Patent ID: 6822492
Filing Date: 2004-11-23
Classification: G06F

Abstract:
A variable-frequency pulse generator which executes one cycle of output control of the pulse train by two cycles of a reference clock, comprising:an inversion unit which inverts a first reference value regulated by the reference clock; a selection unit which selects the first reference value after inversion, when an overflow has occurred, and in any other event selects a predetermined value which changes depending on a set speed; a data holding unit which latches an output of a previous stage, being the present value of a result of addition, in the second cycle of the reference clock and at a predetermined timing of an overflow prevention signal; an addition unit which adds the value selected by the selection unit and the data latched by the data holding unit; a first comparison unit which compares the value obtained by the addition unit as a result of addition and the first reference value; a second comparison unit which compares the value obtained by the addition unit as a result of addition and a second reference value which is half of the first reference value; a judgment unit which judges whether a condition â€œ0&lE;addition resulta pulse train output unit which latches the specified signal at a predetermined timing of the second cycle of the reference clock, and outputs a pulse train of a desired frequency; a third comparison unit which compares the data latched by the data holding unit and the first reference value, and when a condition â€œlatched data&gE;first reference valueâ€  is satisfied, judges that the overflow has occurred; and an overflow prevention unit which outputs the overflow prevention signal at a predetermined timing of the first cycle of the reference clock, when the third comparison unit has judged that the overflow has occurred.