ATmega32A datasheet(158/352 Pages) ATMEL

158 / 352 page

158

8155B–AVR–07/09

ATmega32A

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.

Note:

1. See “About Code Examples” on page 6.

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.

19.7.2

Receiving Frames with 9 Databits

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.

The following code example shows a simple USART receive function that handles both 9-bit

characters and the status bits.

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

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;

}

ATmega32A Datasheet(PDF) 158 Page - ATMEL Corporation