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Usart: Universal Synchronous Asynchronous Receiver Transmitter

The document discusses the Universal Synchronous Asynchronous Receiver Transmitter (USART) communication protocol. It describes the USART packet format which includes a start bit, 8 data bits, an optional parity bit, and a stop bit. It discusses asynchronous and synchronous transmission modes and typical baud rates. It also outlines the USART registers used to control data transmission and reception, set baud rates, interrupt handling, and more. The PD0 and PD1 pins on the Arduino board are used for the receiver and transmitter, respectively.

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212 views15 pages

Usart: Universal Synchronous Asynchronous Receiver Transmitter

The document discusses the Universal Synchronous Asynchronous Receiver Transmitter (USART) communication protocol. It describes the USART packet format which includes a start bit, 8 data bits, an optional parity bit, and a stop bit. It discusses asynchronous and synchronous transmission modes and typical baud rates. It also outlines the USART registers used to control data transmission and reception, set baud rates, interrupt handling, and more. The PD0 and PD1 pins on the Arduino board are used for the receiver and transmitter, respectively.

Uploaded by

hola
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PPSX, PDF, TXT or read online on Scribd
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USART

Universal Synchronous Asynchronous Receiver Transmitter

It is a Communication Protocol for Serial Data Transmission


developed by the EIA…
Data is sent in the form of PACKETS or FRAMES which is compose of
data bits and control bits..

DATA FIELD DATA FIELD STOP BIT PARITY BIT


USART packet format: 1 start bit, 8 data bits, 1 parity bit, 1 stop bit.

Data Bits : 5-8 bits


Stop Bit: 0 or 1 or 2
Parity Bit : Optional (Even or Odd)
BAUD RATE : The number of Symbols transmitted per second
Typical Values are 1200, 2400, 9600, 19200 etc..

Mode Of Transmission :

Asynchronous - Transfers a single byte at a time.

Synchronous- Transfers a block of data (characters) at a


time.
RxD
TxD

In Robomart Arduino Board


PD0 is Receiver (RxD) Pin 2
PD1 is Transmitter (TxD) Pin 3

USART Needs To Be Enabled By The User Through Software..


Serial Port
It is a set of 9 PINS used for serial data communication
between two µCs or between µC and a Computer…
THIS IS
SERIAL PORT
RS-232
The RS-232 standard defines the voltage levels that
correspond to logical one and logical zero levels in serial
communication..

Valid signals are plus or minus 3 to 15 volts. The range


near zero volts is not a valid RS-232 level..

Logic one is defined as a negative voltage and logic zero is


positive..
Voltage Levels in Our Microcontroller are
Logic High= 5Volt
Logic Low= 0 Volt
How Can a microcontroller communicate by using RS-232
Standard ??

Solution is MAX 232 IC


MAX 232 Connection
USART I/O DATA REGISTER

This Register stores the data to be transmitted or data


being Received…

UDRE bit in UCSRA Register should be set and transmitter


to be enabled for Data Transmission…
UCSRA-USART Control and Status Register A

RXC bit is set when data is available in the receive


buffer and cleared when the receive buffer is empty..

TXC bit is set when data transmission is complete…

UDRE bit is set when transmit buffer (UDR) is ready


to receive new data…
UCSRB-USART Control and Status Register B

RXCIE: Receive Complete interrupt will be generated if RXCIE bit is set.


TXCIE: Transmit Complete interrupt will be generated if TXCIE bit is set.
UDRIE: Data Register Empty interrupt will be generated if UDRIE bit is set.
RXEN: To enable the USART receiver ..
TXEN: To enable the USART transmitter..
UCsZ2: To set the character size in combination with bit UCZ1 and UCZ0..
UCSRC-USART Control and Status Register C

URSEL: This bit must be one to write the UCSRC...


UMSEL: To select between Asynchronous and Synchronous
mode..
UPM1 & UPM0: To Select Parity Bit..
USBS : To Select Stop Bit..
UCZ1 & UCZ0: To Select Character Size..
UCPOL: To Select Clock Polarity..
UBRRL &UBRRH-USART Baud Rate Register

This Register Stores The Value of Baud rate .


To write in the UBRRH , URSEL bit must be zero.
THANK YOU

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