Browse Prior Art Database

Display Scrolling With Disk

IP.com Disclosure Number: IPCOM000087645D
Original Publication Date: 1977-Feb-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Cuzner, DE: AUTHOR [+2]

Abstract

A full-page cathode-ray tube (CRT) image is held on several tracks of a disk D, there being a read head associated with each such track. Fig. 1 shows three tracks with numbered data sectors, each sector containing one raster line of image information. Between each data sector is a gap G such that the interval between sectors is equal to the horizontal flyback of the CRT. Head switching can take place during this gap time, and invariably occurs at an index point I if a full frame has not been displayed.

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Display Scrolling With Disk

A full-page cathode-ray tube (CRT) image is held on several tracks of a disk D, there being a read head associated with each such track. Fig. 1 shows three tracks with numbered data sectors, each sector containing one raster line of image information.

Between each data sector is a gap G such that the interval between sectors is equal to the horizontal flyback of the CRT. Head switching can take place during this gap time, and invariably occurs at an index point I if a full frame has not been displayed.

An operator, by means of an adjustable knob, can select any gap G for a head switching operation and can thereby scroll the image on the CRT. If, for example, there are eight lines to a frame, the choice of gap G3 causes lines 4 to 10 to be displayed, choice of gap G4 causes lines 5 to 11 to be displayed, and so on. Flyback and frame synchronization is chosen to equal the period of one data sector. The system is suitable for interlaced rasters.

Multiple heads are not essential since a convoluted track layout with several tracks crossing at each gap point can be used.

A single read head can be made to track any predetermined path by the sampled servo technique, in which position error information is provided at suitable intervals along the track. By causing a plurality of such paths A, B (Fig.
2) to intersect at the points P, where the servo samples are written, a choice of track is available.

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