Abstract: A disk drive system has a closed loop servo control system which is specially tuned for optimal deceleration during performance of a track access operation. The servo control system is returned in response to a track jump signal to perform a track jump operation at a lesser deceleration and thereby reduce low frequency acoustic noise produced by physical vibrations of the disk drive system. The returning of the servo control system is advantageously achieved by reducing the gain-bandwidth product of the closed loop within the servo control system.

Abstract: A circuit for accurately detecting the number of tracks crossed by a reading head during motion thereof across a record medium uses a state machine operation to detect track crossing transitions and to suppress the effect of noise. The head produces a signal which assumes one of four unique states in sequence as successive tracks are crossed. The circuit detects a valid track crossing when a generated next state is the correct next state for a present state indicated by the signal.