Goa Board Class 12 Question Paper Mar 2018 Digital Electronics _ Computers _New Pattern_

2018 III 14 1000 Seat No. :

Time : 2 Hours DIGITAL ELECTRONICS & COMPUTERS
(New Pattern)
Subject Code

V 3 3 1

Total No. of Questions : 5 (Printed Pages : 3) Maximum Marks : 50

INSTRUCTIONS : i) Answer each question on a fresh page.
ii) Write the number of the question and sub-question clearly.
iii) All questions are compulsory.
iv) Figures to the right indicate full marks.
v) Draw neat diagrams wherever necessary.

1. A) Fill in the blanks : [2]
i) To standardize computer hardware, industry settled on an input output code
known as
ii) The volatile memory used in computers is

i) Explain with a neat logic diagram and truth table the working of 2 input
TRL NAND gate. [3]
ii) What are non-impact printers ? Explain the working of inkjet printer in
brief. [3]

Draw the internal pin configuration diagram of quad two input NOR gate. [2]

2. A) Define the following : [2]
i) Flip-Flop
ii) Full-adder

V – 331 -1- P.T.O.

i) Draw a neat logic diagram of 4-bit shift right register using D flip-flop and
explain its working. [3]
ii) State three points of comparison between 8080A and 8085 microprocessor
with respect to the following : [3]
a) Clock phase
b) Functional chips
c) Status.

Draw the block diagram of a counter type ‘A’ to ‘D’ converter. [2]

3. A) Fill in the blanks : [2]
i) The decimal equivalent of the binary subtraction, (0101)2 – (0011)2 is
ii) The instruction set of 8080A microprocessor has ___________ number of
instructions.

B) Do as directed : [3]
i) Convert hexadecimal number (2F59)16 to its decimal equivalent.

ii) Find the decimal equivalent of (107)8.
iii) Convert the decimal number (513)10 into binary equivalent.

C) Answer the following in detail : [5]
What is a multivibrator ? With the help of a neat circuit diagram explain the
working of a monostable multivibrator.
OR

Explain the working of transistorised Schmitt trigger with the help of a neat
circuit diagram.

V – 331 -2-

4. A) Answer the following in one word : [2]
i) If you cascade three NOT gates, what kind of gate in the over all circuit
equivalent to ?
ii) Which pin carries ‘RESET OUT’ signal in 8085 microprocessor ?

B) Answer the following : [3]

Show that NOR gate is equivalent to bubbled AND gate using logic circuit and
truth table.

C) Answer the following in detail : [5]
What is modulus of counter ? Explain the working of a counter having modulus
of 10 with the help of a neat logic circuit diagram.
OR
Explain the working of a 4-bit asynchronous counter with the help of a neat
logic circuit diagram.

5. Answer the following :
i) State the diameters of mini and micro floppies. [2]

ii) Draw the circuit diagram and truth table of D-flip-flop. [2]
iii) What is ‘Accuracy’ and ‘Resolution’ in D to A converter. [2]
iv) Briefly explain hard disk as a storage device. [2]

v) Draw a neat block diagram of a typical microprocessor. [2]

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