ATmega16HVB datasheet(91/273 Pages) ATMEL

91 / 273 page

8042A–AVR–07/09

ATmega16HVB/32HVB

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 OCRnA/B registers.

Note:

1. See “About Code Examples” on page 8.

The assembly code example returns the TCNTnH/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 TCNTn to 0x01FF

ldi

r17,0x01

ldi

r16,0xFF

out

TCNTnH,r17

out

TCNTnL,r16

; Read TCNTn into r17:r16

r16,TCNTnL

r17,TCNTnH

...

C Code Example

unsigned int

...

/* Set TCNTn to 0x01FF */

TCNTn = 0x1FF;

/* Read TCNTn into i */

i = TCNTn;

...

ATmega16HVB 数据表(PDF) 91 Page - ATMEL Corporation

ATmega16HVB 数据表(HTML) 91 Page - ATMEL Corporation

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