UART vs USART: Difference Between UART and USART in Serial Communication

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Questions and Answers

What is the purpose of the JNB RI instruction in the serial communication process?

To start timer 1
To load the SCON register with the value 50H
To monitor the RI flag bit (correct)
To clear the RI flag bit

What is the effect of setting the SMOD bit in the PCON register?

It changes the serial mode to mode 0
It increases the baud rate of data transfer (correct)
It clears the RI flag bit
It decreases the baud rate of data transfer

What is the purpose of the RI flag bit in the serial communication process?

To indicate the start and stop bits of a character
To indicate the reception of an entire character (correct)
To indicate the end of a character transmission
To indicate the start of a character transmission

What is the difference between interrupts and polling in microcontrollers?

Interrupts occur when a device needs service, while polling occurs when a device is idle (A) Signup and view all the answers

What is the function of the SCON register in the serial communication process?

To select the serial communication mode (D) Signup and view all the answers

What is the purpose of the CLR RI instruction in the serial communication process?

To clear the RI flag bit (A) Signup and view all the answers

What is the purpose of the SCON register in 8051 microcontroller?

Control data transfer through TXd and RXd pins (C) Signup and view all the answers

Which register in the 8051 microcontroller is responsible for framing data with start and stop bits before transmission over the TxD line?

SBUF register (C) Signup and view all the answers

What happens when a byte data is written into the SBUF register in 8051 microcontroller?

The data is framed with start and stop bits for transmission (D) Signup and view all the answers

What is the function of the SBUF register in the 8051 microcontroller when data is received via the RxD line?

Store the data for further processing (A) Signup and view all the answers

In serial communication with the 8051 microcontroller, what task is done by the 8051 when data is received via the RxD line?

Deframe the data to construct a byte (B) Signup and view all the answers

What is the significance of the SCON register's settings concerning serial communication in the 8051 microcontroller?

Define the synchronization and data frame format (D) Signup and view all the answers

What is the purpose of start and stop bits in asynchronous serial data communication?

To indicate the beginning and end of a character (D) Signup and view all the answers

How many bits do start and stop bits consist of in asynchronous communication?

Start bit is 1 bit, stop bit can be 1 or 2 bits (B) Signup and view all the answers

What is the role of the start bit in serial communication?

Indicate the beginning of the character (B) Signup and view all the answers

In block-oriented data transfers, what method is generally used?

Synchronous method (B) Signup and view all the answers

What is the measure of data transfer rate in serial data communication?

Bits per second (bps) (D) Signup and view all the answers

What do baud rate and bps refer to in serial communication?

The rate of signal changes per second and bits per second, respectively (A) Signup and view all the answers

Study Notes

UART and USART

UART stands for Universal Asynchronous Receiver-Transmitter
USART stands for Universal Synchronous-Asynchronous Receiver-Transmitter

Asynchronous Serial Data Communication

Widely used for character-oriented transmissions
Each character is placed in between start and stop bits, known as framing
Start bit is always one bit, but the stop bit can be one or two bits
Start bit is always 0 (low) and the stop bit(s) is 1 (high)

Data Transfer Rate

Measured in bits per second (bps)
Baud rate is a modem terminology and is defined as the number of signal changes per second
In modems, a single change of signal can transfer several bits of data

Serial Communication in 8051 Microcontroller

SCON register is used to control data transfer through TXd and RXd pins
SCON register is loaded with the value 50H to indicate serial mode 1, where an 8-bit data is framed with start and stop bits
TR1 is set to 1 to start timer 1
RI flag bit is monitored to see if an entire character has been received
When RI is raised, SBUF has the byte, and its contents are moved to a safe place

Doubling Baud Rate

Two ways to increase the baud rate:
- Using a higher frequency crystal
- Changing a bit in the PCON register
PCON register is an 8-bit register
SMOD bit in PCON register can be set to high by software to double the baud rate

Interrupts

Interrupts: a device notifies the microcontroller by sending an interrupt signal, and the microcontroller interrupts its current task to serve the device
Interrupt service routine (ISR) or interrupt handler is the program associated with the interrupt
Polling: the microcontroller continuously monitors the status of a given device

8051 Serial Port

Synchronous and Asynchronous serial communication modes
Four modes of operation: Mode 0, Mode 1, Mode 2, and Mode 3
SCON register is used to control data transfer through TXd and RXd pins

SBUF register: an 8-bit communication register used solely for serial communication
SCON register: used to control data transfer through TXd and RXd pins
PCON register: an 8-bit register used to control the baud rate

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Description

Learn about the differences between UART (universal asynchronous Receiver transmitter) and USART (universal synchronous-asynchronous Receivertransmitter) in the context of asynchronous serial data communication. Explore concepts such as start and stop bits, framing, and block-oriented data transfers.

UART vs USART in Asynchronous Serial Communication

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