Method and apparatus for synchronizing internal and external video signals

摘要

An automotive video display of a scene from a camera has a graphics window to display vehicle information. A video graphics controller has a programmable synchronous generator for the graphics window which is synchronized or gen-locked with the camera or external video signal. A digital sync separator provides digital external sync signals. A start circuit monitors the external sync signals to detect the start of a video frame and starts the sync generator which is initially in synchronism with the external signal. A phase locked loop maintains the synchronism. A crystal oscillator circuit includes an inductor and a varactor which is tuned to vary the oscillator frequency enough to track the external video signal.