Browse Prior Art Database

Index Mark Detector

IP.com Disclosure Number: IPCOM000077468D
Original Publication Date: 1972-Aug-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Kuckein, PA: AUTHOR

Abstract

An index mark detector is shown which provides an output signal whenever a possible valid index is present. If the index being sensed is an invalid index, the system is so notified and the operation being performed is retried.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 83% of the total text.

Page 1 of 2

Index Mark Detector

An index mark detector is shown which provides an output signal whenever a possible valid index is present. If the index being sensed is an invalid index, the system is so notified and the operation being performed is retried.

The index pattern being sensed is shifted into a shift register 1 by clock pulses. The number of stages within the shift register is determined by the length of the index mark to be sensed. The context of the shift register 1 is interrogated by pattern detector 2, which provides a first output whenever a possible valid index is detected to be within the shift register. a second output which is indicative that the desired index is in fact present in the shift register 2, and a third output indicative that no index is being sensed in the shift register. The first output sets the index latch 4. The second output sets a valid latch 3. The third output is used to reset index latch 4 and valid latch 3. The condition of index latch 4 being set and valid latch 3 being not set is interrogated by invertor 5 and AND circuit 6, which in turn sets error latch 7. Error latch 7 indicates that an error index has occurred and is reset by an error-reset pulse.

The use of this index detector provides that an index will not be missed and ignored where the index information has been damaged by some means. Further, spurious indexes are also detected. This index detector has specific application in those areas in which the system must perform...