ATMEGA644PV ATMEL [ATMEL Corporation], ATMEGA644PV Datasheet - Page 114

• Manufacturer Part Number: ATMEGA644PV
• Description: 8-bit Microcontroller with 16/32/64K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

114
ATmega164P/324P/644P
The following code examples show how to do an atomic read of the TCNTn Register contents.
Reading any of the OCRnA/B/C or ICRn Registers can be done by using the same principle.
Note:
The assembly code example returns the TCNTn value in the r17:r16 register pair.
Assembly Code Example
C Code Example
TIM16_ReadTCNTn:
unsigned int TIM16_ReadTCNTn( void )
{
}
; Save global interrupt flag
in r18,SREG
; Disable interrupts
cli
; Read TCNTn into r17:r16
in r16,TCNTnL
in r17,TCNTnH
; Restore global interrupt flag
out SREG,r18
ret
unsigned char sreg;
unsigned int i;
/* Save global interrupt flag */
sreg = SREG;
/* Disable interrupts */
_CLI();
/* Read TCNTn into i */
i = TCNTn;
/* Restore global interrupt flag */
SREG = sreg;
return i;
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”.
(1)
(1)
8011D–AVR–02/07