ATMEGA8535L-8AI datasheet(71/321 Pages) ATMEL

71 / 321 page

ATmega8535(L)

2502K–AVR–10/06

8-bit Timer/Counter0

with PWM

Timer/Counter0 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

• External Event Counter

• 10-bit Clock Prescaler

• Overflow and Compare Match Interrupt Sources (TOV0 and OCF0)

Overview

A simplified block diagram of the 8-bit Timer/Counter is shown in Figure 27. For the

actual placement of I/O pins, refer to “Pinout ATmega8535” 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

page 83.

Figure 27. 8-bit Timer/Counter Block Diagram

Registers

The Timer/Counter (TCNT0) and Output Compare Register (OCR0) are 8-bit registers.

Interrupt request (abbreviated to Int.Req. in the figure) 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 by an external clock

source on the T0 pin. The Clock Select logic block controls which clock source and edge

the Timer/Counter uses to increment (or decrement) its value. The Timer/Counter is

inactive when no clock source is selected. The output from the Clock Select logic is

referred to as the timer clock (clk

T0).

Timer/Counter

TCNTn

Waveform

Generation

OCn

= 0

Control Logic

= 0xFF

BOTTOM

count

clear

direction

TOVn

(Int.Req.)

OCRn

TCCRn

Clock Select

Edge

Detector

( From Prescaler )

clkTn

TOP

OCn

(Int.Req.)

ATMEGA8535L-8AI Datasheet(PDF) 71 Page - ATMEL Corporation

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