Rainbow-electronics ATmega8HVD User Manual download pdf (Page 84)

8052B–AVR–09/08

ATmega4HVD/8HVD

The following code examples show how to do an atomic read of the TCNTn register contents.

Reading any of the OCRn register can be done by using the same principle.

Note: 1. See ”About Code Examples” on page 5.

The assembly code example returns the TCNTnH/L value in the r17:r16 register pair.

Assembly Code Example

TIMn_ReadTCNTn:

; 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

C Code Example

unsigned int TIMn_ReadTCNTn( void )

{

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;

}

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Rainbow-electronics ATmega8HVD User Manual Page 84