Rainbow-electronics ATmega8515L Manual de usuario descargar pdf (Pagina 149)

149

ATmega8515(L)

2512A–AVR–04/02

Accessing

UBRRH/UCSRC

Registers

The UBRRH Registershares the same I/Olocation as the UCSRC Register.Therefore

some specialconsideration must betaken when accessing thisI/Olocation.

Write Access When doing a write access of thisI/Olocation, the highbit of thevalue written, the

USART RegisterSelect (URSEL) bit,controls which one of thetwo registers that will be

written. If URSEL iszero during a write operation, the UBRRH value will beupdated. If

URSEL is one, the UCSRCsetting will beupdated.

The following codeexamplesshowhow to access thetwo registers.

Note: 1. Theexample codeassumes that the part specificheaderfileis included.

As the codeexamples illustrate,write accesses of thetwo registers are relatively unaf-

fected of the sharing ofI/Olocation.

Assembly Code Examples

(1)

...

;

Set UBRRH to 2

ldi r16,0x02

out UBRRH,r16

...

;

Set the USBS and the UCSZ1 bit to one, and

he remaining bits to zero.

ldi r16,(1<<URSEL)|(1<<USBS)|(1<<UCSZ1)

out UCSRC,r16

...

CCode Examples

(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);

...

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Rainbow-electronics ATmega8515L Manual de usuario Pagina 149