Goa Board Class 12 Question Paper Mar 2019 Digital Electronics and Computers

2019 III 09 1000 Seat No.

Time : 2 Hours Digital Electronics & Computers

Subject Code

V 3 3 1

Total No. of Questions : 5 (Printed Pages : 4) 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) The 2’s Complement is the binary number that results when we

add 1 to the ........................... .

(ii) If A = 1 and B = 1 are given to the input of Half Adder then

their Sum is equal to ......................... .

(i) Prove A B A . B with the help of a neat logic diagram and

truth table. 3

(ii) With the help of a neat circuit diagram and truth table, explain

the working of 2 input DRL OR gate. 3

V-331 1 P.T.O.

(C) Answer the following :

Draw neat logic diagrams to obtain AND and OR gate using NOR

gates. 2

2. (A) Define the following : 2

(i) Central Processing Unit (CPU)

(ii) Cache Memory

(i) Differentiate between 8080A and 8085 microprocessor with respect

to clock frequency, interrupt lines and instruction set. 3

(ii) Explain in brief the difference between Monochrome, RGB and

Coloured Monitor. 3

(C) Answer the following :

Draw a neat block diagram of a Counter type A to D converter. 2

3. (A) Fill in the blanks : 2

(i) The expression for the frequency of oscillation for Astable

multivibrator is ....................... .

(ii) Microprocessor based computer graphics are able to display

....................... on the monitor.

V-331 2

(B) Do as directed : 3

(i) Convert (4095)10 to its hexadecimal equivalent.

(ii) Convert (4073)8 to its decimal equivalent.

(iii) Convert (10101)2 to its decimal equivalent.

(C) Answer the following in detail : 5

With the help of a neat circuit diagram explain the working of
transistorised Bistable multivibrator.

Or

Explain the working of positive edge triggered J-K Flip-Flop with a
neat diagram.

4. (A) Answer the following in one/two words : 2

(i) What is the hexadecimal equivalent of (10)10.

(ii) Write the output logic expression of EX- NOR gate.

(B) Answer the following : 3

Explain the working of a 4-bit Shift right register with the help of a

neat diagram.

(C) Answer the following in detail : 5

Explain the working of a 4-bit ripple counter with the help of a neat

diagram.

Or

With the help of a neat logic diagram explain the working of a 3-bit
ring counter.

V-331 3 P.T.O.

5. Answer the following :

(i) What do you mean by Accuracy and Resolution in D to A

converter. 2

(ii) Draw the block diagram of a microprocessor. 2

(iii) What do you mean by Volatile and Non-Volatile memory. 2

(iv) What is the difference between Edge Triggering and Level

clocking ? 2

(v) Briefly explain Laser Printer. 2

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