Datasheet

ldi r16,(1<<URSEL) | (1<<USBS) | (1<<UCSZ1)
out UCSRC,r16
:.
C Code Example
(1)
:.
/* Set UBRRH to 2 */
UBRRH = 0x02;
:.
/* Set the USBS and the UCSZ1 bit to one, and */
/* the remaining bits to zero. */
UCSRC = (1<<URSEL) | (1<<USBS) | (1<<UCSZ1);
:.
Note: 1. See About Code Examples.
As the code examples illustrate, write accesses of the two registers are relatively
unaffected of the sharing of I/O location.
Related Links
About Code Examples on page 19
23.10.2. Read Access
Doing a read access to the UBRRH or the UCSRC Register is a more complex operation. However, in
most applications, it is rarely necessary to read any of these registers.
The read access is controlled by a timed sequence. Reading the I/O location once returns the UBRRH
Register contents. If the register location was read in previous system clock cycle, reading the register in
the current clock cycle will return the UCSRC contents. Note that the timed sequence for reading the
UCSRC is an atomic operation. Interrupts must therefore be controlled (e.g., by disabling interrupts
globally) during the read operation.
The following code example shows how to read the UCSRC Register contents.
Assembly Code Example
(1)
USART_ReadUCSRC:
; Read UCSRC
in r16,UBRRH
in r16,UCSRC
ret
C Code Example
(1)
unsigned char USART_ReadUCSRC( void )
{
unsigned char ucsrc;
/* Read UCSRC */
ucsrc = UBRRH;
ucsrc = UCSRC;
return ucsrc;
}
Note: 1. See About Code Examples.
The assembly code example returns the UCSRC value in r16.
Reading the UBRRH contents is not an atomic operation and therefore it can be read as
an ordinary register, as long as the previous instruction did not access the register
location.
Related Links
Atmel ATmega32A [DATASHEET]
Atmel-8155I-ATmega32A_Datasheet_Complete-08/2016
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