Some Microcontroller important MCQ's questions for university exams, Placements, companies exams, GATE and other exams preparations with answers.
1) Which pin/signal of ADC AD571 interfacing apprises about the accomplishment of data reading
in the microcontroller so as to indicate ADC to get ready for the next data sample?
a. BLANK /CONVERT (high)
b. BLANK/DR (low)
c. DATA READY (DR)
d. All of the above
ANSWER: BLANK /CONVERT (high)
2) Which factors indicate the necessity of sample and hold circuit in the process of analog-todigital conversion?
a. Instantaneous variation in an input signal
b. Analog-to-digital conversion time
c. Both a & b
d. None of the above
ANSWER: Both a & b
3) Where do the power gets dissipated during the gradual decay of an inductor current (upto zero
value) by turning OFF the transistor in an electromechanical relay?
a. Internal resistance of the coil
b. Internal Diode resistance
c. Both a & b
d. None of the above
ANSWER: Both a & b
4) Which diodes are employed in the electromechanical relays since the inductor current cannot be
reduced to zero?
a. Tunnel Diode
b. Shockley Diode
c. Freewheeling Diode
d. Zener Diode
ANSWER: Freewheeling Diode
5) In an electromechanical relay, the necessity of connecting an external base resistance arises
only _________
a. in the presence of an internal pull-up resistor
b. in the absence of an internal pull-up resistor
c. in the absence of an internal push-up resistor
d. in the presence of an internal push-up resistor
ANSWER: in the absence of an internal pull-up resistor
6) What is the correct chronological order/sequence of steps associated with the latch operations
given below?
a. Loading the data on output port
b. Increment in the digital output functions by using microcontroller pins
c. Application of latch enable signal to desired latch
a. A, B, C
b. A, C, B
c. C, A, B
d. B, A, C
ANSWER: A, C, B
7) How is the latch interfacing with the microcontroller related to the number of digital output
functions?
a. It increases the number of digital output functions in a time multiplexed manner
b. It decreases the number of digital output functions in a time multiplexed manner
c. It increases the number of digital output functions in a frequency multiplexed manner
d. It decreases the number of digital output functions in a frequency multiplexed manner
ANSWER: It increases the number of digital output functions in a time multiplexed manner
8) What happens when the latch is kept open once after the execution of the latch operation by
allowing input digital data byte to appear at the output?
a. Variation in an input digital data
b. Output data remains constant despite changing input digital data
c. Variation in an output data with respect to input data variation
d. Cannot predict
ANSWER: Output data remains constant despite changing input digital data
9) Which ports assist in addressing lower order and higher address bytes into the data bus
simultaneously, while accessing the external data memory?
a. Port 0 & Port 1 respectively
b. Port 1 & Port 2 respectively
c. Port 0 & Port 2 respectively
d. Port 2 & Port 3 respectively
ANSWER: Port 0 & Port 2 respectively
10) Which among the below mentioned memory components possessess the potential of generating
an ALE signal for the latching purpose of lower address byte in an external data memory?
a. CPU
b. Data Bus
c. Port 0
d. Port 1
ANSWER: CPU
11) What happens when the RD signal becomes low during the read cycle?
a. Data byte gets loaded from external data memory to data bus
b. Address byte gets loaded from external data memory to address bus
c. Data byte gets loaded from external program memory to data bus
d. Address byte gets loaded from external program memory to address bus
ANSWER: Data byte gets loaded from external data memory to data bus
12) Which bus/es acquire/s the potential of liberally receiving the code byte after addressing the
lower order address byte?
a. Data bus
b. Address bus
c. Both a & b
d. None of the above
ANSWER: Data bus
13) Which essential operation should be performed while reading the external program byte on the
data bus?
a. Latching of lower address byte
b. Latching of higher address byte
c. Latching of any addressable byte irrespective of priority level
d. None of the above
ANSWER: Latching of lower address byte
14) Which pin should be set low along with the program counter contents more than 0FFFH for
accessing the external program memory?
a. EA
b. ALE
c. PSEN
d. All of the above
ANSWER: EA
15) What value of 'B' should be loaded in the TRISB register if return lines (RB7:RB4) and RB3:RB0
are supposed to be inputs and outputs respectively after the PORT B initialization?
a. 11000100
b. 11110011
c. 11110001
d. 11110000
ANSWER: 11110000
16) Which keys are encoded for scan lines with '1101' value (RB1 low) condition?
a. 0, 4, 8, C
b. 1, 5, 9, D
c. 2, 6, A, E
d. 3, 7, B, F
ANSWER: 2, 6, A, E
17) Which lines are driven low under the software control during interfacing HEX keyboard with PIC
16F877?
a. Scan Lines
b. Return Lines
c. Both a & b
d. None of the above
ANSWER: Scan Lines
18) What is the purpose of using Schmitt Trigger in the hardware circuit for key debouncing?
a. Noise Elimination
b. Improvement in Noise Immunity
c. Increase in Noise Figure
d. Reduction in Noise Temperature
ANSWER: Improvement in Noise Immunity
19) Which is the an alternative mechanism of preventing the software to be dependent on several
delay factors along with an optimum time proficiency of checking LCD status at the interfacing level?
a. Polling of DB7 bit of the data bus
b. Updating the faster display in less time
c. Generalization of clock frequency and display module
d. All of the above
ANSWER: Polling of DB7 bit of the data bus
20) How many data lines are essential in addition to RS, EN and RW control lines for interfacing LCD
with Atmel 89C51 microcontroller?
a. 3
b. 5
c. 8
d. 10
ANSWER: 8
21) On which factors do the delay between two characters depend for display purposes in LCD?
a. Clock frequency
b. Display module
c. Both a & b
d. None of the above
ANSWER: Both a & b
22) How much delay is necessarily provided after the power-on-reset condition in order to overcome
the predicaments related to valid power supply levels assigned to microcontroller and LCD?
a. 10 ms
b. 12 ms
c. 15 ms
d. 25 ms
ANSWER: 15 ms
23) Match the HEX codes of LCD with their associated functions
a. 10H ----------------- 1) Shifting of cursor position to right
b. 14H ----------------- 2) Shifting of cursor position to left
c. 18H ----------------- 3) 2 lines & 5 x 7 character font
d. 38H ----------------- 4) Shifting of an entire display to the left
a. A-4, B–1, C-2, D-3
b. A-3, B–2, C-1, D-4
c. A-2, B-1, C-4, D-3
d. A-1, B–2, C-3, D-4
ANSWER: A-2, B-1, C-4, D-3
24) How does the instruction execute for read command 'Get LCD Status' in LCD?
a. By allowing EN line to go from low to high
b. By allowing EN line to go from high to low
c. By maintaining EN line to be stable
d. None of the above
ANSWER: By allowing EN line to go from high to low
25) When can a LCD display the text form of data?
a. only when RS line is high
b. only when RW line is high
c. only when RS line is low
d. only when RW line is low
ANSWER: only when RS line is high
26) The display operations in LCD are undertaken on EN line with ______
a. 0 to 1 transitions
b. 1 to 0 transitions
c. Both a & b
d. None of the above
ANSWER: 1 to 0 transitions
27) Which control line/s act/s as an initiator by apprising LCD about the inception of data
transmission by the microcontroller?
a. Enable (EN)
b. Register Select (RS)
c. Read/Write (RW)
d. All of the above
ANSWER: Enable (EN)
28) What does the availability of LCD in 16 x 2 typical value indicate?
a. 16 lines per character with 2 such lines
b. 16 characters per line with 2 such lines
c. 16 pixels per line with 2 such sets
d. 16 lines per pixel with two such sets
ANSWER: 16 characters per line with 2 such lines
29) Which among the below given assertions exhibits the dependency of LED status over them,
especially for LED and push button connection?
a. Closure of pushbutton
b. Low Output pin driven by microcontroller
c. Both a & b
d. None of the above
ANSWER: Both a & b
30) What is the possible range of current limiting resistor essential for lightening the LED in certain
applications after pressing the push-button?
a. 25-55 Ω
b. 55-110 Ω
c. 110-220 Ω
d. 220-330 Ω
Answer: 220-330 Ω
