Rainbow Electronics ATtiny861_V User Manual
Page 82
82
2588B–AVR–11/06
ATtiny261/461/861
The following code examples show how to do an atomic read of the TCNT0 register contents.
Reading any of the OCR0 register 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 returns the TCNT0H/L value in the r17:r16 register pair.
Assembly Code Example
TIM0_ReadTCNT
0:
; Save global interrupt flag
in
r18,SREG
; Disable interrupts
cli
; Read TCNT
0 into r17:r16
in
r16,TCNT
0L
in
r17,TCNT
0H
; Restore global interrupt flag
out
SREG,r18
ret
C Code Example
unsigned int
TIM0_ReadTCNT0( void )
{
unsigned char sreg;
unsigned int i;
/* Save global interrupt flag */
sreg = SREG;
/* Disable interrupts */
_CLI();
/* Read TCNT0 into i */
i = TCNT0L;
i |= ((unsigned int)TCNT0H << 8);
/* Restore global interrupt flag */
SREG = sreg;
return i;
}