Abstract: A serial bus clock frequency calibration system and a method thereof are disclosed herein. The system utilizes a first frequency calibration device and a second frequency calibration device both to share an oscillator as so to perform two-stage clock frequency resolution calibrations for generating different frequency-tuning ranges. This can bring an optimal frequency resolution and greatly reduce system complexity and save element cost.

Abstract: A serial bus clock frequency calibration system and a method thereof are disclosed herein. The system utilizes a first frequency calibration device and a second frequency calibration device both to share an oscillator as so to perform two-stage clock frequency resolution calibrations for generating different frequency-tuning ranges. This can bring an optimal frequency resolution and greatly reduce system complexity and save element cost.

Abstract: In the preferred embodiment, the RGB analog signals generated by a VGA card in a personal computer are applied to a first input of an analog multiplexer. The digital video data stored in a video memory buffer on a video card is converted to RGB analog signals using a D/A converter, and these analog signals are applied to a second input of the analog multiplexer. An analog comparator compares a preselected color key to the analog output of the VGA card. When there is a match, the analog comparator controls the multiplexer to pass the analog video data to the monitor for display. When the color key is not detected, the data from the VGA card is transmitted to the monitor for display. Other features for improving the video overlay precision and the quality of the displayed image are also described.