ATmega32U2 datasheet(158/314 Pages) ATMEL

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7799B–AVR–07/09

ATmega8U2/16U2/32U2

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 “Code Examples” on page 6.

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 (UCSZn=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.

The following code example shows a simple USART receive function that handles both nine bit

characters and the status bits.

Assembly Code Example

(1)

USART_Receive:

; Wait for data to be received

sbis UCSRnA, RXCn

rjmp USART_Receive

; Get and return received data from buffer

r16, UDRn

ret

C Code Example(1)

unsigned char USART_Receive( void )

{

/* Wait for data to be received */

while ( !(UCSRnA & (1<<RXCn)) )

;

/* Get and return received data from buffer */

return UDRn;

}

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