ATmega16 datasheet(88/315 Pages) ATMEL

88 / 315 page

ATmega16(L)

2466E–AVR–10/02

The following code examples show how to do an atomic write of the TCNT1 Register

contents. Writing any of the OCR1A/B or ICR1 Registers can be done by using the

same principle.

Note:

1. The example code assumes that the part specific header file is included.

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

be written to TCNT1.

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

written, 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.

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 81.

Counter Unit

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

counter unit. Figure 41 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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