ATMEGA640 datasheet(181/436 Pages) MICROCHIP

Part #	ATMEGA640

Description	8-bit Microcontroller with 16/32/64KB In-System Programmable Flash

PDF	436 Pages

Scroll/Zoom	100%

Manufacturer	MICROCHIP [Microchip Technology]

Direct Link	http://www.microchip.com

Logo

181 / 436 page

181

ATmega640/V-1280/V-1281/V-2560/V-2561/V [DATASHEET]

DS40002211A

The clock source for Timer/Counter2 is named clkT2S. clkT2S is by default connected to the main system I/O clock

clkIO. By setting the AS2 bit in ASSR, Timer/Counter2 is asynchronously clocked from the TOSC1 pin. This

enables use of Timer/Counter2 as a Real Time Counter (RTC). When AS2 is set, pins TOSC1 and TOSC2 are dis-

connected from Port C. A crystal can then be connected between the TOSC1 and TOSC2 pins to serve as an

independent clock source for Timer/Counter2. The Oscillator is optimized for use with a 32.768kHz crystal. By set-

ting the EXCLK bit in the ASSR, a 32kHz external clock can be applied. See “ASSR – Asynchronous Status

For Timer/Counter2, the possible prescaled selections are: clkT2S/8, clkT2S/32, clkT2S/64, clkT2S/128, clkT2S/256, and

clkT2S/1024. Additionally, clkT2S as well as 0 (stop) may be selected. Setting the PSRASY bit in GTCCR resets the

prescaler. This allows the user to operate with a predictable prescaler.

ATMEGA640 Datasheet(PDF) 181 Page - Microchip Technology