This set of 8051 Micro-controller Multiple Choice Questions & Answers (MCQs) focuses on ” Serial Port Communication”.
1. Which devices are specifically being used for converting serial to parallel and from parallel to serial respectively?
d) serial communication
Explanation: Some registers like the parallel in serial out and serial in parallel out are used to convert serial data into parallel and vice versa respectively.
2. 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
Explanation: UART stands for Universal Asynchronous receiver-transmitter and USART stands for Universal Synchronous and Asynchronous receiver-transmitter.
3. 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
Explanation: In data framing in asynchronous means of communication, the data is packed between the start and the stop bit. This is done so as to tell the other computer about the start and the end of the data.
4. Which of the following signal control the flow of data?
c) RTS & DTR
d) None of the mentioned
Explanation: RTS is a request to send control signal which is a control for the flow of data. On the other hand DTR is a Data Terminal Ready control signal which tells about the current status of the DTE.
5. 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
Explanation: TTL logic or the transistor logic level is the logic that is understood by the micro-controllers/microprocessors.
6. 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
Explanation: In null modem connection the RxD of one is the TxD for the other.
7. 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
Explanation: To make two devices compatible with each other baud rate is mentioned in the serial communication so that the transmission becomes easy and error free.
8. With what frequency UART operates( where f denoted the crystal frequency )?
Explanation: UART frequency is the crystal frequency f/12 divided by 32, that comes out to be f/384.
9. 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
Explanation: SCON register is mainly used for programming the start bits, stop bits and data bits of framing. As it consists of bits like RB8, TB8, SM0, SM1, SM2 etc.
10. 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
Explanation: PCON register consists of SMOD bit as its D7 bit, so if we set this bit then the baud rate gets doubled.
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