ATmega644PA datasheet(117/468 Pages) ATMEL

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117

8152G–AVR–11/09

ATmega164PA/324PA/644PA/1284P

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:

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”.

The assembly code example returns the TCNTn value in the r17:r16 register pair.

Assembly Code Example

(1)

TIM16_ReadTCNT

; Save global interrupt flag

r18,SREG

; Disable interrupts

cli

; Read TCNT

n into r17:r16

r16,TCNT

r17,TCNT

; Restore global interrupt flag

out

SREG,r18

ret

C Code Example

(1)

unsigned int

TIM16_ReadTCNT

n( void )

{

unsigned char

sreg;

unsigned int

/* Save global interrupt flag */

sreg = SREG;

/* Disable interrupts */

_CLI();

/* Read TCNT

n into i */

i = TCNT

/* Restore global interrupt flag */

SREG = sreg;

return

}

ATmega644PA Datasheet(PDF) 117 Page - ATMEL Corporation

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