ATmega325P datasheet(174/364 Pages) ATMEL

174 / 364 page

174

8023F–AVR–07/09

ATmega325P/3250P

bits of the data read from the UDRn will be masked to zero. The USART has to be initialized

before the function can be used.

Note:

1. See Section “5.” on page 10.

The function simply waits for data to be present in the receive buffer by checking the RXCn Flag,

before reading the buffer and returning the value.

18.7.2

Receiving Frames with 9 Data Bits

If 9-bit characters are used (UCSZ=7), the ninth bit must be read from the RXB8n bit in UCSRnB

before reading the low bits from the UDRn. This rule applies to the FEn, DORn and UPEn Status

Flags as well. Read status from UCSRnA, then data from UDRn. Reading the UDRn I/O location

will change the state of the receive buffer FIFO and consequently the TXB8n, FEn, DORn and

UPEn bits, which all are stored in the FIFO, will change.

Assembly Code Example

(1)

USART_Receive:

; Wait for data to be received

sbis

UCSR0A, RXC0

rjmp

USART_Receive

; Get and return received data from buffer

r16, UDR0

ret

C Code Example(1)

unsigned char

USART_Receive( void )

{

/* Wait for data to be received */

while

( !(UCSR0A & (1<<RXC0)) )

;

/* Get and return received data from buffer */

return

UDR0;

}

ATmega325P データシート(PDF) 174 Page - ATMEL Corporation

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