Datasheet

181
8021G–AVR–03/11
ATmega329P/3290P
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 9.
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.
19.7.2 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
in 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;
}