| 摘要 |
In a data recovery system, encoded variable spaced digital data is recovered by provision of variable width windows which are expanded or narrowed so as to tend to center upon the expected occurrence of valid data based on knowledge of the contents of the current or the immediately preceding timing units and of characteristics of the encoding scheme. The system employs pulse-to-pulse synchronization without modifying the underlying synchronization of the system such that the first pulse of a two-pulse series serves as a window size reference for an immediately subsequent pulse. The window for a reference pulse is expanded at its trailing edge if, for example, the reference pulse is delayed beyond the tolerance of the detection system. The leading edge of a window for the subsequent pulse is expanded if no pulse occurs within a minimum period following the reference pulse. The encoding technique is particularly applicable to data storage and retrieval systems employing Modified Frequency Modulation (MFM) coding as commonly used in disk drive systems communicating with an input and output controller of a computer.
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