Rainbow-electronics ATmega8515L Uživatelský manuál stáhnout pdf (Strana 99)

ATmega8515(L)

2512A–AVR–04/02

The following codeexamplesshowhow to doanatomicwrite of theTCNT1 Register

contents. Writing any of the OCR1A/B orICR1 Registers can be done by using the

same principle.

Note: 1. Theexample codeassumes that the part specificheaderfileis included.

Theassembly codeexample requires that the r17:r16registerpaircontains thevalue to

be written to TCNT1.

Reusing the Temporary High

Byte Register

If writing to morethan one 16-bit registerwherethe highbyte is the same for all registers

written, then the highbyte only needs to be written once. However, note that the same

ruleof atomic operation describedpreviously alsoapplies in thiscase.

Assembly Code Example

(1)

TIM16_WriteTCNT1:

;

Save global interrupt flag

in r18,SREG

;

Disable interrupts

cli

;

Set TCNT

r17:r16

out TCNT

1H,r17

out TCNT

1L,r16

;

Restore global interrupt flag

out SREG,r18

ret

CCode Example

(1)

void TIM16_WriteTCNT1( unsigned int i )

{

unsigned char sreg;

unsigned int i;

Save global interrupt flag

sreg = SREG;

Disable interrupts

_CLI();

Set TCNT

to i

TCNT

1 =i;

Restore global interrupt flag

SREG = sreg;

}

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