SYNC SIGNAL GENERATOR OF IMAGE APPARATUS

摘要

A synchronous signal generator includes a head detector for detecting the head of a external composite synchronous signal, an external synchronous signal input detector for generating an external synchronous signal input detection signal for judging whether the external synchronous signal is inputted, an external vertical synchronous signal head detector for counting the pulse width of the external synchronous pulses with a clock signal and detecting the head of the external vertical synchronous signal according to the counted value, a horizontal synchronous signal generator for counting the clock signal and decoding the counted value to generate a horizontal synchronous signal and horizontal blanking signal, a vertical synchronous signal generator for counting the head signal of the horizontal synchronous signal and decoding the counted value to generate a vertical synchronous signal and vertical blanking signal, a signal combiner for combining the horizontal and vertical synchronous signals to generate an inner composite synchronous signal and combining the horizontal and vertical blanking signals to generate a blanking signal, and a synchronous signal selector for selectively outputting the external and inner composite synchronous signals.