ATmega8(L)
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.
Assembly Code Example(1)
TIM16_WriteTCNT1:
; Save Global Interrupt Flag
in r18,SREG
; Disable interrupts
cli
; Set TCNT1 to r17:r16
outTCNT1H,r17
outTCNT1L,r16
; Restore Global Interrupt Flag
outSREG,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;
}
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.
Reusing the Temporary High
Byte Register
If writing to more than one 16-bit register where the High byte is the same for all regis-
ters written, 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.
79
2486M–AVR–12/03
ATMEL [ ATMEL ]
