ATmega88 datasheet(86/340 Pages) ATMEL

86 / 340 page

7530H–AVR–02/09

ATmega48/88/168 Automotive

12. 8-bit Timer/Counter0 with PWM

Timer/Counter0 is a general purpose 8-bit Timer/Counter module, with two independent Output

Compare Units, and with PWM support. It allows accurate program execution timing (event man-

agement) and wave generation. The main features are:

• Two Independent Output Compare Units

• Double Buffered Output Compare Registers

• Clear Timer on Compare Match (Auto Reload)

• Glitch Free, Phase Correct Pulse Width Modulator (PWM)

• Variable PWM Period

•Frequency Generator

• Three Independent Interrupt Sources (TOV0, OCF0A, and OCF0B)

12.1

Overview

A simplified block diagram of the 8-bit Timer/Counter is shown in Figure 12-1. For the actual

placement of I/O pins, refer to “Pinout ATmega48/88/168” on page 2. CPU accessible I/O Regis-

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

locations are listed in the “8-bit Timer/Counter Register Description” on page 97.

The PRTIM0 bit in “Power Reduction Register - PRR” on page 39 must be written to zero to

enable Timer/Counter0 module.

Figure 12-1. 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

Prescaler

T/C

Oscillator

clk

I/O

TOSC1

TOSC2

ATmega88 Datasheet(PDF) 86 Page - ATMEL Corporation

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