atmega32c1 ATMEL Corporation, atmega32c1 Datasheet - Page 111

• Manufacturer Part Number: atmega32c1
• Description: Atmega32m1 Automotive 8-bit Avr Microcontroller With 32k/64k Bytes In-system Programmable Flash
• Manufacturer: ATMEL Corporation

13.2.1
13.3
7647A–AVR–02/08
Timer/Counter Clock Sources
Reusing the Temporary High Byte Register
The following code examples show how to do an atomic write of the TCNTn Register contents.
Writing any of the OCRnx or ICRn Registers can be done by using the same principle.
Note:
The assembly code example requires that the r17:r16 register pair contains the value to be writ-
ten to TCNTn.
If writing to more than one 16-bit register where the high byte is the same for all registers 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.
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 (CSn2:0) bits
located in the Timer/Counter control Register B (TCCRnB). For details on clock sources and
prescaler, see
Assembly Code Example
C Code Example
TIM16_WriteTCNTn:
void TIM16_WriteTCNTn( unsigned int i )
{
}
; Save global interrupt flag
in r18,SREG
; Disable interrupts
cli
; Set TCNTn to r17:r16
out TCNTnH,r17
out TCNTnL,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 TCNTn to i */
TCNTn = i;
/* Restore global interrupt flag */
SREG = sreg;
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”.
“Timer/Counter0 and Timer/Counter1 Prescalers” on page
(1)
(1)
ATmega32/64/M1/C1
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