TEE206/05 Digital Electronics (Jan 2019)
Tutor-marked Assignment 2 (TMA 2 – 25%)

Students are highly encouraged to passage their TMAs to the Turnitin system before submission, to encourage honest academic writing and it is not mandatory except for Project courses. Evidence of plagiarism or collusion will be taken seriously and the University regulations will be applied fully. You are advised to be familiar with the University’s definitions of plagiarism and collusion.
Instructions:
1. This is an individual assignment. No duplication of work will be tolerated. Any plagiarism or collusion may result in disciplinary action, in addition to ZERO mark being awarded to all involved.
2. You are to submit online of your answers in OAS system and it is your responsibility to submit your TMA correctly and timely. OAS system doesn’t allow re-submission of assignment. Marks will be awarded for correct working steps and answers.
3. The total marks for TMA 2 is 100 and contributes 25% towards the total grade.
4. TMA 2 covers the topics in Unit 1, 2, 3 and 4.
5. TMA 2 has to be done individually.
6. Your assignment must be word processed (single spacing) and clearly laid out. Any additional appendices or attachments must be placed at the end of the submitted document and must be referred to in the main body of the assignment, or it will not be read by the marker. Answer all parts in English.
7. All files or documents submitted must be labeled with your WOU ID and name.

Question 1 (20 Mark)
a) Construct a 5 bit ring counter using rising edge triggered D Flip-flops
(7 Mark)
b) Sketch the output waveform for this ring counter for two complete cycles, given that the initial value is 00001
(10 Mark)
c) Explain the weaknesses of a ring counter and suggest how weaknesses of a ring counter can be overcome?
(3 Mark)
Question 2 (20 Mark)
a) Calculate the number of SELECT Inputs necessary for a 16:1 Multiplexer.
(4Mark)
b) Explain the function of the SELECT inputs in a multiplexer.
(2 Mark)
c) Draw the Truth Table for the 16:1 Multiplexer.
(8 Mark)
d) Using the 16:1 multiplexer implement the logic function below:
F(A,B,C,D)={2,3,5,12}
(6 Mark)

Question 3 (60 Mark)-Lab
Lab Instructions:
1. The lab session consists of two labs which is Lab 1 (Decoder Circuits) and Lab 2 (Asynchronous Counter). Marks will be awarded based on the following criteria:
a) Correct results obtained from all parts practical lab work.
b) The extend of your involvement in the lab. Tutors will observe students to see if they are actively involved in the lab exercises, or do they just sit around passively and waiting for other people to do the work and copy their results.
c) Problems solving skills. Students will be observed to see if they are good at analytical thinking and problem solving when it comes to troubleshooting their circuits to make them work and to achieve the results they want.
d) How knowledgeable the students are in the subject matters. You must already possess the basic knowledge of logic circuits before you come to the lab session. So it would be prudent for you to go through your course materials, lab sheet and the NI Elvis User Manual beforehand.
e) The overall presentation of the report, how you present your data and draw appropriate conclusions on the results obtained.
2. The student version of the NI Elvis User manual is uploaded together with this TMA. Please make sure that you download it and go through it so that you will know how to use the equipment when you come to the lab.
3. Remember that the plagiarism rules apply for your lab report as well. All party caught involving in plagiarism will be awarded with ZERO mark!
4. You should always ensure the working space in the lab is tidy before, during and after the lab sessions.

Lab Exercise 1 (40 marks)
Title: Decoder Circuits
Objective: To understand usage and theory of the 7447 decoder to change binary input into decimal output with the seven segment display.
Component:
74LS47 decoder (1 Unit)
Common-Anode 7-Segment Display
470 Ohm resistor (7 pcs)
1k Ohm resistor (4 pcs)
DC Power supply
Other Equipment:
Jumper wires, NI Elvis Tester Board (optional)
Procedure:
1. Construct the circuit as shown in Figure 2. Refer to specific datasheets that will be provided by the instructor for more specific information on pins and internal circuitry of the respective ICs.
2. Have your instructor to verify the pin connections before you power up the board.
3. Observe the output on the seven-segment display and record your observations.
4. Substitute pin 7 (A), 1(B), 2 (C) and 6 (D) on the 7447 decoder chip with the following information and record all observations on the 7 segment display in a Table 2:
Table 2: Result on 7-segment display
DCBA Result on 7-segment display
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
5. Modify the circuit by connecting the Vcc to connecting to GND with 1k pull up resistors for each pin as shown in Figure 3. Substitute pin 7 (A), 1 (B), 2 (C) and 6 (D) on the 7447 decoder chip with the following information and record all observations on the 7 segment display in a Table 3:
Table 3: Result on 7-segment display
DCBA Result on 7-segment display
1111
1110
1101
1100
1011
1010
1001
1000
0111
0110
Figure 1: Overall 7446 Decoder circuit

Figure 2: Overall Schematic of the Decoder circuit for Procedure 4

Figure 3: Overall Schematic of the Decoder circuit for Procedure 5
Answer these Questions:
1. Complete the tables in procedures 4 and 5 above. You are required to include a picture of circuit output results in your report
(20 marks)
2. Write a discussion for this lab. The discussion should be as detailed as possible covering the following aspects:
a.) Illustrate the operation of the circuit in Figure 1.
b.) Describe significance and functionality of the 74LS47.
c.) Explain how binary numbers are converted to become decimal numbers using the circuit above.
d.) Explain the difference between the inputs in procedures 4 and 5.
e.) Suggest typical applications where this circuit can be found.
(20 marks)

Lab Exercise 2 (20 marks)
Title: Asynchronous Counters (using Dual JK Negative-Edge-Triggered flip-flops)

Objective:
To understand usage and theory of the Asynchronous Counters built using the JK-FF.
Component:
74LS73 Dual JK Negative-Edge-Triggered Flip-flops
LED (2 Units)
330 ? resistor (2 units)
DC Power supply
Oscilloscope with 2 probes with build-in function generator or
Oscilloscope with 2 probes with separate unit Function Generator
Other Equipment:
Jumper wires, NI Elvis Tester Board (optional)
Procedure:
1. Construct the circuit as shown in Figure 5. Refer to specific datasheets that will be provided by the instructor for more specific information on pins.
2. Connect the Q outputs of each JK-FF to an LED to observe the outputs at various times.
3. Have your instructor to verify the pin connections before you power up the board with Power supply, Vcc = 5V and Function generator Vi = 500m Hz, 0-5V (amplitude), square wave.
4. Observe the output on the LED and record your observations.


Figure 4: Pin numbering for 74LS73N

Figure 5: A 2-bit Asynchronous Counter implemented using the 74LS73N IC with labeled pin numbering

Answer these Questions:
1. What is the counting sequence of this Asynchronous Counter (You are required to include a picture of circuit output results in your report)?
(4 marks)
2. Draw the State Diagram for this circuit to show the counting sequence.
(2 marks)
3. Draw the Timing diagram for this circuit to show the counting sequence.
(2 marks)
4. Explain why PRESET and CLEAR are set to 1 throughout the experiment and J and K=1.
(2 marks)
5. What is the output frequency of the output of JK-FF A if the Function Generator is set to 1 Hz?
(2 marks)
6. Explain how 2-bit Asynchronous Counter operates in this experiment.
(4 marks)
7. Explain how 2-bit Asynchronous Counter can be modify into 4-bit Asynchronous Counter
(4 marks)
END OF TMA 2