Abstract: There is disclosed herein a servo data decoder which can decode both quadrature and non quadrature servo data. The decoder is comprised of a servo data amplitude demodulator to generate position error signals and a position error signal processor to generate a GPES signal to serve as a position error signal during the track following mode and a velocity signal and a track crossing signal for use in the seek mode. The user system may have either single or double pulse sync, and double pulse sync spacing, pulse window time and sync to first data pulse delay are user definable. The user may adjust the gain of the system in two manners and may program the frequency response characteristics of the phase locked loop. Many other user definable or user alterable features are provided.

Abstract: There is disclosed herein a servo data demodulator for use in magnetic head positioning servo system for disk drives. The demodulator is comprised of a single peak detector which detects the maximum amplitude of the peaks in an input signal during specific times. A storage capacitor is used in the peak detector to store the peak level. This peak level is sampled a predetermined number of times during each data frame. Each sample is taken by a different sample and hold circuit, and the sequence of the samples is controlled by a timing generator. The capacitor of the peak detector is discharged by a switch controlled by the timing generator after each sample and before the next sample. The time delay before the first sample from the start of the frame and the sample time in the sequence is programmable by the user by setting certain inputs into the timing generator.