ATMEGA649 Datasheet, PDF(109/375 Page) ATMEL Corporation – 8-bit Microcontroller with In-System Programmable Flash

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ATMEGA649 Datasheet, PDF (109/375 Pages) ATMEL Corporation – 8-bit Microcontroller with In-System Programmable Flash

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ATmega329/3290/649/6490

The following code examples show how to do an atomic read of the TCNT1 Register

contents. Reading any of the OCR1A/B or ICR1 Registers can be done by using the

same principle.

Assembly Code Example(1)

TIM16_ReadTCNT1:

; Save global interrupt flag

in r18,SREG

; Disable interrupts

cli

; Read TCNT1 into r17:r16

in r16,TCNT1L

in r17,TCNT1H

; Restore global interrupt flag

out SREG,r18

ret

C Code Example(1)

unsigned int TIM16_ReadTCNT1( void )

{

unsigned char sreg;

unsigned int i;

/* Save global interrupt flag */

sreg = SREG;

/* Disable interrupts */

__disable_interrupt();

/* Read TCNT1 into i */

i = TCNT1;

/* Restore global interrupt flag */

SREG = sreg;

return i;

}

Note: 1. See âAbout Code Examplesâ on page 8.

The assembly code example returns the TCNT1 value in the r17:r16 register pair.

2552HâAVRâ11/06

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