ATmega88PA Automotive Atmel Corporation, ATmega88PA Automotive Datasheet - Page 116

• Manufacturer Part Number: ATmega88PA Automotive
• Manufacturer: Atmel Corporation

16.3.1
16.4
116
Timer/Counter Clock Sources
Atmel ATmega48PA/88PA/168PA [Preliminary]
Reusing the Temporary High Byte Register
The assembly code example requires that the r17:r16 register pair contains the value to be
written to TCNT1.
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.
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
Assembly Code Example
C Code Example
Note:
TIM16_WriteTCNT1:
void TIM16_WriteTCNT1( unsigned int i )
{
}
; Save global interrupt flag
in r18,SREG
; Disable interrupts
cli
; Set TCNT1 to r17:r16
out TCNT1H,r17
out TCNT1L,r16
; Restore global interrupt flag
out SREG,r18
ret
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;
1.
See ”About Code Examples” on page 7.
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”.
(1)
“Timer/Counter0 and Timer/Counter1 Prescalers” on page
(1)
140.
9223B–AVR–09/11