Registers – Coded record sensors – Particular sensor structure
Patent
1996-02-15
1998-07-14
Hajec, Donald T.
Registers
Coded record sensors
Particular sensor structure
235486, 360113, G06K 708, G06K 700, G11B 5127
Patent
active
057808287
ABSTRACT:
A method and apparatus for reading and writing data to a medium which moves at an uncontrolled velocity relative to a read/write apparatus with which the data is read and written. The read/write apparatus comprises one write head and two read heads. The first read head is spaced apart from the second read head by an odd integer multiple of one half of a bit cell. The two read heads read preexisting data from the medium and generate a write clock which is used to synchronize a write operation using the write head. Delay logic ensures that the write head is over that portion of the medium on which new data is to be written. By measuring the amount of time between detection of a transition at the first read head and detection of that transition at the second read head, the velocity of the medium with respect to the read/write apparatus is determined and the amount of time that must elapse between the reading of old data and the writing of new data which overwrites the old data is determined. A write clock decoder receives a pulse associated with each transition read by either the first or the second read head, and outputs a write clock synchronized to the velocity of the read/write apparatus with respect to the medium based upon these received pulses. By spacing the two read heads apart by an odd multiple of one half the bit cell, either the first or the second read head will always detect a transition at each half bit cell. Thus, the write clock will have a transition each half bit cell.
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Mos Robert
Mueller Clay Von
DH Technology Inc.
Hajec Donald T.
Le Thien Minh
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