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Detection of Minor Disk Asperities Using Successively an all Ones Pattern and an all Zeroes Pattern

IP.com Disclosure Number: IPCOM000051823D
Original Publication Date: 1981-Mar-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 56K

Publishing Venue

IBM

Related People

Mangels, RW: AUTHOR [+2]

Abstract

Asperity detection is particularly useful in connection with phase encoding of data on a disk 10 (Fig. 1) by means of which flux changes 16 and 18 are at the centers or edges of bit cells. A transition 16 written at the center of a bit cell 14 is recognized as a 1 bit, and a transition 18 at the edge of a bit cell 14 is recognized as a 0 bit. Writing of this data is keyed from a predetermined reference point, such as index 20; hence, a 1 bit being written is virtually written in the same area of each bit cell each time. The same is true of a 0 bit.

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Detection of Minor Disk Asperities Using Successively an all Ones Pattern and an all Zeroes Pattern

Asperity detection is particularly useful in connection with phase encoding of data on a disk 10 (Fig. 1) by means of which flux changes 16 and 18 are at the centers or edges of bit cells. A transition 16 written at the center of a bit cell 14 is recognized as a 1 bit, and a transition 18 at the edge of a bit cell 14 is recognized as a 0 bit. Writing of this data is keyed from a predetermined reference point, such as index 20; hence, a 1 bit being written is virtually written in the same area of each bit cell each time. The same is true of a 0 bit.

Previously for detection of a disk asperity 22 (Fig. 2), either an all 1's pattern was written on a disk or else an all 0's pattern was written on the disk, and then this data was read back using magnetic head 24 to locate defect areas which would cause data errors. However, if the asperity was in the all 1's pattern while only the all 0's pattern was read, the asperity would not be located.

This would also be true if the asperity were located in the all 0's pattern, while only the all 1's pattern was read.

The detection here includes the examination first of the surface of disk 10 with an all 1's pattern followed by an examination with an all 0's pattern, or vice versa. This examination is accomplished using amplitude detector 26 electrically connected to head 24. The signal amplitude 28 detected and indicated by detect...