1. Field of the Invention
The present invention relates to writing data onto a disk of a hard disk drive.
2. Background Information
Hard disk drives contain a plurality of magnetic heads that are coupled to rotating disks. The heads write and read information by magnetizing and sensing the magnetic fields of the disk surfaces. Each head is attached to a flexure arm to create a subassembly commonly referred to as a head gimbal assembly (“HGA”). The HGA's are suspended from an actuator arm. The actuator arm has a voice coil motor that can move the heads across the surfaces of the disks.
Data is stored on the disk as a series of ones and zeros. Each bit of data is typically written during an electronic timing window. A disk may be segmented into a plurality of individual magnetic areas. Each area is separated from an adjacent magnetic area by a non-magnetic space. Segmented disks can reduce the amount of magnetic interaction between magnetize areas of the disk. The difficulty with segmented disks is timing the writing to align with a magnetic area. For example, a head may write a bit when the write element is between two magnetic areas, causing magnetization of both areas. Such an event will create an additional bit in the bit stream.
It is difficult to detect such error bits because the read channel of the drive is continuously reading a stream of ones and zeros. Standard error correction techniques cannot typically account for added or dropped bits in a stream of data read from a disk. It would be desirable to detect and correct for added or dropped bits in a bitstream read from a disk of a hard drive.