A decoding technique applicable to binary data encoded by phase encoding (PE), frequency modulation (FM), or modified frequency modulation (MFM). Resynchronization of the decoding clocking circuitry occurs upon every flux transition, rather than at less than all flux transitions, such as only at each data flux transition in the case of phase encoding. The technique provides substantially greater velocity tolerance than previous techniques for decoding codes encoded in this manner.
There is disclosed a signal transducer for extracting only the data components from information which has been modulated by different modulation systems. More concretely, the transducer provides two kinds of clock signals with respect to the information obtained by modulating the data under the frequency-modulation system or the modified frequency-modulation system, and extracts the data components from the information in accordance with one of the two kinds of clock signals.
An all digital method and apparatus for recovering NRZ information from MFM data wherein the MFM pulse stream is monitored through hypothetical windows, the receipt of a pulse during a particular window providing information about the data state(s) represented by the pulse and tracking adjustments required to recover subsequent pulses, and further wherein each window is divided into a large number of subinterval's so that the coincidence of a pulse with a particular subinterval provides information about the amount and direction by which the position of subsequent windows should be changed for tracking correction; the windows and subintervals being implemented by the execution of one of a number of step sequences, the particular step sequence being executed indicating the classification of a pulse received during the particular step sequence, and the step being executed at the time of receipt of the pulse indicating required tracking adjustments.
