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Professor Miller, Manchester Metropolitan University, Electrical Engineering, Digital Electronics, 2004 2005 Exam, most significant bit ,output,Karnaugh map,minimised logic equation, stable state,RS flip flop,NAND gates,ring counter,multiplexer,encoder,microcontroller,I/O.
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Examination for the BEng (HONS) ELECTRICAL AND ELECTRONIC ENGINEERING HND ELECTRONIC ENGINEERING YEAR/STAGE ONE
Thursday 19 May 2005
9.30 am to 11.30 am
Instructions to Candidates
Answer FOUR out of the six questions.
(a) If s2 is the most significant bit and s0 the least, redraw the table below in your answer book and show all the possible inputs starting from
S2 S1 S0 Green Amber Red 0 0 0 0 0 0 0 0 1 1 0 0 0 1 0 1 0 0 0 1 1 1 0 0 1 0 0 0 1 0 1 0 1 0 1 0 1 1 0 0 1 1 1 1 1 0 0 1
(b) The system is to have three outputs – Red, Amber and Green. (All active high.) If none of the sensors read zero (000) then all outputs are off. If the sensors read 1, 2 or 3 only the green output is on. Sensor values of 4, 5 and 6 activates the amber output. Sensor values of 6 and 7 activate the red output. Show this on your truth table from part (a). [2]
(c) Draw a Karnaugh map for each output in your answer book. The tables should be laid out as below: [12]
(d) State the minimised logic equation for each output underneath each map. [9]
14/02/2005 continued
(b) Plot both outputs on one Karnaugh map. [5]
(c) Define what is meant by the term stable state. [3]
(d) Indicate the stable states on the map. [5]
(e) Assume R=0 and S=0 and the outputs are stable. Show on the Karnaugh map, the transitions to a stable state if S is changed to a 1. [3]
(f) Explain why the condition R=S=1 in the truth table below occurs. [4]
0 0 No change 0 1 set 1 0 reset 1 1?
(b) Why is this shift register considered to be a counter? [2]
(c) Draw a table to show the bit sequence for all states. [5]
(d) Describe the operation of the counter. [4]
(e) How could you alter this circuit to produce a ring counter? [3]
(f) How many states would the ring counter now have? [3]
14/02/2005 continued
(b) Add an even parity bit to the 8 bit code for 34BCD. [2]
(c) Design a circuit for a comparator circuit that compares two binary numbers of four bits each and produces a HIGH output if the two numbers are equal describing in detail how it works. [6]
(d) Describe a suitable system for a position encoder on a shaft that uses four sensors. Design the circuit. [8]
(e) Convert 111001$1101 2 to base-10 showing all calculations. [2]
(f) Convert 8.96875 10 to binary showing all calculations. [2]
(g) Show the steps involved for digital system to add 1 to 01101001BCD. [2]
(a) With the aid of a block diagram show the design of the embedded microprocessor system. Provide for interconnection to other remote microcontrollers. [10]
(b) State the function of the major components. [5]
(c) Explain how an interrupt driven I/O differs from a polled I/O. [2]
(d) Explain the purpose of a PPI. [2]
(e) Describe the advantage of DMA, and give an example of a type of transfer for which it is typically used. [3]
(f) Explain the difference between a dedicated I/O port and a memory mapped I/O port. [2]
(g) Explain what is meant by fan-out. [1]
