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

2019 VI 10 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 the questions and sub-ques-
tions 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) 2's complement of (100)2 is ...................... .

(ii) Binary digits are usually contracted to ................... .

(b) Answer the following :

(i) With the help of a neat circuit diagram and truth table explain
the working of 2 input RTL NOR gate. 3

(ii) Explain the working of logic circuit used to add 3 bits with the
help of a neat diagram and truth table. 3

(c) Answer the following :

State and prove De-Morgan’s second theorem. 2

2. (a) Define the following : 2

(i) Monostable multivibrator

(ii) Super Computer.

(b) Answer the following :

(i) Eplain the working of a four bit shift register with the help of
neat logic circuit diagram. 3

(ii) Explain any three applications of microprocessor. 3

(c) Answer the following : 2

What is the difference between edge triggering and level clocking ?

3. (a) Fill in the blanks : 2

(i) The logic circuit used to add 2 bits is called ............... .

(ii) The diameter of mini floppy is ............. .

(b) Do as directed : 3

(i) Convert (64)8 to its decimal equivalent.

(ii) Convert (2879)10 to its hexadecimal equivalent.

(iii) Convert (8CB)16 to its decimal equivalent.

(c) Answer the following in detail : 5

(i) With the help of a neat circuit diagram explain the working of
Transistorised Bistable Multivibrator.

Or

(ii) Explain the working of positive edge triggered J-K flip flop with
the help of neat logic diagram.

4. (a) Answer the following in one sentence : 2

(i) What is the IC number used as a clock generator driver in 8080
A microprocessor ?

(ii) What is the output of a 2-input X-NOR gate if the two inputs
are high ?

(b) Answer the following : 3

What are impact and non-Impact printers ? State one example of each.

(c) Answer the following in detail : 5

(i) Define Modulus of a counter. Explain the working of a counter

having modulus 10 with the help of a neat logic circuit diagram.

Or

(ii) Explain the working of a 3-bit synchronous counter with the help

of neat logic circuit diagram.

5. (a) Answer the following :

(i) What are volatile and non-volatile memories ? 2

(ii) Draw the block diagram of microprocessor. 2

(iii) Why “A” to “D” and “D” to “A” are necessary in a computer

system ? 2

(iv) Explain briefly magnetic tape as a storage device. 2

(v) Draw the block diagram of a counter type “A” to “D” Convertor. 2