Browse Prior Art Database

Mfm Data Marginalization

IP.com Disclosure Number: IPCOM000044633D
Original Publication Date: 1984-Dec-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Duffee, TM: AUTHOR [+3]

Abstract

The circuitry shown above in combination with the procedure described below can be used to increase the efficiency and reduce the cost of disk surface analysis. This procedure marginalizes the phase relationship of data to its window and can be used with existing VFO design. The circuitry shown above can be used as part of the manufacturing test procedure, or can be permanently incorporated and used under system program control. The present procedure uses the VFO "Address Mark Found" signal to enable a delay to be inserted in alternating date pulses that are being sent from file. When the delay is inserted in the commonly used tri-bit pattern (worst-case peak shift pattern), media problems can be revealed by CRC (cyclic redundancy check) errors.

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Mfm Data Marginalization

The circuitry shown above in combination with the procedure described below can be used to increase the efficiency and reduce the cost of disk surface analysis. This procedure marginalizes the phase relationship of data to its window and can be used with existing VFO design. The circuitry shown above can be used as part of the manufacturing test procedure, or can be permanently incorporated and used under system program control. The present procedure uses the VFO "Address Mark Found" signal to enable a delay to be inserted in alternating date pulses that are being sent from file. When the delay is inserted in the commonly used tri-bit pattern (worst-case peak shift pattern), media problems can be revealed by CRC (cyclic redundancy check) errors. To vary the peak shift in both directions, the pattern is rewritten and alternate bits are shifted one, but starting with the first bit in one pass and then the second bit on the second pass. The circuitry is designed so as to allow the operator to select the delay time in increments of approximately 3.75 nanoseconds. For example, if one passes the alternating bits through one delay path, the bit will be delayed
3.75 nanoseconds, while if the operator selects 12 delay paths, the bit will be delayed 12 x 3.75, or 45 nanoseconds. Thus, using the above method under program control, an operator can totally map the track surface of a disk.

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