Flexible video synchronization circuit
AssigneeNicolet Instrument Corporation
InventorsPatrick Mulvanny, Scott Bartky
Life of this patent
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Abstract
A circuit which accepts a variable horizontal frequency input signal and an independent variable vertical frequency input signal and generates a combined video synchronization signal including horizontal synchronization pulses and serrated vertical synchronization pulses preceded and followed by equalization pulses in accordance with specifications established by the National Television Standards Committee. The circuit is useful for generating a combined video synchronization signal from the variable frequency horizontal and vertical synchronization pulses supplied by programmable cathode ray tube controller integrated circuits.
Claims9
A circuit for accepting a horizontal frequency input signal and a vertical frequency input signal and generating a combined video synchronization signal, comprising, in combination:
- (a) a phase-locking means having an input accepting the horizontal frequency input signal for generating a plurality of phases at the horizontal input frequency;
- (b) delay means for receiving the vertical input frequency and having outputs providing consecutive early, current, and late vertical sync pulses;
- and
- (c) a combinatorial logic means, having combinatorial logic gates with inputs accepting a plurality of the phases at the horizontal input frequency and the consecutive early, current, and late vertical sync pulses, for generating a composite video synchronization signal having both the horizontal and the vertical synchronization frequencies, and having only one phase of the horizontal input frequency in the absence of the consecutive early, current, and late vertical sync pulses, and having at least two phases of the horizontal input frequency during the consecutive early and late vertical sync pulses, so that a composite video synchronization signal is generated having horizontal pulses, serrated vertical pulses, and equalization pulses at twice the horizontal frequency preceding and following the serrated vertical pulses.
Dependencies are inferred from the claim text.