Magnetically Encoded Index Mark
Original Publication Date: 1983-Sep-01
Included in the Prior Art Database: 2005-Feb-07
The beginning of each recording track, of a flexible magnetic recording disk, is identified by a magnetically encoded index mark. The figure shows a floppy disk 10 whose multiple recording tracks lie in a zone 11, 12. A circumferentially-stationary magnetic read/ write head 13 can be radially positioned to transduce any selected track, as the disk rotates about axis 14. Each track includes one index mark (IM) 15 and a plurality of ID/data field zones 17 about the track's 360Œ circumference. Each individual zone 17 includes an identifier (ID) and a data field. To accomplish various functions (such as "ID NOT FOUND IN ONE DISK REVOLUTION") within the disk drive controller, it is necessary to know when a revolution of the disk has occurred. The magnetic transitions of each track's IM field are read by head 13.