116
2467S–AVR–07/09
ATmega128
The following code examples show how to do an atomic read of the TCNTn Register contents.
Reading 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 returns the TCNTn value in the r17:r16 register pair.
Assembly Code Example
TIM16_ReadTCNTn:
; Save global interrupt flag
in
r18,SREG
; Disable interrupts
cli
; Read TCNTn into r17:r16
in
r16,TCNTnL
in
r17,TCNTnH
; Restore global interrupt flag
out
SREG,r18
ret
C Code Example
unsigned
int
TIM16_ReadTCNTn( void )
{
unsigned
char
sreg;
unsigned
int
i;
/* Save global interrupt flag */
sreg = SREG;
/* Disable interrupts */
__disable_interrupt();
/* Read TCNTn into i */
i = TCNTn;
/* Restore global interrupt flag */
SREG = sreg;
return
i;
}
