ATMEGA2561V ATMEL [ATMEL Corporation], ATMEGA2561V Datasheet - Page 217

• Manufacturer Part Number: ATMEGA2561V
• Description: 8-bit Microcontroller with 64K/128K/256K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

Sending Frames with 9 Data
Bit
2549K–AVR–01/07
If 9-bit characters are used (UCSZn = 7), the ninth bit must be written to the TXB8 bit in
UCSRnB before the low byte of the character is written to UDRn. The following code
examples show a transmit function that handles 9-bit characters. For the assembly
code, the data to be sent is assumed to be stored in registers R17:R16.
Notes:
The ninth bit can be used for indicating an address frame when using multi processor
communication mode or for other protocol handling as for example synchronization.
Assembly Code Example
C Code Example
USART_Transmit:
void USART_Transmit( unsigned int data )
{
}
; Wait for empty transmit buffer
sbis UCSRnA,UDREn
rjmp USART_Transmit
; Copy 9th bit from r17 to TXB8
cbi
sbrc r17,0
sbi
; Put LSB data (r16) into buffer, sends the data
out
ret
/* Wait for empty transmit buffer */
while ( !( UCSRnA & (1<<UDREn))) )
/* Copy 9th bit to TXB8 */
UCSRnB &= ~(1<<TXB8);
if ( data & 0x0100 )
/* Put data into buffer, sends the data */
UDRn = data;
1. These transmit functions are written to be general functions. They can be optimized if
2. See “About Code Examples” on page 9.
UCSRnB |= (1<<TXB8);
the contents of the UCSRnB is static. For example, only the TXB8 bit of the UCSRnB
Register is used after initialization.
UCSRnB,TXB8
UCSRnB,TXB8
UDRn,r16
;
(1)(2)
ATmega640/1280/1281/2560/2561
(1)(2)
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