(19)
(11) EP 0 482 746 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
01.07.1992 Bulletin 1992/27

(43) Date of publication A2:
29.04.1992 Bulletin 1992/18

(21) Application number: 91307969.5

(22) Date of filing: 30.08.1991
(51) International Patent Classification (IPC)5G09G 5/14, G09G 5/06
(84) Designated Contracting States:
DE FR GB IT

(30) Priority: 23.10.1990 US 601835

(71) Applicant: International Business Machines Corporation
Armonk, N.Y. 10504 (US)

(72) Inventors:
  • Robertson, Taggart Huth
    Woodstock, New York 12498 (US)
  • Schanely, Paul Mark
    Kingston, New York 12401 (US)

(74) Representative: Burt, Roger James, Dr. 
IBM United Kingdom Limited Intellectual Property Department Hursley Park
Winchester Hampshire SO21 2JN
Winchester Hampshire SO21 2JN (GB)


(56) References cited: : 
   
       


    (54) Multiple-window lookup table selection


    (57) A system for selecting from multiple palette lookup tables (LUTs) in a multiple-window system without requiring extra planes in video memory for storing palette information. X and Y position signals representing the current position on the screen are compared with the X and Y minima and maxima of each of the defined windows to determine whether the current position is within one or more windows. If the current position is within two or more windows, the window with the highest priority, as stored in a programmable priority register, is selected, and the lookup table is selected that is assigned to that window by a programmable lookup table register. Successive groups of pixels are processed in parallel to increase the speed of operation.







    Search report