ATMEGA640 datasheet(140/449 Pages) ATMEL

Part #	ATMEGA640

Description	8-bit Microcontroller with 64K/128K/256K Bytes In-System Programmable Flash

PDF	449 Pages

Scroll/Zoom	100%

Manufacturer	ATMEL [ATMEL Corporation]

Direct Link	http://www.atmel.com

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140 / 449 page

140

ATmega640/1280/1281/2560/2561

2549K–AVR–01/07

Note:

1. See “About Code Examples” on page 9.

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

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

rupt 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 regis-

ter, the main code must disable the interrupts during the 16-bit access.

Assembly Code Examples

(1)

...

; 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 Examples(1)

unsigned int

...

/* Set TCNTn to 0x01FF */

TCNTn = 0x1FF;

/* Read TCNTn into i */

i = TCNTn;

...

ATMEGA640 Datasheet(PDF) 140 Page - ATMEL Corporation