Patent ID: 7071741

Claim:
A method for generating an output signal at a frequency that is N times a frequency of an input signal and phase-locked to said input signal, comprising the steps of: providing processing means having (i) a digital timer adjustable to operate at a known timer clock rate to generate an overflow signal each time said digital timer counts to a count value CV at said tinier clock rate, and (ii) a plurality of interrupts to include a first interrupt having a first time window associated therewith during which processing occurs and a second interrupt having a second time window associated therewith during which processing occurs, said first time window definable by a first number of counts C 1 of said digital timer and said second time window definable by a second number of counts C 2 of said digital timer; determining said count value CV based on a desired frequency multiplier N, said timer clock rate, and time required for one cycle of said input signal, wherein said overflow signal is generated N times for said one cycle and wherein said count value CV is greater than (C 1 +C 2 ) such that said first time window and said second time window begin and elapse in a non-overlapping fashion during the time it takes for said digital timer to count to said count value CV; selecting an interim count IC that defines a number of counts counted by said digital timer before said digital timer counts to said count value CV; initializing said digital timer such that said first time window begins at a timer count TC of said digital timer defined as TC=IC−0.5(C 1 ), wherein said first time window is approximately centered at said interim count IC and wherein said first time window and said second time window do not overlap; using said one cycle of said input signal to trigger said first interrupt, at which point said first time window begins; using said overflow signal to trigger said second interrupt, at which point said second time window begins; and modifying, during the occurrence of said second time window, said count value CV to maintain said first time window approximately centered at said interim count IC.