Atmel ATmega328P Xplained Mini MEGA328P-XMINI MEGA328P-XMINI Ficha De Dados

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ATmega48A/PA/88A/PA/168A/PA/328/P [DATASHEET]

Atmel-8271H-AVR- ATmega-Datasheet_08/2014

Note:

1.

For I/O Registers located in extended I/O map, “IN”, “OUT”, “SBIS”, “SBIC”, “CBI”, and “SBI” instructions must 
be replaced with instructions that allow access to extended I/O. Typically “LDS” and “STS” combined with 
“SBRS”, “SBRC”, “SBR”, and “CBR”.

The receive function example reads all the I/O Registers into the Register File before any computation is done. 
This gives an optimal receive buffer utilization since the buffer location read will be free to accept new data as 
early as possible.

The USART Receiver has one flag that indicates the Receiver state.

The Receive Complete (RXCn) Flag indicates if there are unread data present in the receive buffer. This flag is 
one when unread data exist in the receive buffer, and zero when the receive buffer is empty (i.e., does not 

Assembly Code Example

USART_Receive:

; Wait for data to be received

in r16, UCSRnA

sbrs r16, RXCn

USART_Receive

; Get status and 9th bit, then data from buffer

r18, UCSRnA

r17, UCSRnB

r16, UDRn

; If error, return -1

r18,(1<<FEn)|(1<<DORn)|(1<<UPEn)

USART_ReceiveNoError

r17, HIGH(-1)

r16, LOW(-1)

USART_ReceiveNoError:

; Filter the 9th bit, then return

r17

r17, 0x01

C Code Example

unsigned int USART_Receive( void )

{

unsigned char status, resh, resl;

/* Wait for data to be received */

while ( !(UCSRnA & (1<<RXCn)) )

;

/* Get status and 9th bit, then data */

/* from buffer */

status = UCSRnA;

resh = UCSRnB;

resl = UDRn;

/* If error, return -1 */

if ( status & (1<<FEn)|(1<<DORn)|(1<<UPEn) )

return -1;

/* Filter the 9th bit, then return */

resh = (resh >> 1) & 0x01;

return ((resh << 8) | resl);

}