ATtiny261-ESSZ datasheet(84/227 Pages) ATMEL

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7753C–AVR–07/09

ATtiny261/ATtiny461/ATtiny861

The following code examples show how to do an atomic write of the TCNT0H/L register con-

tents. Writing any of the OCR0A/B 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 TCNT0H/L.

14.9.1

Reusing the temporary high byte register

If writing to more than one 16-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

TIM0_WriteTCNT

; Save global interrupt flag

r18,SREG

; Disable interrupts

cli

; Set TCNT

0 to r17:r16

out

TCNT

0H,r17

out

TCNT

0L,r16

; Restore global interrupt flag

out

SREG,r18

ret

C Code Example

void

TIM0_WriteTCNT0( unsigned int i )

{

unsigned char

sreg;

/* Save global interrupt flag */

sreg = SREG;

/* Disable interrupts */

_CLI();

/* Set TCNT0 to i */

TCNT0H = (i >> 8);

TCNT0L = (unsigned char)i;

/* Restore global interrupt flag */

SREG = sreg;

}

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