Write clock signal generator for use with rotating magnetic memory

Abstract

A system for generating a write clock signal for use with a rotating magnetic memory apparatus, such as a disk memory, in a data processing system which includes a slotted disk transducer which produces an intermediate pulse signal having a repetition rate related to the disk speed, a freqency-locked loop which produces a write clock pulse output signal having a repeptition rate related to the intermediate repetition rate independently of variations in the disk speed. The time response of the loop can be relatively low to lock the write clock output signal frequency to relatively slow variations in the intermediate frequency and to avoid locking to any extraneous high frequency variations therein. A coded slot region provides a coded pulse sequence, having selected pulses missing therefrom which can be decoded for providing an index pulse, the missing pulses being supplied to the pulses from the transducer to form the intermediate pulse signal. A sector identifying pulse signal can also be obtained from the intermediate pulse signal.