## MTQ About Electronic and Computer

**Questions**

- Which of the following statements is true? (correct: 2 marks, incorrect: -1 mark, don’t know: 0 marks)

i. Unconditional outputs are dependent on the present state and next state

ii. Unconditional outputs are dependent on the inputs, present state and next state

iii. Conditional outputs are only dependent on the present state

iv. Unconditional outputs are dependent on the inputs and next state

v. Conditional outputs are only dependent on the next state

vi. Unconditional outputs are only dependent on the inputs

vii. Conditional outputs are dependent on the inputs and present state

viii. Conditional outputs are dependent on the inputs and next state

ix. Unconditional outputs are only dependent on the next state

x. I don’t know - You wish to design a counter which counts through the sequence {Q1,Q0} = {0,0}; {0,1}; {1,0}; and

then repeats. Use the ASM design process to obtain Boolean equations for Q1n and Q0n. Which of

the following implement the required counter? (correct: 4 marks, incorrect: -2 marks, don’t know: 0

marks)

i. 𝑄0𝑛 = 𝑄0 , 𝑄1𝑛 = 𝑄̅̅̅1̅ 𝑄̅̅̅0̅

ii. 𝑄0𝑛 = 𝑄̅̅̅1̅ 𝑄̅̅̅0̅ , 𝑄1𝑛 = 𝑄0

iii. 𝑄0𝑛 = 𝑄̅̅̅0̅ , 𝑄1𝑛 = 𝑄1 ⨁ 𝑄0

iv. 𝑄0𝑛 = 𝑄̅̅̅1̅ , 𝑄1𝑛 = 𝑄1 ⨁ 𝑄0

v. None of the above

vi. I don’t know**ELEC1202 Problem Sheet 4 Page 2 of 4** - Consider the ASM chart shown in Fig 1. Which of the following statements is correct?

(correct: 2 marks, incorrect: -1 mark, don’t know: 0 marks)

i. It represents a Mealy machine, and will require 1 D-type flip-flop to implement

ii. It represents a Mealy machine, and will require 3 D-type flip-flops to implement

iii. It represents a Mealy machine, and will require 6 D-type flip-flops to implement

iv. It represents a Moore machine, and will require 1 D-type flip-flop to implement

v. It represents a Moore machine, and will require 3 D-type flip-flops to implement

vi. It represents a Moore machine, and will require 6 D-type flip-flops to implement

vii. I don’t know

Fig 1 - Consider the Boolean equation shown below, which were created using the ASM design process.

Which of the following statements is correct?

(correct: 2 marks, incorrect: -1 mark, don’t know: 0 marks)

𝑄0𝑛 = 𝐴̅𝐵̅ + 𝐴̅𝑄1 𝑄̅̅̅0̅ , 𝑄1𝑛 = 𝐵 𝑄̅̅̅1̅ 𝑄0 + 𝐴 𝐵 𝑄1 𝑄̅̅̅0̅ , 𝐿 = 𝐴 𝐵̅ 𝑄̅̅̅1̅ 𝑄0

i. There is 1 input and 2 outputs, and the circuit will require 1 D-type flip-flop to implement

ii. There is 1 input and 2 outputs, and the circuit will require 2 D-type flip-flops to implement

iii. There is 1 input and 2 outputs, and the circuit will require 3 D-type flip-flops to implement

iv. There are 2 inputs and 1 output, and the circuit will require 1 D-type flip-flop to implement

v. There are 2 inputs and 1 output, and the circuit will require 2 D-type flip-flops to implement

vi. There are 2 inputs and 1 output, and the circuit will require 3 D-type flip-flops to implement

vii. I don’t know

NONE

N 0

1 LIGHTS GOTO_ONE

X | N 1

0 ONE

N 0

1 LIGHTS GOTO_TWO

N 1

0 TWO

X 1 0

X 0

1 LIGHTS GOTO_ZERO

X 1 0

ELEC1202 Problem Sheet 4 Page 3 of 4 - Consider the ASM chart and timing diagram shown in Fig 2. The traces for M and N have deliberately

left blank, for you to complete. Assume that, at t=0, the system is in state ‘zero’. What logic level are

A and B? (correct: 4 marks, incorrect: -2 marks, don’t know: 0 marks)

Fig 2

i. A = 0, B = 0

ii. A = 0, B = 1

iii. A = 1, B = 0

iv. A = 1, B = 1

v. A = X, B = X

vi. I don’t know - You wish to design a 2-bit up-down counter with one input M. When M=0, the counter counts up (i.e.

it follows the sequence {Q1,Q0} = {0,0} → {0,1} → {1,0} → {1,1}; and then repeats). When M=1, the

counter counts down (i.e. it follows the sequence {Q1,Q0} = {1,1} → {1,0} → {0,1} → {0,0}; and then

repeats). Use the ASM design process to obtain Boolean equations for Q1n and Q0n. Which of the

following implement the required counter?

(correct: 6 marks, incorrect: -3 marks, don’t know: 0 marks)

i. 𝑄0𝑛 = 𝑄̅̅̅0̅ , 𝑄1𝑛 = 𝑄̅̅̅1̅ 𝑄̅̅̅0̅ 𝑀 + 𝑄̅̅̅1̅ 𝑄0 𝑀̅ + 𝑄1 𝑄0 𝑀 + 𝑄1 𝑄̅̅̅0̅ 𝑀̅

ii. 𝑄0𝑛 = 𝑀̅ 𝑄̅̅̅1̅ + 𝑀 𝑄1 , 𝑄1𝑛 = 𝑀̅ 𝑄0 + 𝑀 𝑄̅̅̅0̅

iii. 𝑄0𝑛 = 𝑄̅̅̅0̅ , 𝑄1𝑛 = 𝑄̅̅̅1̅ 𝑄̅̅̅0̅ 𝑀̅ + 𝑄1 𝑄0 𝑀

iv. 𝑄0𝑛 = 𝑄0 𝑀 + 𝑄1 𝑄̅̅̅0̅ + 𝑄1 𝑀 , 𝑄1𝑛 = 𝑄̅̅̅0̅

v. 𝑄0𝑛 = 𝑄̅̅̅0̅ 𝑀̅ + 𝑀 𝑄1 , 𝑄1𝑛 = 𝑀̅ 𝑄1 + 𝑀 𝑄̅̅̅0̅

vi. 𝑄0𝑛 = 𝑄̅̅̅0̅ 𝑀̅ + 𝑀 𝑄0 , 𝑄1𝑛 = 𝑀̅ 𝑄1 + 𝑀 𝑄̅̅̅1̅

vii. None of the above

viii. I don’t know**ELEC1202 Problem Sheet 4 Page 4 of 4** - Which of the following statements is correct?

(correct: 2 marks, incorrect: -1 mark, don’t know: 0 marks)

i. A divide-by-four counter counts from 0 to 15

ii. A divide-by-five counter counts from 0 to 5

iii. A divide-by-six counter counts from 0 to 64

iv. A divide-by-seven counter counts from 0 to 6

v. A divide-by-eight counter inputs one byte of data (e.g. 01010002) and outputs the numerical

value of number divided by 8 (e.g. 000010102)

vi. I don’t know - A digital circuit is required that can detect the 2-bit binary sequence: 00, [11
*], 10, 01; where [11*]

means a sequence of one or more 11’s (note, the most significant bit is the one on the left). For

example, the following are all valid bit sequences:

00, 11, 10, 01

00, 11, 11, 10, 01

00, 11, 11, 11, 10, 01

00, 11, 11, 11, 11, 11, 10, 01

00, 11, 11, 11, 11, 11, 11, 10, 01

… etc

The binary sequence is inputted to your system via the inputs A (least significant bit) and B (most

significant bit). Assume that the binary sequence is clocked using the same clock as your circuit. The

output L should be asserted for one clock cycle every time that the sequence is detected. Use the

ASM design process to obtain Boolean equations. Which of the following equations correctly

implement the specification? Note – if you get stuck you may wish to try and ‘reverse engineer’ the

ASM from the equations.

(correct: 10 marks, incorrect: -5 marks, don’t know: 0 marks)

i. 𝑄0𝑛 = 𝐴 𝐵̅ + 𝐴̅𝑄1 𝑄̅̅̅0̅ , 𝑄1𝑛 = 𝐴 𝐵 𝑄̅̅̅1̅ 𝑄0 + 𝐵 𝑄1 𝑄̅̅̅0̅ , 𝐿 = 𝐴̅𝐵̅ 𝑄1 𝑄0

ii. 𝑄0𝑛 = 𝐴̅𝐵̅ + 𝐴̅𝑄1 𝑄̅̅̅0̅ , 𝑄1𝑛 = 𝐴 𝐵 𝑄̅̅̅1̅ 𝑄0 + 𝐵 𝑄1 𝑄̅̅̅0̅ , 𝐿 = 𝐴 𝐵̅ 𝑄1 𝑄0

iii. 𝑄0𝑛 = 𝐴̅𝐵̅ + 𝐴̅𝑄1 𝑄̅̅̅0̅ , 𝑄1𝑛 = 𝐵 𝑄̅̅̅1̅ 𝑄0 + 𝐴 𝐵 𝑄1 𝑄̅̅̅0̅ , 𝐿 = 𝐴 𝐵̅ 𝑄̅̅̅1̅ 𝑄0

iv. 𝑄0𝑛 = 𝐴 𝐵̅ + 𝐴̅𝐵 𝑄1 𝑄̅̅̅0̅ , 𝑄1𝑛 = 𝐴 𝐵 𝑄̅̅̅1̅ 𝑄0 + 𝐴 𝑄1 𝑄̅̅̅0̅ , 𝐿 = 𝐴 𝐵̅ 𝑄̅̅̅1̅ 𝑄0

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