ATMEga64L ATMEL Corporation, ATMEga64L Datasheet - Page 177

• Manufacturer Part Number: ATMEga64L
• Description: 8-bit AVR Microcontroller with 64K Bytes In-System Programmable Flash
• Manufacturer: ATMEL Corporation

Sending Frames with 9 Data
Bits
2490G–AVR–03/04
If 9-bit characters are used (UCSZ = 7), the ninth bit must be written to the TXB8 bit in
UCSRB before the low byte of the character is written to UDR. 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.
Note:
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 UCSRA,UDRE
rjmp USART_Transmit
; Copy ninth 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 ( !( UCSRA & (1<<UDRE)) )
/* Copy ninth bit to TXB8 */
UCSRB &= ~(1<<TXB8);
if ( data & 0x0100 )
/* Put data into buffer, sends the data */
UDR = data;
1. These transmit functions are written to be general functions. They can be optimized if
UCSRB |= (1<<TXB8);
the contents of the UCSRB is static. For example, only the TXB8 bit of the UCSRB
Register is used after initialization.
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”.
UCSRB,TXB8
UCSRB,TXB8
UDR,r16
;
(1)
(1)
ATmega64(L)
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