Rainbow-electronics ATtiny861_V Manual do Utilizador descarregar pdf (Página 112)

112

2588B–AVR–11/06

ATtiny261/461/861

The following code examples show how to do an atomic write of the TCNT1 register contents.

Writing any of the OCR1A/B/C/D registers can be done by using the same principle.

Note: 1. The example code assumes that the part specific header file is included.

For I/O registers located in extended I/O map, “IN”, “OUT”, “SBIS”, “SBIC”, “CBI”, and “SBI”

instructions must be replaced with instructions that allow access to extended I/O. Typically

“LDS” and “STS” combined with “SBRS”, “SBRC”, “SBR”, and “CBR”.

The assembly code example requires that the r17:r16 register pair contains the value to be writ-

ten to TCNT1.

16.10.1 Reusing the temporary high byte register

If writing to more than one 10-bit register where the high byte is the same for all registers written,

then the high byte only needs to be written once. However, note that the same rule of atomic

operation described previously also applies in this case.

Assembly Code Example

TIM1_WriteTCNT1:

; Save global interrupt flag

in r18,SREG

; Disable interrupts

cli

; Set TCNT1 to r17:r16

out TC1H,r17

out TCNT1,r16

; Restore global interrupt flag

out SREG,r18

ret

C Code Example

void TIM1_WriteTCNT1( unsigned int i )

{

unsigned char sreg;

unsigned int i;

/* Save global interrupt flag */

sreg = SREG;

/* Disable interrupts */

_CLI();

/* Set TCNT1 to i */

TC1H = (i >> 8);

TCNT1 = (unsigned char)i;

/* Restore global interrupt flag */

SREG = sreg;

}

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