ATmega16A datasheet(93/352 Pages) ATMEL

93 / 352 page

8154B–AVR–07/09

ATmega16A

Note:

1. See “About Code Examples” on page 7.

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

ten to TCNT1.

16.3.1

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.

16.4

Timer/Counter Clock Sources

The Timer/Counter can be clocked by an internal or an external clock source. The clock source

is selected by the Clock Select logic which is controlled by the Clock Select (CS12:0) bits

located in the Timer/Counter Control Register B (TCCR1B). For details on clock sources and

prescaler, see “Timer/Counter0 and Timer/Counter1 Prescalers” on page 86.

16.5

Counter Unit

The main part of the 16-bit Timer/Counter is the programmable 16-bit bi-directional counter unit.

Figure 16-2 shows a block diagram of the counter and its surroundings.

Assembly Code Example

(1)

TIM16_WriteTCNT1:

; Save global interrupt flag

r18,SREG

; Disable interrupts

cli

; Set TCNT1 to r17:r16

out

TCNT1H,r17

out

TCNT1L,r16

; Restore global interrupt flag

out

SREG,r18

ret

C Code Example

(1)

void

TIM16_WriteTCNT1 ( unsigned int i )

{

unsigned char

sreg;

unsigned int

/* Save global interrupt flag */

sreg = SREG;

/* Disable interrupts */

_CLI();

/* Set TCNT1 to i */

TCNT1 = i;

/* Restore global interrupt flag */

SREG = sreg;

}

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