Multiple Choice Questions & Answers on 8051 Microcontroller  Serial Port Communication

1. With what frequency UART operates( where f denoted the crystal frequency )?

a) f/12

b) f/32

c) f/144

d) f/384

Answer: f/384

2. What is a null modem connection?

a) no data transmission

b) no MAX232

c) the RxD of one is the TxD for the other

d) no serial communication

Answer: the RxD of one is the TxD for the other

3. What should be done if we want to double the baud rate?

a) change a bit of the TMOD register

b) change a bit of the PCON register

c) change a bit of the SCON register

d) change a bit of the SBUF register

Answer: change a bit of the PCON register

4. Which of the following signal control the flow of data?

a) RTS

b) DTR

c) RTS & DTR

d) None of the mentioned

Answer: RTS

5. Which of the following best describes the use of framing in asynchronous means of communication?

a) it binds the data properly

b) it tells us about the start and stops of the data to be transmitted or received

c) it is used for error checking

d) it is used for flow control

Answer: it tells us about the start and stops of the data to be transmitted or received

6. Which of the following best states the reason that why baud rate is mentioned in serial communication?

a) to know about the no of bits being transmitted per second

b) to make the two devices compatible with each other, so that the transmission becomes easy and error free

c) to use Timer 1

d) for wasting memory

Answer: to make the two devices compatible with each other, so that the transmission becomes easy and error free

7. Which devices are specifically being used for converting serial to parallel and from parallel to serial respectively?

a) timers

b) counters

c) registers

d) serial communication

Answer: registers

8. What is the function of the SCON register?

a) to control SBUF and SMOD registers

b) to program the start bit, stop bit, and data bits of framing

c) to control SMOD registers

d) none of the mentioned

Answer: to program the start bit, stop bit, and data bits of framing

9. What is the difference between UART and USART communication?

a) they are the names of the same particular thing, just the difference of A and S is there in it

b) one uses asynchronous means of communication and the other uses synchronous means of communication

c) one uses asynchronous means of communication and the other uses asynchronous and synchronous means of communication

d) one uses angular means of the communication and the other uses linear means of communication

Answer: one uses asynchronous means of communication and the other uses asynchronous and synchronous means of communication

10. Which of the following is the logic level understood by the micro-controller/micro-processor?

a) TTL logic level

b) RS232 logic level

c) None of the mentioned

d) TTL & RS232 logic level

Answer: TTL logic level