Browse Prior Art Database

Magnetic Media Write Verification

IP.com Disclosure Number: IPCOM000077406D
Original Publication Date: 1972-Jul-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Everett, LH: AUTHOR [+2]

Abstract

A single magnetic head gap may write data on media and simultaneously verify that the data has actually been written.

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Magnetic Media Write Verification

A single magnetic head gap may write data on media and simultaneously verify that the data has actually been written.

Data signals supplied to magnetic write heads do not always result in recorded data signals. In the case of magnetic tape, failure to write may result from tape creasing, oxide voids, dust or lint, head lift-off, etc. Traditional verification requires a separate reading head or gap, physically separated from the writing gap. This does not give an immediate indication of a failure to write, requires wastefully large interblock data gaps to accommodate the verification delay, introduces write-to-read feedthrough, etc.

Fig. 1a shows a typical 30 mv data signal supplied to write heads in Figs. 2 and 3. with 3 mv perturbations caused by defects during writing. Fig. 1b, alternatively, shows an exaggerated amplitude envelope of write data signals which may be supplied to write heads in Figs. 2 and 3.

Correct writing normally occurs in the absence of the defects listed above, as shown by the level portion of the Fig. la data signal and Fig. 1b envelope. Defects cause modulation on the order of a few percent of the envelope, because they change the write head gap-media reluctance which is reflected as a head winding impedance change.

In Fig. 2, a change in gap-media separation from A to B causes the amplifier output to vary as a function of the winding impedance change. The presence of this data signal perturbation (Fig. 1...