
117
8161D–AVR–10/09
ATmega48PA/88PA/168PA/328P
Note:
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 returns the TCNT1 value in the r17:r16 register pair.
The following code examples show how to do an atomic write of the TCNT1 Register contents.
Writing any of the OCR1A/B or ICR1 Registers can be done by using the same principle.
TIM16_ReadTCNT
1:
; Save global interrupt flag
in
r18,SREG
; Disable interrupts
cli
; Read TCNT
1 into r17:r16
in
r16,TCNT
1L
in
r17,TCNT
1H
; Restore global interrupt flag
out
SREG,r18
ret
C Code Example
unsigned int
TIM16_ReadTCNT
1( void )
{
unsigned char
sreg;
unsigned int
i;
/* Save global interrupt flag */
sreg = SREG;
/* Disable interrupts */
_CLI();
/* Read TCNT
1 into i */
i = TCNT
1;
/* Restore global interrupt flag */
SREG = sreg;
return
i;
}