Browse Prior Art Database

Missing Bit Detector

IP.com Disclosure Number: IPCOM000105218D
Original Publication Date: 1993-Jun-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 1 page(s) / 34K

Publishing Venue

IBM

Related People

Laczko, L: AUTHOR [+2]

Abstract

A missing bit (MB) detector is disclosed which is suitable for Head Disk Assembly Surface Analysis testing (HDA/SA). The purpose of SA testing is to identify data bits whose amplitude is lower than a predetermined level. These low amplitude signals can cause data errors, dubbed "missing bits."

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This is the abbreviated version, containing approximately 100% of the total text.

Missing Bit Detector

      A missing bit (MB) detector is disclosed which is suitable for
Head Disk Assembly Surface Analysis testing (HDA/SA).  The purpose of
SA testing is to identify data bits whose amplitude is lower than a
predetermined level.  These low amplitude signals can cause data
errors, dubbed "missing bits."

      The MB detector comprises a pair of clip-level comparators
coupled to at least one single shot (S.S.).  In one embodiment, a
first comparator is adjusted to fire whenever the input data signal
crosses zero.  The output of this comparator is coupled to a S.S.
and to the reset input of a set-reset (SR) latch.  The latch enables
the S.S whenever it is reset.

      A second comparator is adjusted to fire when the input data
signal exceeds a predetermined clip-level voltage.  The output of
this comparator is coupled to the set input of the SR latch.

      In the event of a missing bit, the zero cross comparator fires,
enabling the S.S.  The second clip-level comparator does not fire,
and the S.S.  fails to become disabled.  Thus, when the zero-cross
comparator fires again, the S.S.  generates a signal indicating a
missing bit error.  The S.S.  timing is not critical.

      In contrast to the prior art, this MB detector requires no
alignment or calibration.  Moreover, the S.S.  is not carrier
frequency dependent.  Finally, the circuit is simple and easy to
integrate.

Disclosed Anonymously.