLITAN UNIVERSITY
FACULTY OF SCIENCE AND ENGINEERING
DEPARTMENT OF ENGINEERING AND TECHNOLOGY
SESSION 2003/
Examination for the BEng (HONS) ELECTRICAL ENGINEERING HND ELECTRONIC ENGINERING YEAR/STAGE ONE
UNIT 64EE1103 : DIGITAL ELECTRONICS
Tuesday 25 May 2004
2.00 pm to 4.00 pm
Instructions to Candidates
Answer FOUR questions.
Separate answer sheets are provided for use with Questions 1, 2 and 3. These should be handed in with your answer books if you choose to answer these questions.
- A digital system is defined by the truth table below. It has four inputs (S3,S2,S1,S0) and two outputs (X,Y).
S3 S2 S1 S0 X Y
0 0 0 1 1 X
0 0 1 1 1 X
0 1 0 1 1 X
0 1 1 1 1 X
(a) Label the Karnaugh maps shown in figure 1. [5]
(b) Map each output. [5]
(c) Derive the minimised equations for each output. [10]
(d) Complete the circuit diagram (figure 2) using the minimum number of gates. [5]
he data would be changing at the same time as the clock it is not possible to predict the Q output, it could be logic one or a logic zero
- An RS flip flop, shown below, is initially at the condition R=S =0 AND P=Q=1.
The inputs R and S are then changed in the sequence shown the table below.
SEQUENCE R S
initially 0 0 1 1 0 2 1 1 3 0 1 4 0 0
(a) Label the Karnaugh map (figure 4) and complete for QP. [10]
(b) Show the input sequence on the Karnaugh map. [10]
(c) Identify the stable states that the sequence passes through. [5]
R
S
Q
P
p
q
- (a) An odd parity system receives the following code groups:
FFFFh, FFFEh, 0001h.
The following code groups are BCD with even parity bits to the left of the MSB.
10001BCD, 00000BCD, 11001BCD
(b) Determine which of the six groups are in error. [6]
(c) Design circuits for the following two functions describing in detail how each works. (i) A comparator circuit that compares two binary numbers of two bits each and produces a HIGH output if the two numbers are equal. [7] (ii) A four bit Binary to Gray code converter. [7]
(d) If an X-OR gate is not available for a particular circuit show how other basic logic gates could be applied to produce the same function. [5]
