ATtiny44 datasheet(106/236 Pages) ATMEL

106 / 236 page

106

8006H–AVR–10/09

ATtiny24/44/84

Note:

See “Code Examples” on page 6.

The assembly code example returns the TCNT1 value in the r17:r16 register pair.

It is important to notice that accessing 16-bit registers are atomic operations. If an interrupt

occurs between the two instructions accessing the 16-bit register, and the interrupt code

updates the temporary register by accessing the same or any other of the 16-bit timer registers,

then the result of the access outside the interrupt will be corrupted. Therefore, when both the

main code and the interrupt code update the temporary register, the main code must disable the

interrupts during the 16-bit access.

The following code examples show how to do an atomic read of the TCNT1 Register contents.

Reading any of the OCR1A/B or ICR1 Registers can be done by using the same principle.

Assembly Code Examples

...

; Set TCNT

1 to 0x01FF

ldi

r17,0x01

ldi

r16,0xFF

out

TCNT

1H,r17

out

TCNT

1L,r16

; Read TCNT

1 into r17:r16

r16,TCNT

r17,TCNT

...

C Code Examples

unsigned int

...

/* Set TCNT

1 to 0x01FF */

TCNT

1 = 0x1FF;

/* Read TCNT

1 into i */

i = TCNT

...

Assembly Code Example

TIM16_ReadTCNT

; Save global interrupt flag

r18,SREG

; Disable interrupts

cli

; Read TCNT

1 into r17:r16

r16,TCNT

r17,TCNT

; Restore global interrupt flag

out

SREG,r18

ret

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