Computer Knowledge

Digital Logic and Microprocessors

749 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 point P in the following figure is stuck-at-1. The output f will be

$\overline{AB\bar C}$
$\bar A$
AB$\bar C$
A

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Multiple choice

A 4 bit ripple counter and a 4 bit synchronous counter are made using flip-flops having a propagation delay of 10 ns each. If the worst case delay in the ripple counter and the synchronous counter be R and S respectively, then

R = 10 ns, S = 40 ns
R = 40 ns, S = 10 ns
R = 10 ns, S = 30 ns
R = 30 ns, S = 10 ns

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Multiple choice

The minimum number of 2- to -1 multiplexers required to realize a 4- to -1 multiplexers is

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Multiple choice

In the circuit shown

Y = $\bar A\bar B + \bar C$
Y = (A +B)
Y = $(\bar A + \bar B) \bar C$
Y = AB + C

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Multiple choice

The logic function implemented by the circuit below is (ground implies logic 0)

F = AND (P,Q)
F = OR (P,R)
F = OR (P,Q)
F = XOR (P,Q

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Multiple choice

The Boolean function Y = AB + CD is to be realized using only 2-input NAND gates. The minimum number of gates required is

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Multiple choice

Directions : Two products are sold from a vending machine, which has two push buttons P1 and P2. When a button is pressed, the price of the corresponding product is displayed in a 7 - segment display. If no buttons are pressed, '0' is displayed signifying 'Rs 0'. If only P1 is pressed, '2' is displayed, signifying 'Rs. 2'. If only P2 is pressed, '5' is displayed, signifying 'Rs. 5'. If both P1 and P2 are pressed, 'E' is displayed, signifying 'Error' The names of the segments in the 7 - segment display, and the glow of the display for '0', '2', '5' and 'E' are shown below.

Consider (1) push buttons pressed/not pressed in equivalent to logic 1/0 respectively. (2) a segment glowing/not glowing in the display is equivalent to logic 1/0 respectively.

What are the minimum numbers of NOT gates and 2 - input OR gates required to design the logic of the driver for this 7 - Segment display?

3 NOT and 4 OR
2 NOT and 4 OR
1 NOT and 3 OR
2 NOT and 3 OR

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Multiple choice

The figure the internal schematic of a TTL AND-OR-OR-Invert (AOI) gate. For the inputs shown in the figure, the output Y is

0
1
AB
$\overline{AB}$

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Multiple choice

The output of the 74 series of TTL gates is taken from a BJT in

totem pole and common collector configuration
either totem pole or open collector configuration
common base configuration
common collector configuration

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Multiple choice

If X = 1 in logic equation $[X+Z{\bar Y+(\bar Z + X \bar Y ) }] \ [\bar X + \bar Z(X+Y)]$ = 1 then

Y = Z
Y = $\bar Z$
Z = 1
Z = 0

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Multiple choice

Directions : Two products are sold from a vending machine, which has two push buttons P1 and P2. When a button is pressed, the price of the corresponding product is displayed in a 7 - segment display. If no buttons are pressed, '0' is displayed signifying 'Rs 0'. If only P1 is pressed, '2' is displayed, signifying 'Rs. 2' If only P2 is pressed '5' is displayed, signifying 'Rs. 5' If both P1 and P2 are pressed, 'E' is displayed, signifying 'Error' The names of the segments in the 7 - segment display, and the glow of the display for '0', '2', '5' and 'E' are shown below.

Consider (1) push buttons pressed/not pressed in equivalent to logic 1/0 respectively. (2) a segment glowing/not glowing in the display is equivalent to logic 1/0 respectively.

If segments a to g are considered as functions of P1 and P2, which of the following is correct?

g = $\overline P_1$+ P₂, d = c + e
g = P₁+ P₂, d = c + e
g = $\overline P_1$+ P₂, e = b + c
g = P₁+ P₂, e = b + c

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Multiple choice

An 8085 assembly language program is given below. Line 1: MVI A, B5H 2: MVI B, 0EH 3: XRI 69H 4: ADD B 5: ANI 9BH 6: CPI 9FH 7: STA 3010H 8: HLT

The contents of the accumulator just after execution of the ADD instruction in line 4 will be

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Multiple choice

Two D flip-flops are connected as a synchronous counter that goes through the following Q_BQ_A sequence 00^{_{$\rightarrow$}}11^{_{$\rightarrow$}}01^{_{$\rightarrow$}}10^{_{$\rightarrow$}}00^{_{$\rightarrow$}}… The combination to the inputs D_A and D_B are

D_A = Q_B ; D_B = Q_A
D_A = ^{$\overline Q_A$}; D_B = ^{$\overline Q_B$}
D_A = ^{$(Q_A \bar Q_B + \bar Q_A Q_B)$}; D_B = ^{$\bar Q_A$}
D_A = ^{$(Q_A Q_B + \overline {Q_A Q_B})$}; D_B = ^{$\overline Q_B$}

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Multiple choice

The state transition diagram for the logic circuit shown is

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Multiple choice

The circuit shown in figure has 4 boxes each described by inputs P, Q, R and outputs Y, Z with Y = P $\oplus$Q $\oplus$R Z = RQ + $\bar P R + Q\bar P$

The circuit acts as a

4 bit adder giving P + Q
4 bit subtractor-giving P - Q
4 bit subtractor-giving Q - P
4 bit adder giving P + Q + R

Reveal answer Fill a bubble to check yourself

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