Rainbow-electronics ATmega8HVD Bedienungsanleitung PDF herunterladen (Seite 85)

8052B–AVR–09/08

ATmega4HVD/8HVD

The following code examples show how to do an atomic write of the TCNTnH/L register con-

tents. Writing any of the OCRnA/B registers can be done by using the same principle.

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

The assembly code example requires that the r17:r16 register pair contains the value to be

written to TCNTnH/L.

16.9.1 Reusing the temporary high byte register

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.

Assembly Code Example

TIMn_WriteTCNTn:

; 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

C Code Example

void TIMn_WriteTCNTn( unsigned int i )

{

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;

}

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Rainbow-electronics ATmega8HVD Bedienungsanleitung Seite 85