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Group coded recording data recovery system

  • US 4,219,851 A
  • Filed: 11/24/1978
  • Issued: 08/26/1980
  • Est. Priority Date: 11/24/1978
  • Status: Expired due to Term
First Claim
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1. A digital data recovery system controlled by a system clock for decoding GCR input data bits stored on magnetic media in the form of flux reversals with no more than two successive zeros throughout a data record, comprising:

  • a first means for monitoring an input data signal from a magnetic storage media for flux reversals and generating an EDGE signal for each transition of the input data;

    a second means responsive to said EDGE signal for enabling the data recovery system when a predetermined number of said EDGE signals have been received and for generating a HLF-EDGE signal when a transition occurs during the first half clock cycle;

    a third means responsive to said EDGE signal and a ZONE signal representing the average data rate in clock periods between previous output data bits for comparing the incoming signal with previous output data to signal when to output a data bit as via a RDY-OUT signal and what logical state to give it via a ONE-FF signal;

    a fourth means responsive to said RDY-OUT signal for generating a ZONE signal representing the average time between a predetermined number of previous output data bits;

    an output means responsive to said EDGE, RDY-OUT, ONE-FF and HLF-EDGE signals for generating an output data bit from said ONE-FF signal and a strobe signal $MRK from said RDY-OUT signal and for generating an error condition pointer signal PNTR and a strobe signal $MRK when a predetermined condition exists between the input data represented by EDGE and HLF-EDGE and the output data represented by RDY-OUT.

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