ATMEGA8_14 Datasheet, PDF (139/331 Pages) ATMEL Corporation – High-performance, Low-power Atmel

ATmega8(L)
bits of the data read from the UDR will be masked to zero. The USART has to be initialized
before the function can be used.
Assembly Code Example⁽¹⁾
USART_Receive:
; Wait for data to be received
sbis UCSRA, RXC
rjmp USART_Receive
; Get and return received data from buffer
in r16, UDR
ret
C Code Example⁽¹⁾
unsigned char USART_Receive( void )
{
/* Wait for data to be received */
while ( !(UCSRA & (1<<RXC)) )
;
/* Get and return received data from buffer */
return UDR;
}
Note: 1. See “About Code Examples” on page 8
The function simply waits for data to be present in the receive buffer by checking the RXC Flag,
before reading the buffer and returning the value.
Receiving Frames with
9 Data Bits
If 9-bit characters are used (UCSZ=7) the ninth bit must be read from the RXB8 bit in UCSRB
before reading the low bits from the UDR. This rule applies to the FE, DOR and PE Status Flags
as well. Read status from UCSRA, then data from UDR. Reading the UDR I/O location will
change the state of the receive buffer FIFO and consequently the TXB8, FE, DOR, and PE bits,
which all are stored in the FIFO, will change.
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