In this article, I have tried to collect UART Interview questions that can be asked by your Interviewer. A UART is a chip for asynchronous serial communication. It takes bytes of data and transmits the individual bits in a sequential fashion with the help of a shift register. The shift register is the fundamental method of conversion between serial and parallel forms.
Interview Questions On UART:
So, let’s see the list of UART Interview Questions.
Q) What is the Full Form of UART?
UART stands for Universal Asynchronous Receiver Transmitter.
Q) What is UART?
A UART is a chip for asynchronous serial communication in which the data format and transmission speeds are configurable. It sends data bits one by one, from the least significant (Lsb) to the most significant (Msb), framed by start and stop bits.
Q) What is the communication mode of UART?
Communication may be 3 modes:
- Simplex (Transmit in one direction only).
- Half duplex ( Either transmit or receuwv)
- Full duplex (both devices send and receive at the same time).
Q) What is the byte order in UART?
LSB to MSB
Q) How many wires are used in UART Communication?
Two wires are used in communication.
1. Transmitter (Tx)
2. Receiver (Rx)
Q) What is the essential element of the UART Frame?
The following are the essential elements of the UART Frame.
1. Start Bit.
2. Data Bit.
3. Parity Bit.
4. Stop Bit.
Q) What is the method of Transmission in UART?
Asynchronous.
Q) Maximum Number of Masters in UART?
One
Q) Maximum Number of Slaves in UART?
One.
Q) Does the UART interface use a clock signal to synchronize the transmitter and receiver devices?
No
Explanation: Instead of a shared clock signal, the transmitter generates a bitstream based on its clock signal while the receiver uses its internal clock signal to sample the incoming data.
Q) What decides the rate of data transmission in UART?
The baud rate decides the rate of data transmission in UART.
Q) Could UART support for synchronous communication?
No.
USART supports asynchronous or synchronous both.
Q) How do the UART transmitter and receiver synchronize the data transmission and reception?
In communication, the data synchronizes with the help of the start and stop bits. The start bit is always low, while the stop bit is always high. The receiver detects the start bit and then samples the incoming data at the correct time to read the data bits
Q) What happens if the baud rate of the transmitter and receiver is different?
If the transmitter and receiver are configured with different baud rates, the actual result will be not expected. The reason is that the rate at which the transmitter alternates its TX pin and the rate at which the receiver samples its RX pin will be different. So it causes the receiver to miss the bits or read the same bit more than once.
Q) What are the advantages of UART?
- It only requires two wires for full-duplex communication.
- No required clock signal.
- It has a parity bit to check errors.
Q) What are the disadvantages of UART?
- The size of the data in the frame is limited.
- It does not support the multi-master and slave.
- Overhead in communication due to start and stop bits.
- You have to select the appropriate baud rate for the transmitter and receiver.
Q) What is the difference between UART, SPI, and I2C?
UART supports asynchronous communication so it works on the Baud rate beside the clock rate. Also unlike communication protocols like SPI and I2C, UART is a physical circuit. UART does not use the master/slave paradigm to control devices like I2C and SPI.
Q) How does flow control work in UART, and what are the different types of flow control?
The UART can halt the flow of data using flow control to prevent input buffers from overflowing. That means flow control is used to regulate the flow of data between the transmitter and receiver in UART communication.
UART supports two types of flow control: hardware flow control and software flow control.
For hardware flow control, the UART module utilizes the RTS/CTS flow control scheme commonly found in RS-232 networks.
For software flow control, the UART uses the XON/XOFF method. In this method, special characters are sent by the receiver to the transmitter that are used to suspend and resume transactions. This flow control method does not require additional hardware lines, which significantly reduces wiring complexity.
Q) What is the Loop Back Test in UART?
The loop-back test is a simple way to verify whether your UART is working in the proper way or not.
In the loop-back test, you just need to connect the RX to the Tx pin. If your communication setup is well then what you will transfer to the Tx will receive on the Rx.
Q) Explain the purpose of the UART parity bit, and how it helps detect errors.
A parity bit is an optional bit which used for error detection. When the entire data word has been sent, the transmitter may add a Parity Bit (both sender and receiver must agree on whether a Parity Bit is to be used).
When the receiver has received all of the bits in the data word, it may check for the Parity Bits, and then the receiver looks for a Stop Bit. If the Stop Bit does not appear when it is supposed to, the UART considers the entire word to be garbled and will report a Framing Error to the host processor when the data word is read.
Q) What are special transceiver conditions in uart?
- Overrun error.
- Underrun error.
- Framing error.
- Parity error.
- Break condition.
