Computer Knowledge

Digital Logic and Microprocessors

735 Questions

Digital logic and microprocessors form the core of computer science, covering logic gates, combinational and sequential circuits, and CPU architecture. These topics are crucial for computer knowledge sections in technical exams. Test your digital electronics basics here.

Logic gates and circuitsCombinational vs sequential circuitsMicroprocessor instructionsTruth tables and boolean functions

Digital Logic and Microprocessors Questions

Multiple choice

The out put Y of a 2 - bit comparator is logic 1 whenever the 2 - bit input A is greater than the 2 - bit input B. The number of combinations for which the output is logic 1, is

  1. 4

  2. 6

  3. 8

  4. 10
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For a 2-bit comparator checking if A > B, we enumerate cases: A=01,B=00; A=10,B={00,01}; A=11,B={00,01,10}. This gives 1+2+3=6 combinations where output is 1. Total combinations for two 2-bit inputs is 16, but only 6 satisfy A > B.

Multiple choice

In the following circuit, the comparators output is logic “1” if V1 > V2 and is logic “0” otherwise. The D / A conversion is done as per the relation VDAC = $\sum_{n=0}^3 2^{n-1}b_n$ Volts, where b3 (MSB), b1, b2 and b0 (LSB) are the counter outputs. The counter starts from the clear state.

The magnitude of the error between VDAC and Vin at steady state (in volts) is

  1. 0.2

  2. 0.3

  3. 0.5

  4. 1.0
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The $V_{ADC} - V_in$ at steady state is = 6.5 - 6.2 = 0.3V

Multiple choice

The 8255 Programmable Peripheral Interface is used as described below. (i) An/A D converter is interface to a microprocessor through an 8255. The conversion is initiated by a signal from the 8255 on Port C. A signal on Port C causes data to be stobed into Port A. (ii) Two computers exchange data using a pair of 8255s. Port A works as a bidirectional data port supported by appropriate handshaking signals. What will be the appropriate modes of operation of 8255 Interface for (i) and (ii)?

  1. Mode 0 for (i) and Mode 1 for (ii)

  2. Mode 1 for (i) and Mode 2 for (ii)

  3. Mode for (i) and Mode 0 for (ii)

  4. Mode 2 for (i) and Mode 1 for (ii)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Multiple choice

The full form of the abbreviations TTL and CMOS in reference to logic families are

  1. Triple Transistor Logic and Chip Metal Oxide Semiconductor

  2. Tristate Transistor Logic and Chip Metal Oxide Semiconductor

  3. Transistor Transistor Logic and Complementary Metal Oxide Semiconductor

  4. Tristate Transistor Logic and Complementary Metal Oxide Silicon
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

TTL $\rightarrow$ Transistor - Transistor logic CMOS $\rightarrow$ Complementary Metal Oxide Semi-conductor