Honeywell Information Systems Italia

Bonifacio Troletti

A digital data separator for use with apparatus for recovering binary information recorded on a movable media in frequency modulation (FM) or modified frequency modulation (MFM) comprises a measurement unit which for each read pulse received as an input provides a code representing the actual duration of an interval N between read pulse n and the preceding read pulse n-1 and a speed error correction unit which corrects an actual interval duration relative to the speed error of the movable media. The separator further includes a peak-shift recovery unit which provides as an output, nominal duration information related to interval N based on the corrected interval duration and on the peak-shift of pulse n-1, determined by taking into account the corrected duration of an interval N-1, a preceding interval N, and the nominal duration of intervals N-1 and N-2 preceding interval N.

Digital data separator

A digital data separator for use with apparatus for recovering binary information recorded in FM or MFM on magnetic media comprises a measuring unit which in correspondence with a read pulse n, supplies information representative of the actual duration of interval N between pulse n and the previous read pulse n-1. A media speed error recovery unit corrects such duration relative to the nominal speed according to a code representative of the media speed error, a peak-shift recovery unit which depending on the peak-shift of pulse n-1, determined on the basis of the temporal history of the most recent pulses n-3, n-2 and n-1 of such corrected duration, supplies duration information related to such interval and information representative of the direction and the entity of the peak-shift of the read out pulse n, and a speed error measuring unit defines a code representative of such error as the difference between the actual duration of a period consisting of a suitable number of subsequent intervals between read pulses and their nominal duration. This duration is corrected relative to the peak-shift of the pulses defining the beginning and the end of the period and is further 'normalized' according to the nominal duration of the period. The speed error code is applied to the speed error recovery unit. The nominal duration of interval N is applied to a logic unit which generates a 'window' signal and reconstructs the read pulse in a suitable phase relationship with the window signal.

A digital apparatus for data recovery system wherein data is recorded in FM or MFM code on magnetic media, comprises a measuring unit that in correspondence of a read pulse n as an input, supplies as an output, information related to the actual duration of interval N between pulse n and the previous read pulse n-1. A recovery unit for the magnetic media speed error relative to a nominal speed corrects the duration according to a code representative of the magnetic media speed error and a peak shift recovery unit which, according to the peak shift of pulse n-1, determined on the basis of the time history of the most recent pulses n-2, n-3, n-1 and the corrected duration, supplies as an output, nominal duration information related to this corrected duration and information representative of the direction and the amount of the peak shift of said read out pulse N-7. A measuring unit of speed error defines a code representative of the error as a function of the peak shift direction of a suitable number of subsequent read out pulses and a previously measured speed error which is fed to the speed error recovery unit. The nominal duration information is applied to the input of a logic unit for generating a 'window' signal and reconstructing the read pulse in suitable phase relationship with the window signal.

Digital apparatus for data recovery system

A digital apparatus recovers data recorded in FM or MFM on a magnetic media moving at a normal speed in which the reading of the media provides a sequence of timing/data pulses at variable intervals, which differ from a nominal interval due to speed error and magnetic 'peak-shift'. The apparatus provides identification of a nominal interval between read out pulses and the reconstruction of a correct stream of pulses properly located within a window signal. It includes a digital measurement unit which at each read out pulse n received in input supplies at an output a code indicative of the actual duration of the interval N between the pulse n and a previous pulse n-1; and a speed correction unit which corrects the measured duration of the interval N relative to speed error detected by the digital measurement unit during reading of a synchronization bit field. A peak shift correction unit included within the apparatus utilizing the corrected interval duration, and for MFM recording, the previous most recent history of received pulses establishes a nominal duration for the interval N. The nominal duration attributed to interval N is used by a regeneration unit to produce a suitable window signal and a regenerated pulse corresponding to the read out n pulse which is properly located within the window signal.

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Boario Terme, Italy

Bonifacio Troletti