Goa Board Class 12 Question Paper June 2018 Digital Electronics and Computers

2018 VI 11 1430 Seat No. :

Time : 2 Hours DIGITAL ELECTRONICS AND COMPUTERS

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 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) The decimal equivalent of (F)16 is ________
ii) When input signals A = 1 and B = 0 is applied to an EX-NOR gate, its
output signal will be __________

i) With a neat circuit diagram, explain 4-bit ring counter. [3]
ii) What are bubbled gates ? With the help of logic symbol and truth table,
explain bubbled OR gate. [3]

C) Answer the following : [2]
What is shift register ? Draw a neat circuit diagram of 4-bit shift right register.

2. A) Define the following : [2]
i) Full Adder
ii) Buffer Register.

V-331 -1- P.T.O.

i) Draw a neat circuit diagram of JK flip flop and explain its ‘Reset’ mode. [3]
ii) Explain the terms ‘volatile memory’ and ‘non-volatile memory’. Give one
example of each. [3]

C) Answer the following :
Draw the block diagram of counter type analog to digital converter. [2]

3. A) Fill in the blanks: [2]
i) The 1’s complement of binary number (1010)2 is _________
ii) The 8080A microprocessor consists of __________ number of functional
chips.

B) Do as directed : [3]
i) Convert (4429)10 to its octal equivalent.
ii) Convert (101100010)2 to its decimal equivalent
iii) Convert (1993)10 to its hexadecimal equivalent.

Draw a diagram of typical microprocessor and state the functions of Arithmetic
Logic Unit (ALU). [5]
OR
Draw a block diagram of computer system state any three functions of Central
Processing Unit (CPU). [5]

4. A) Answer the following in one sentence. [2]
i) What is the clock frequency of 8085 microprocessor ?
ii) Write the formula to obtain total time period of the output waveform of a
symmetrical astable multivibrator.

V-331 -2-

State Demorgan’s second theorem. Show that A.B = A + B . [3]

Explain ‘Mouse’ as an input device and ‘Plotter’ as an output device in the
computer system. [5]
OR

Explain ‘Floppy disk’ as storage device, state the diameters of mini-floppy
and micro-floppy. [5]

5. Answer the following :
i) Draw neat logic diagrams converting a NOR gate to AND gate and OR gate. [2]
ii) State any two uses of ‘Schmitt Trigger’. [2]
iii) Differentiate between ‘edge triggering’ and ‘level clocking’ with two points of
difference in flip-flops. [2]
iv) With the help of logic symbol, explain ‘multiplexer’. [2]
v) State any two advantages of binary ladder. [2]

______________

V-331 -3-