ATMEGA640 datasheet(210/436 Pages) MICROCHIP

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ATmega640/V-1280/V-1281/V-2560/V-2561/V [DATASHEET]

DS40002211A

Note:

1. See “About Code Examples” 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.

22.7.2

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

lds

r17, UCSRnA

sbrs

r17, RXCn

rjmp

USART_Receive

; Get and return received data from buffer

lds

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;

}

ATMEGA640 Datasheet(PDF) 210 Page - Microchip Technology