ATtiny261-ESSZ datasheet(82/227 Pages) ATMEL

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7753C–AVR–07/09

ATtiny261/ATtiny461/ATtiny861

The following code examples show how to access the 16-bit timer registers assuming that no

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

the OCR0A/B registers.

Note:

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

For I/O registers located in extended I/O map, “IN”, “OUT”, “SBIS”, “SBIC”, “CBI”, and “SBI”

instructions must be replaced with instructions that allow access to extended I/O. Typically

“LDS” and “STS” combined with “SBRS”, “SBRC”, “SBR”, and “CBR”.

The assembly code example returns the TCNT0H/L 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.

Assembly Code Example

...

; Set TCNT0 to 0x01FF

ldi

r17,0x01

ldi

r16,0xFF

out

TCNT

0H,r17

out

TCNT

0L,r16

; Read TCNT

0 into r17:r16

r16,TCNT

r17,TCNT

...

C Code Example

unsigned int

...

/* Set TCNT0 to 0x01FF */

TCNT0H = 0x01;

TCNT0L = 0xff;

/* Read TCNT0 into i */

i = TCNT0L;

i |= ((unsigned int)TCNT0H << 8);

...

ATtiny261-ESSZ Scheda tecnica(PDF) 82 Page - ATMEL Corporation

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