PULSE-WIDTH MODULATION WAVEFORM GENERATOR

摘要

A PWM waveform generator has a cycle timer for generating pulses at regular intervals, and a duty timer for generating a pulse of a program-selected duration after each pulse from the cycle timer. A register stores one bit of data which designates whether the PWM output starts high or low at the beginning of each cycle. The pulses from the cycle timer are fed through gates controlled by the register contents to the set and reset terminals of a flip-flop. Pulses from the duty timer cause the flip-flop to toggle. The starting level can be changed in any PWM cycle by rewriting the data in the register.