Self-clocking NRZ recording and reproduction system
AssigneeGeneral Instrument Corporation
InventorsRonald P. McGrath, William A. Bleher
Life of this patent
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Abstract
A magnetic recording and reading system wherein data is written into a magnetic medium in an NRZ code which is interrupted for the insertion of a guaranteed flux transition after each series of eight data cells. On readout, the guaranteed sync transition is used to generate a read clock for strobing purposes. The read clock is compensated to account for physical migration of the sync transition in the medium due to crowding effects or interaction with adjacent flux transitions.
Claims14
In a data storage system of the type wherein data is stored in a bulk medium according to a binary code in which opposite bit values are represented in bit cells by respective levels and wherein the sync transition occurs every n data bit cells:
- a readout system comprising clock means responsive to the occurrence of a sync transition for generating a sequence of timing signals representing the position in time of successive data cells being read, means for reading the bit values in the successive bit cells, means for counting the successive bit cells to identify each occurrence of n data bit cells, and compensation means responsive to particular patterns of the level transitions associated with the data cells preceding and following each identified sync transition of n data bit cells for adjusting the time relationship between the sync transition and said sequence of reading the bit values in the successive bit cells in accordance with such particular patterns to compensate for shifting of said sync transition as read from said medium by said readout system.
In a magnetic data storage system of the type wherein data is stored in a bulk medium according to a binary code in which opposite bit values are represented in bit cells by respective flux levels and wherein the sync flux transition occurs every n data bit cells:
- a readout system comprising clock means responsive to the occurrence of a sync transition for generating a sequence of time signals representing the position in time of successive data cells being read, and compensation means responsive to the flux level transitions associated with the data cells preceding and following the sync transition for adjusting the time relationship between the sync transition and said sequence to compensate for shifting of said sync transition in said medium, the compensation means comprising a plurality of delay means having inputs connected to receive said sync flux transitions and outputs connected to said clock means and representing respective time delays, decoder means responsive to data and sync transitions for producing output signals representing sync transition shifts, and logic means responsive to the output signal from said decoder means to operatively connect one of said plurality of delay means in operative input relationship with said clock means to select a time delay for compensation of the sync transition shift.
In combination for use with apparatus for storing bit values in bit cells wherein changes in bit values are represented by changes in voltage levels and wherein a sync transition is provided every n bit cells,
- first means for reading the voltage levels to reproduce the bit values,
- second means for counting the bit cells to produce a signal indicating each sync transition of n bit cells,
- third means responsive to the operation of the first and second means for producing clock signals to synchronize the operation of the first and second means, and
- fourth means responsive to the bit values read by the first means in the bit cells immediately preceding and immediately following each signal produced by the second means for adjusting the time for the production by the third means of the clock signals in accordance with the relative bit values in such immediately preceding and immediately following bit cells.
Dependencies are inferred from the claim text.