Circuit and method for forming pulse train output in response to carry/borrow output of count pulse train

摘要

A circuit and method for forming a pulse train output in response to a carry/borrow signal from a calculation of an input pulse train are disclosed in which a plurality of sign-less adders/subtractors and a pulse train output generating circuit are installed. The input pulse train has an interval corresponding to a reference input quantity (0.3517 &mgr;m) which is less than a predetermined physical quantity (e.g. , 1 &mgr; m). Each pulse of the output pulse train has an interval corresponding to the predetermined physical quantity. The adder/subtractors carry out an addition or subtraction of two input numerical values, each numerical value corresponding to the reference unit quantity according to a direction of the input pulse train, whenever one input pulse is received. The pulse train output generating circuit generates the output pulse train, with each pulse interval corresponding to the physical quantity, in response to either, carry or, borrow signal derived as the result of an addition or a subtraction of the adder/subtractors. In the preferred embodiment, the number of the adder/subtractors corresponds to the number of digits in the reference unit quantity.