US 5,315,568 A · Apparatus and method for accessing sectors of a rotating disk

Abstract

Apparatus and method are provided to increase the capacity of spiral track data storage disks while improving the reliability of access to sectors on the disk. In one embodiment, employed when logical tracks on an optical disk are grouped into concentric bands, previously unusable sectors immediately following a band boundary can be reliably accessed. In accordance with this embodiment, when the target sector is, for example, the first sector of band N and a laser beam from a read head lands on a sector in the previous band N-1, the clock governing the data transfer rate is set to the frequency of the band N-1 and a sector in that band is detected and identified. Based upon the period of sectors in the band N-1, a delay interval is computed which ends when the last sector in the band N-1 rotates past the laser beam. Sector mark detection is disabled during the delay interval and the clock frequency changed to that of band N. Sector mark detection is re-enabled at the end of the delay, the band boundary passes, and the target sector can be detected and accessed. The present invention is also applicable when the target sector is not the first sector in a band as well as when the sector on which the laser beam lands is in the same band as the target sector.

Claims32

Dependent claims

A controller for positioning an optical read head opposite a target sector of a spiral track rotating optical disk having a plurality of bands, each band having a plurality of logical tracks, each track having a plurality of sectors, each sector having a sector mark area, an identification area and a user data area, the controller comprising:

a data transfer clock for regulating the rate at which data is transferred from an optical disk;
means for setting a frequency of said clock to a first frequency when an optical head is positioned opposite a sector P in a first band of the disk, the first clock frequency being a function of the radial distance from an inner disk area to the first band;
means for enabling detection of a sector mark and reading an identification in the sector P and causing said frequency setting means to set the frequency of said clock to a second frequency, the second clock frequency being a function of the radial distance from the inner disk area to a second band of which a target sector is a first sector;
and
means for disabling said sector mark detection means until the optical head is opposite the user data area of a last sector Q in the first band and for re-enabling said sector mark detection means whereby the sector mark of the target sector is detected.

2 more elements

Dependencies are inferred from the claim text.

Apparatus and method for accessing sectors of a rotating disk

Life of this patent

Apparatus and method for accessing sectors of a rotating disk

Life of this patent

Abstract

Claims32