Datasheet

115
7728G–AVR–06/10
ATtiny87/ATtiny167
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.
Note: 1. The example code assumes that the part specific header file is included.
The assembly code example requires that the r17:r16 register pair contains the value to be
written to TCNT1.
12.3.2 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 writ-
ten, 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.
12.4 Timer/Counter Clock Sources
The Timer/Counter can be clocked by an internal or an external clock source. The clock
source is selected by the Clock Select logic which is controlled by the Clock Select (CS12:0)
bits located in the Timer/Counter control Register B (TCCR1B). For details on clock sources
and prescaler, see “Timer/Counter1 Prescaler” on page 107.
Assembly Code Example
(1)
TIM16_WriteTCNT1:
; Save global interrupt flag
in r18,SREG
; Disable interrupts
cli
; Set TCNT1 to r17:r16
sts TCNT1H,r17
sts TCNT1L,r16
; Restore global interrupt flag
out SREG,r18
ret
C Code Example
(1)
void TIM16_WriteTCNT1(unsigned int i)
{
unsigned char sreg;
unsigned int i;
/* Save global interrupt flag */
sreg = SREG;
/* Disable interrupts */
_CLI();
/* Set TCNT1 to i */
TCNT1 = i;
/* Restore global interrupt flag */
SREG = sreg;
}