ATMEGA16-16AU SL602 Atmel, ATMEGA16-16AU SL602 Datasheet - Page 151

• Manufacturer Part Number: ATMEGA16-16AU SL602
• Manufacturer: Atmel

2466T–AVR–07/10
frame. The Shift Register is loaded with new data if it is in idle state (no ongoing transmission) or
immediately after the last stop bit of the previous frame is transmitted. When the Shift Register is
loaded with new data, it will transfer one complete frame at the rate given by the Baud Register,
U2X bit or by XCK depending on mode of operation.
The following code examples show a simple USART transmit function based on polling of the
Data Register Empty (UDRE) Flag. When using frames with less than eight bits, the most signif-
icant bits written to the UDR are ignored. 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:
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.
Assembly Code Example
C Code Example
USART_Transmit:
void USART_Transmit( unsigned char data )
{
}
; Wait for empty transmit buffer
sbis UCSRA,UDRE
rjmp USART_Transmit
; Put data (r16) into buffer, sends the data
out
ret
/* Wait for empty transmit buffer */
while ( !( UCSRA & (1<<UDRE)) )
/* Put data into buffer, sends the data */
UDR = data;
1. See “About Code Examples” on page 7.
UDR,r16
;
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(1)
ATmega16(L)
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