ATMEGA640 datasheet(176/449 Pages) ATMEL

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176

ATmega640/1280/1281/2560/2561

2549K–AVR–01/07

8-bit Timer/Counter2 with PWM and Asynchronous Operation

Timer/Counter2 is a general purpose, single channel, 8-bit Timer/Counter module. The

main features are:

• Single Channel Counter

• Clear Timer on Compare Match (Auto Reload)

• Glitch-free, Phase Correct Pulse Width Modulator (PWM)

• Frequency Generator

• 10-bit Clock Prescaler

• Overflow and Compare Match Interrupt Sources (TOV2, OCF2A and OCF2B)

• Allows Clocking from External 32 kHz Watch Crystal Independent of the I/O Clock

Overview

A simplified block diagram of the 8-bit Timer/Counter is shown in Figure 59.. For the

actual placement of I/O pins, see “Pin Configurations” on page 2. CPU accessible I/O

Registers, including I/O bits and I/O pins, are shown in bold. The device-specific I/O

The Power Reduction Timer/Counter2 bit, PRTIM2, in “PRR0 – Power Reduction Regis-

ter 0” on page 55 must be written to zero to enable Timer/Counter2 module.

Figure 66. 8-bit Timer/Counter Block Diagram

Timer/Counter

OCRnA

OCRnB

TCNTn

Waveform

Generation

Waveform

Generation

OCnA

OCnB

Fixed

TOP

Value

Control Logic

= 0

TOP

BOTTOM

Count

Clear

Direction

TOVn

(Int.Req.)

OCnA

(Int.Req.)

OCnB

(Int.Req.)

TCCRnA

TCCRnB

clk

ASSRn

Synchronization Unit

Prescaler

T/C

Oscillator

clk

I/O

clk

ASY

asynchronous mode

select (ASn)

Synchronized Status flags

TOSC1

TOSC2

Status flags

clk

I/O

ATMEGA640 Datasheet(PDF) 176 Page - ATMEL Corporation

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