# Online Electronics and Communication Engineering Test - Digital Electronics Test 2 Loading Test...

Instruction:

• This is a FREE online test. DO NOT pay money to anyone to attend this test.
• Total number of questions : 20.
• Time alloted : 30 minutes.
• Each question carry 1 mark, no negative marks.
• DO NOT refresh the page.
• All the best :-).

1.

An 8 bit data is to be entered into a parallel in register. The number of clock pulses required is

A.
 8 B.
 4 C.
 2 D.
 1 Explanation:

In a parallel in register only one pulse is needed to enter data.

2.

When microprocessor processes both positive and negative numbers, the representation used is

A.
 l's complement B.
 2's complement C.
 signed binary D.
 any of the above Explanation:

2's complement representation requires simple electronic circuitry.

3.

For the logic circuit of the given figure the simplified Boolean expression is A.
 A + BC B.
 A + BC C.
 A + B C D.
 A + BC Explanation: = A + BC.

4.

718 = __________ .

A.
 1110002 B.
 1110012 C.
 1000012 D.
 1100012 Explanation:

71 in octal = 7 x 8 + 1= 57 in decimal = 111001 in binary.

5.

In the TTL circuit in the figure, S2 to S0 are select lines and X7 to X0 are input lines. S0 and X0 are LSBs. The output Y is A.
 Indeterminate B.
 A ⊕ B C.
 A ⊕ B D.
 C . A ⊕ B + C . (A ⊕ B) Explanation:

The MUX is made up of TTL circuit. For TTL circuit open terminal is taken high, since S2 select line is connected to OR gate whose one terminal connected to C and the other is open (high) so OR gate output is S2 = 1 + C = 1.

```S2 = 1 S1(B) S0(A)  Y
1       0     0     0
1       0     1     1
1       1     0     1
1       1     1     0```

Y = S0⊕S1 => A⊕B.

6.

How many JK flip-flops are needed to make a 4-bit shift register?

A.
 2 B.
 4 C.
 6 D.
 8 7.

A compiler is a software programme which

A.
 change high level Programming language into low level machine language B.
 change the program into binary form C.
 assembles the program D.
 executes the program 8.

A.
 two, three B.
 three, four C.
 four, six D.
 two, four 9.

A 555 timer can be used as

A.
 an astable multivibrator B.
 monostable multivibrator C.
 frequency Divider only D.
 any of the above 10.

The Boolean function A + BC is reduced form of

A.
 AB + BC B.
 AB + ABC C.
 (A + B) (A + C) D.
 (A + C)B 11.

In a Karnaugh map for an expression having 'don't care terms' the don't cares can be treated as

A.
 0 B.
 1 C.
 1 or 0 D.
 none of the above 12.

Which of the following is coincidence logic circuit?

A.  B.  C.  D.  13.

The circuit in the given figure is A.
 half adder B.
 full adder C.
 half subtractor D.
 full subtractor 14.

A.
 two 4-bit binary numbers B.
 four 6-bit binary numbers C.
 four 8-bit binary numbers D.
 any number of 4-bit numbers 15.

Mark the false statement:

A.
 since wave-shape of a digital signal is unimportant, linear amplifiers are not required B.
 the precise amplitude of a digital signal is also unimportant provided two voltage levels (0 and 1) are quite different C.
 the leading and trailing edges of a digital signal need not be sharp D.
 actual digital waves have rise and fall times of the order of a few nano seconds 16.

The address to which a software or hardware restart branches is known as

A.
 Vector location B.
 SID C.
 SOD D.
 TRAP 17.

Consider the following digital circuits: 1. Multipliers
3. D-latch
4. Circuits as shown
Which of these come under the class of combinational circuit?

A.
 1 and 2 B.
 3 and 4 C.
 1, 2 and 3 D.
 1, 2, 3 and 4 18.

A 16 x 8 ROM stores these words in its first four locations, as given below. Which of this represents 3 CH in hexadecimal?

A.
 R0 = 1110 0010 B.
 R1 = 0101 0111 C.
 R2 = 0011 1100 D.
 R3 = 1011 1111 19.

What is the maximum output voltage from the 741 op-amp?

A.
 Zero B.
 Approximately 1 V C.
 Approximately 3 V D.
 Approximately 5 V 20.

Assuming accumulator contain A 64 and the carry is set (1). What will register A and (CY) contain after ACI 0 A4 H?

A.
 4 AH, 0 B.
 4 AH, 1 C.
 4 BH, 0 D.
 4 BH, 1 