This set of AVR Microcontroller Interview Questions and Answers focuses on “Serial Port Communication”.
1. What actually are the DB9, DB25 ports available in our computers?
a) they are connectors used to transfer data either serially or parallelly
b) they are the RS232 connectors used to connect two incompatible devices
c) they are the TTL logic connector pins used for communication
d) they are just data transfer pins used to transfer the data
View Answer
Explanation: DB9 and the DB25 ports are the ports that are based on the RS232 logic that is basically used for communicating two incompatible devices.
2. What does RI handshaking signal refer to according to the RS232 logic?
a) if this logic is high then a receive interrupt is generated
b) this pin is high during transmission
c) this pin is high during a reception in order to tell that the device is busy at this particular time
d) none of the mentioned
View Answer
Explanation: RI pin of the RS232 logic tells us about the ring indicator i.e it sends a busy signal if the device is currently receiving any data.
3. What is the major difference between a MAX232 and a MAX233 device?
a) one has one serial port other has two
b) one has inbuilt UART other doesn’t have that
c) one needs some additional circuitry to operate while the other doesn’t have that
d) one is used just for transmission while the other is used for both transmission as well as reception
View Answer
Explanation: MAX232 needs some extra capacitors at pins like 1,2 and 3,4 while on the other hand MAX233 has that inbuilt capacitors built inside it only.
4. Which of the following is correct about the baud rate during serial transmission?
a) it tells us about the speed at which the transmission is going to place
b) it tells us about the number of bits transferred during a second
c) none of the mentioned
d) all of the mentioned
View Answer
Explanation: Baud Rate tells us about the speed in which the transmission is being done and this speed is measured in terms of bits per second.
5. With fosc=8 MHz, what will the count that has to filled in the UBRR register to account for the 9600 baud rate?
a) 67H
b) CEH
c) 33H
d) 34H
View Answer
Explanation: The count that had to be filled in the UBRR register is calculated as (fosc/16(desired baud rate))-1.
6. The USART in AVR based microcontrollers operate at which of the following modes?
a) double speed asynchronous mode
b) master synchronous
c) slave synchronous
d) all of the mentioned
View Answer
Explanation: The USART in AVR consists of the following modes. They are the normal asynchronous mode, double speed asynchronous mode, slave synchronous and the master synchronous mode.
7. Which bit of the UCSRA is used for doubling the baud rate of the transmission?
a) DOR
b) PE
c) U2X
d) MPCM
View Answer
Explanation: U2X bit of the UCSRA is used for doubling the baud rate of the transmission.
8. What is the use of the PE and the FE bits of the UCSRA register?
a) they are used for keeping a check at the speed of transmission and reception
b) they are used for keeping a check at the data bits to be transferred
c) they are used to keep the transmission error free
d) they are used as extra redundant bits with no use
View Answer
Explanation: PE and the FE bits of the UCSRA register are used for error checking in the transmission.
9. Which of the following bits are used for setting the data frame size?
a) UCSZ0
b) U2X
c) DOR
d) MPCM
View Answer
Explanation: UCSZ0 and UCSZ1 bits of the UCSRB register and the UCSZ2 bit of the UCSRC register are used for setting the data frame size in AVR based microcontrollers.
10. Which of the following parameters should the transmitter and the receiver agree upon before starting a serial transmission?
a) baud rate
b) frame size
c) stop bit
d) all of the mentioned
View Answer
Explanation: Before starting the serial transmission, the following parameters should be taken care of. They are the baud rate, frame size, stop bit and the parity bit.
Sanfoundry Global Education & Learning Series – Microcontroller.
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