ATMEGA640 datasheet(142/449 Pages) ATMEL

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142

ATmega640/1280/1281/2560/2561

2549K–AVR–01/07

The following code examples show how to do an atomic write of the TCNTn Register

contents. Writing any of the OCRnA/B/C or ICRn Registers can be done by using the

same principle.

Note:

1. See “About Code Examples” on page 9.

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

be written to TCNTn.

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(1)

TIM16_WriteTCNTn:

; Save global interrupt flag

r18,SREG

; Disable interrupts

cli

; Set TCNTn to r17:r16

out

TCNTnH,r17

out

TCNTnL,r16

; Restore global interrupt flag

out

SREG,r18

ret

C Code Example

(1)

void

TIM16_WriteTCNTn( unsigned int i )

{

unsigned char

sreg;

unsigned int

/* Save global interrupt flag */

sreg = SREG;

/* Disable interrupts */

__disable_interrupt();

/* Set TCNTn to i */

TCNTn = i;

/* Restore global interrupt flag */

SREG = sreg;

}

ATMEGA640 Datasheet(PDF) 142 Page - ATMEL Corporation

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