Datasheet

143
ATmega32A [DATASHEET]
Atmel-8155D-AVR-ATmega32A-Datasheet_02/2014
The USART has to be initialized before the function can be used. For the assembly code, the data to be sent is
assumed to be stored in Register R16.
Note: 1. See “About Code Examples” on page 6.
The function simply waits for the transmit buffer to be empty by checking the UDRE Flag, before loading it with new
data to be transmitted. If the Data Register Empty Interrupt is utilized, the interrupt routine writes the data into the
buffer.
20.6.2 Sending Frames with 9 Data Bit
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 charac-
ters. For the assembly code, the data to be sent is assumed to be stored in Registers R17:R16.
Assembly Code Example
(1)
USART_Transmit:
; Wait for empty transmit buffer
sbis UCSRA,UDRE
rjmp USART_Transmit
; Put data (r16) into buffer, sends the data
out UDR,r16
ret
C Code Example
(1)
void USART_Transmit( unsigned char data )
{
/* Wait for empty transmit buffer */
while ( !( UCSRA & (1<<UDRE)) )
;
/* Put data into buffer, sends the data */
UDR = data;
}