ATmega162 datasheet(138/324 Pages) ATMEL

138 / 324 page

138

2513K–AVR–07/09

ATmega162/V

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 and OCF2)

• 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 place-

ment of I/O pins, refer to “Pinout ATmega162” 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 Register and bit loca-

tions are listed in the “8-bit Timer/Counter Register Description” on page 149.

Figure 59. 8-bit Timer/Counter Block Diagram

Registers

The Timer/Counter (TCNT2) and Output Compare Register (OCR2) are 8-bit registers. Interrupt

request (shorten as Int.Req.) signals are all visible in the Timer Interrupt Flag Register (TIFR).

All interrupts are individually masked with the Timer Interrupt Mask Register (TIMSK). TIFR and

TIMSK are not shown in the figure since these registers are shared by other timer units.

The Timer/Counter can be clocked internally, via the prescaler, or asynchronously clocked from

the TOSC1/2 pins, as detailed later in this section. The asynchronous operation is controlled by

Timer/Counter

TCNTn

Waveform

Generation

OCn

= 0

Control Logic

= 0xFF

TOP

BOTTOM

count

clear

direction

TOVn

(Int.Req.)

OCn

(Int.Req.)

Synchronization Unit

OCRn

TCCRn

ASSRn

Status flags

clk

I/O

clk

ASY

Synchronized Status flags

asynchronous mode

select (ASn)

TOSC1

T/C

Oscillator

TOSC2

Prescaler

clk

I/O

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