# Unit 2 (DE)

# Theory

## Quiz 1

What is the function of an enable input on a multiplexer chip?

to apply Vcc

to connect ground

to active the entire chip

to active one half of the chip

**to active the entire chip**

The flip flops are activated by **_** trigger

Only positive edge

Only negative edge

Either positive or negative edge

None of the above

**Either positive or negative edge**

The combinational circuit have **__** number of stable states

1

2

3

4

**2**

When the clock input is low in a D flip flop then the input of the D flip flop is________

High

LOW

No Effect

None of the above

**No Effect**

In a comparator, if we get input as A>B then the output will be **__**

1

0

A

B

**1**

## Quiz 2

When toggle condition occurs in JK flip flop?

J=1, K=1

J=0, K=0

J=1, K=0

J=0, K=1

**J=1, K=1**

When reset is high and set is low in a NOR D-latch table then the output will be *__*

No change

High

Low

Invalid

**Low**

The shift registers are categorized into ________types.

1

2

3

4

**4**

## Surprise Test

The output of a sequential circuit depends on **_**.

only its input

only its state

its states and input

Decision of the designer

**its states and input**

Who invented first flip flop?

F.W. Jordan

William Eccles

Harald

Both a and b

**Both a and b**

The flip flop requires *_*

More number of gates

More power

Both a and b

None of the above

**Both a and b**

When reset is high and set is low in a NOR D-latch table then the output will be *__*

No change

High

Low

Invalid

**Low**

How many inputs does the RS latch have?

One input

Two inputs

Three inputs

Four inputs

**Two inputs**

There are total **__** steps for flip flop conversions

1

2

4

5

**5**

When toggle condition occurs in JK flip flop?

J=1, K=1

J=0, K=0

J=1, K=0

J=0, K=1

**J=1, K=1**

The flip flop is a ** _** device.

Unstable

Bi-stable

Both a and b

None of the above

**Bi-stable**

How many inverters does the basic latch consists of?

1

2

3

4

**2**

The shift registers are categorized into ________types.

1

2

3

4

**4**

The flip flops works with *__*

Binary inputs

Clock signal

Both a and b

None of the above

**Both a and b**

How many possible conversions are there to convert SR flip flop to other flip flops?

1

2

3

4

**3**

# Practical

## 2.1

If A, B and C are the inputs of a full adder then the carry is given by *__*

A AND B OR (A OR B) AND C

A OR B OR (A AND B) C

(A AND B) OR (A AND B)C

A XOR B XOR (A XOR B) AND C

**A AND B OR (A OR B) AND C**

How many AND, OR and EXOR gates are required for the configuration of full adder?

1, 2, 2

2, 1, 2

3, 1, 2

4, 0, 1

**2, 1, 2**

Half-adders have a major limitation in that they cannot *__*

Accept a carry bit from a present stage

Accept a carry bit from a next stage

Accept a carry bit from a previous stage

Accept a carry bit from the following stages

**Accept a carry bit from a previous stage**

In parts of the processor, adders are used to calculate **__**

Addresses

Table indices

Increment and decrement operators

All of the Mentioned

**All of the Mentioned**

In which operation carry is obtained?

Subtraction

Addition

Multiplication

Both addition and subtraction

**Addition**

The difference between half adder and full adder is *__*

Half adder has two inputs while full adder has four inputs

Half adder has one output while full adder has two outputs

Half adder has two inputs while full adder has three inputs

All of the Mentioned

**Half adder has two inputs while full adder has three inputs**

## 2.2

Two input MUX have_________ select lines.

1

2

3

4

**1**

MUX is also known as

Coder

Parallel Adder

Data Selector

Gates

**Data Selector**

What is the expression for the sum(s) of a half adder if the inputs are A & B?

S = A OR B

S = A AND B

S = A XNOR B

S = A XOR B

**S = A XOR B**

While implementing NOT gate using 2:1 MUX, the two inputs will be_________

A=0 & B=1

A=1 & B=1

A=0 & B=0

A=1 & B=0

**A=1 & B=0**

To implement NOR gate using MUX, **___** 2:1 will be required.

2

3

4

5

**2**

If enable input is high then MUX is ** __**–

Enable

Disable

Saturation

High Impedance

**Disable**

## 2.3

Which method of combination circuit implementation is widely adopted with maximum output functions and minimum requirement of ICs?

Multiplexer Method

Decoder Method

Encoder Method

Parity Generator Method

**Decoder Method**

Why are the lines specifically used for connecting two or more IC packages in accordance to its application in decoder circuit?

It allows the reduction of digital function into similar function with more inputs & outputs

It allows the expansion of digital function into similar function with more inputs & outputs

It allows the reduction of digital function into different function with more inputs & outputs

It allows the expansion of digital function into different function with more inputs & outputs

**It allows the expansion of digital function into similar function with more inputs & outputs**

Which of the following represents a number of output lines for a decoder with 4 input lines?

15

16

17

18

**16**

Decoders and Encoders are doing the reverse operation?

True

False

**True**

A decoder can be used as a demultiplexer by?

tying all enable pins LOW

tying all data-select lines LOW

tying all data-select lines LOW

using the input lines for data selection and an enable line for data input

**using the input lines for data selection and an enable line for data input**

The input at the 1, 2, 4, 8 inputs to a 4-line to 16-line decoder with active-low outputs is 1110. As a result, output line 7 is driven LOW?

True

False

**False**

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