ATtiny261A datasheet(107/292 Pages) ATMEL

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107

8197A–AVR–10/09

ATtiny261A/461A/861A

12.11.2

Code Examples

The following code examples show how to access the 10-bit timer registers assuming that no

interrupts updates the TC1H register. The same principle can be used directly for accessing the

OCR1A/B/C/D registers.

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 10-bit registers are atomic operations. If an interrupt

occurs between the two instructions accessing the 10-bit register, and the interrupt code

updates the TC1H register by accessing the same or any other of the 10-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 TC1H register, the main code must disable the interrupts

during the 16-bit access.

Assembly Code Example

...

; Set TCNT

1 to 0x01FF

ldi

r17,0x01

ldi

r16,0xFF

out

1H,r17

out

TCNT

1,r16

; Read TCNT

1 into r17:r16

r16,TCNT

r17,TC

...

C Code Example

unsigned int

...

/* Set TCNT1 to 0x01FF */

TC1H = 0x01;

TCNT1 = 0xFF;

/* Read TCNT1 into i */

i = TCNT1;

i |= ((unsigned int)TC1H << 8);

...

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