ATmega328P datasheet(183/448 Pages) ATMEL

183 / 448 page

183

8161D–AVR–10/09

ATmega48PA/88PA/168PA/328P

Note:

1. See ”About Code Examples” on page 7.

More advanced initialization routines can be made that include frame format as parameters, dis-

able interrupts and so on. However, many applications use a fixed setting of the baud and

control registers, and for these types of applications the initialization code can be placed directly

in the main routine, or be combined with initialization code for other I/O modules.

19.6

Data Transmission – The USART Transmitter

The USART Transmitter is enabled by setting the Transmit Enable (TXEN) bit in the UCSRnB

den by the USART and given the function as the Transmitter’s serial output. The baud rate,

mode of operation and frame format must be set up once before doing any transmissions. If syn-

Assembly Code Example(1)

USART_Init:

; Set baud rate

out

UBRRnH, r17

out

UBRRnL, r16

; Enable receiver and transmitter

ldi

r16, (1<<RXENn)|(1<<TXENn)

out

UCSRnB,r16

; Set frame format: 8data, 2stop bit

ldi

r16, (1<<USBSn)|(3<<UCSZn0)

out

UCSRnC,r16

ret

C Code Example

(1)

#define FOSC 1843200 // Clock Speed

#define BAUD 9600

#define MYUBRR FOSC/16/BAUD-1

void

main( void )

{

...

USART_Init(MYUBRR)

...

}

void

USART_Init( unsigned int ubrr)

{

/*Set baud rate */

UBRR0H = (unsigned char)(ubrr>>8);

UBRR0L = (unsigned char)ubrr;

Enable receiver and transmitter */

UCSR0B = (1<<RXEN0)|(1<<TXEN0);

/* Set frame format: 8data, 2stop bit */

UCSR0C = (1<<USBS0)|(3<<UCSZ00);

}

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