SYNC SEPARATOR WITH PERIODIC UPDATING

摘要

A sync separator detects the occurrence of a corresponding sync pulse in a corresponding part of the waveform of a composite video signal. The level of the sync tip is used for updating a sync tip signal, provided the level of the sync tip is lower than that of the sync tip signal. A time-out signal is generated at the end of a time-out interval that has elapsed from the last time the sync tip signal was updated, provided the sync tip signal was not updated within such time-out interval. The time-out signal is used for updating the sync tip signal. The sync tip signal is updated according to such sync pulse that occurred during the time-out interval, having the lowest level sync tip. Information obtained from the sync tip and the back porch portions of the corresponding sync pulse is used for generating a slice level signal. A comparator responsive to the slice level signal separates a sync signal from the composite video signal.