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Browse Prior Art Database

Method of Data Separation for MFM

IP.com Disclosure Number: IPCOM000091369D
Original Publication Date: 1968-Jan-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Franchini, RC: AUTHOR [+3]

Abstract

In a method of data separation, as shown by the upper three waveforms, data is normally detected by the occurrence of data bit 10 during a data window. The data window normally comprises VFO phase 11 which is one half the period of a complete VFO oscillation. However, in some instances, the allowable bit shift of a data bit in either direction, shown by bits 12 and 13, results in a total span broader than the data window. An approach utilized previously to allow recognition of such shifted data bits comprises widening of the data window beyond the 180 degrees of the VFO trigger. Such an expanded data window is shown by waveform 14. In the lower drawings, an alternative method utilizes the 180 degrees VFO phase 11 as before and changes the time constant of the data bit detection circuitry.

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Method of Data Separation for MFM

In a method of data separation, as shown by the upper three waveforms, data is normally detected by the occurrence of data bit 10 during a data window. The data window normally comprises VFO phase 11 which is one half the period of a complete VFO oscillation. However, in some instances, the allowable bit shift of a data bit in either direction, shown by bits 12 and 13, results in a total span broader than the data window. An approach utilized previously to allow recognition of such shifted data bits comprises widening of the data window beyond the 180 degrees of the VFO trigger. Such an expanded data window is shown by waveform 14. In the lower drawings, an alternative method utilizes the 180 degrees VFO phase 11 as before and changes the time constant of the data bit detection circuitry. This alteration to the circuitry widens the output from it, as shown by pulse 15, so as to be sufficiently wide to extend into the data window even though occurring at the maximum bit shift in either direction, as shown by pulse 16 and 17.

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