Microprocessor and Controller

This document discusses pulse width modulation (PWM) modes in AVR microcontrollers. It describes fast PWM and phase correct PWM modes. For fast PWM, the timer counts from 0 to its maximum value and resets, generating a waveform at 1/256 the timer clock frequency. Duty cycle is set by comparing the counter to OCR0. For phase correct PWM, the timer counts up then down, generating a waveform at half the fast PWM frequency. Duty cycle is also set by comparing to OCR0. An example is given of configuring fast PWM to generate a 31.25 kHz waveform at 75% duty cycle using an 8 MHz clock.