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Contaminated Media Sense Circuit

IP.com Disclosure Number: IPCOM000107454D
Original Publication Date: 1992-Feb-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 1 page(s) / 61K

Publishing Venue

IBM

Related People

Vinh, P: AUTHOR

Abstract

A contaminated (defective) diskette can cause loss of data on the media and damage to the floppy diskette drive (FDD). When the contaminated sectors are encountered, the READ signal is LOW or null. In most FDD, the lower head is displaced a number of tracks toward the spindle motor against upper head. Therefore, the possibility for both heads to encounter contaminated sectors at the same time is very minimal. Both heads will perform READ/WRITE when they are enabled. However, only the head on the non-selected side is in a READ mode and can sense the flux transition on the media. Based on the above observation, the Media Sense Circuit, which is described as follows, can be implemented in the FDD to detect contaminated media. (Step1) Subtract the READ head signal of upper head to lower head using using difference amplifier circuit.

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Contaminated Media Sense Circuit

      A contaminated (defective) diskette can cause loss of data on
the media and damage to the floppy diskette drive (FDD). When the
contaminated sectors are encountered, the READ signal is LOW or null.
In most FDD, the lower head is displaced a number of tracks toward
the spindle motor against upper head. Therefore, the possibility for
both heads to encounter contaminated sectors at the same time is very
minimal. Both heads will perform READ/WRITE when they are enabled.
However, only the head on the non-selected side is in a READ mode and
can sense the flux transition on the media. Based on the above
observation, the Media Sense Circuit, which is described as follows,
can be implemented in the FDD to detect contaminated media.
(Step1) Subtract the READ head signal of upper head to lower head
using using difference amplifier circuit.
(Step2) The output of the difference amplifier circuit will be
amplified and sampled through a peak detector circuit.
(Step3) Output of step2 will be compared with the set reference
level. This reference level >    Vmax Read signal - Vmin Read signal
.
(Step4) When contaminated media is encountered, the input signal in
step3 is higher than the set reference level. Output of comparator
switches to HIGH (LOW). This signal will toggle the spindle motor to
disable FDD operation. Another signal will be sent to the interface
to warn of a BAD media. Contaminated media is one of the main causes
of NDF (Non-defin...