atmega323l ATMEL Corporation, atmega323l Datasheet - Page 92

• Manufacturer Part Number: atmega323l
• Description: Atmega323 8-bit Avr Microcontroller With 32k Bytes Of In-system Programmable Flash
• Manufacturer: ATMEL Corporation

Accessing
UBRRH/UCSRC
Registers
Write Access
92
ATmega323(L)
The UBRRH Register shares the same I/O location as the UCSRC Register. Therefore
some special consideration must be taken when accessing this I/O location.
When doing a write access of this I/O location, the high bit of the value written, the
USART Register Select (URSEL) bit, controls which one of the two registers that will be
written. If URSEL is zero during a write operation, the UBRRH value will be updated. If
URSEL is one, the UCSRC setting will be updated.
The following code examples show how to access the two registers.
Note:
As the code examples illustrate, write accesses of the two registers are relatively unaf-
fected of the sharing of I/O location.
Assembly Code Examples
C Code Examples
...
; Set UBRRH to 2
ldi r16,0x02
out UBRRH,r16
...
; Set the USBS and the UCSZ1 bit to one, and
; the remaining bits to zero.
ldi r16,(1<<URSEL)|(1<<USBS)|(1<<UCSZ1)
out UCSRC,r16
...
...
/* 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)
...
1. The example code assumes that the part specific header file is included.
(1)
(1)
1457G–AVR–09/03