Digital horizontal flyback control circuit
 A digital horizontal flyback control circuit for controlling the horizontal position of a video signal on a monitor screen receives a horizontal drive signal (21) and a flyback signal (22) generated when a video display beam is caused to move from the end of one line of the display to the beginning of a next line by an edge of a pulse of the horizontal drive signal, the flyback pulse being delayed with respect to the horizontal drive signal pulse by a flyback delay period. A measuring circuit (15) measures the flyback delay period and a subtractor circuit (17) subtracts the flyback delay from a set horizontal position (18) representing a desired delay between the flyback pulse and a reference pulse (11). A comparator (19) compares the subtraction value with the value of a clock counter (23) whose count value is reset by the reference pulse (11) and produces a set signal at an output when the subtraction value and the clock count value are the same so as to generate the horizontal drive signal pulse (21). 
Motorola, Inc.
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Yung-Jann Jerry
Chen