Online Digital Electronics Test - Digital Electronics Test 3

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Total number of questions: 20.
Time allotted: 30 minutes.
Each question carries 1 mark; there are no negative marks.
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Convert the Gray code 1011 to binary.

1011

1010

0100

1101

[#]

A binary number can be converted to a decimal number by summing the decimal values of the weights of all the 1s in the binary number.

True

False

[#]

12₁₀= 1101₂ = C₁₆ = 00010010 BCD

True

False

[#]

A 4-variable AND-OR circuit produces a 1 at its Y output. Which combination of inputs is correct?

A = 0, B = 0, C = 0, D = 0

A = 0, B = 1, C = 1, D = 0

A = 1, B = 1, C = 0, D = 0

A = 1, B = 0, C = 0, D = 0

[#]

The expression

can be directly implemented using only ________.

an XOR gate

an XNOR gate

an AOI circuit

three 2-input NAND gates

[#]

The pulse width of a one-shot circuit is determined by ________.

a resistor and capacitor

two resistors

two capacitors

none of the above

[#]

Synchronous binary counters can only be used for the application of timing of digital systems.

True

False

[#]

An OR gate with inverted inputs functions as:

an AND gate.

a NAND gate.

a NOR gate.

an inverter.

[#]

Subtract the following binary numbers.

0101 1000		1010 0011		1101 1110
–0010 0011		–0011 1000		–0101 0111

0011 0100 0110 1010 1000 0110

0011 0101 0110 1011 1000 0111

0011 0101 0110 1010 1000 0111

0011 0101 0110 1010 1000 0110

[#]

10.

How many BCD adders would be required to add the numbers 973₁₀ + 39₁₀?

[#]

11.

Inside a computer all arithmetic operations take place in the ________.

accumulator register

ALU

CPU

B register

[#]

12.

The major advantage of CMOS logic circuits over TTL is very low power consumption.

True

False

[#]

13.

The minimum input voltage recognized as HIGH by a TTL gate is ________.

2.0 V

2.4 V

0.8 V

5.0 V

[#]

14.

The 74139 dual four-line demultiplexer functions as a decoder if ________.

the

line is grounded

data input is on the

line

data input is on the A₀ line

the A₀ line is grounded

[#]

15.

In HDL, the operation of the DEMUX is exactly described using a ________.

function

process

variable type

number of conditional signal assignment statements

[#]

16.

In the keypad encoder, just after the 4 ms mark, the simulation initiates the release of the key by changing the column value to ________, which causes the d output to go into its Hi-Z state.

0 hex

4 hex

8 hex

F hex

[#]

17.

Determine the output voltage V_out for the circuit in the given figure.

–0.5 V

0 V

+5 V

+4.3 V

[#]

18.

What is a disadvantage of CMOS in place of TTL?

It switches slower.

It uses less power.

It is smaller.

cost

[#]

19.

Show from the truth table how an exclusive-OR gate can be used to invert the data on one input if the other input is a special control function.

Using A as the control, when A = 0, X is the same as B. When A = 1, X is the same as B.

Using A as the control, when A = 0, X is the same as B. When A = 1, X is the inverse of B.

Using A as the control, when A = 0, X is the inverse of B. When A = 1, X is the same as B.

Using A as the control, when A = 0, X is the inverse of B. When A = 1, X is the inverse of B.

[#]

20.

The RST pin requires a HIGH to reset the 8051 microcontroller.

True

False

[#]

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Online Digital Electronics Test - Digital Electronics Test 3

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