Bantz et al. [45] Date of Patent: Jul. 7, 1987
• [51] Int. CI." G09G 1/16
[52] U.S. CI 340/721; 340/747;
340/750; 340/799
[58] Field of Search 340/721, 747, 750, 798,
340/799, 745
[56] References Cited
U.S. PATENT DOCUMENTS
3,925,776 12/1975 Swallow 340/747
3,999,168 12/1976 Findley et al 340/172.5
4,005,390 1/1977 Findley 340/172.5
4,090,260 5/1978 Sinobad 365/237
4,093,996 6/1978 Hogan et al 364/900
4,094,000 6/1978 Brudevold 364/900
4,129,858 2/1978 Hara 340/324
4,146,879 3/1979 Nicholson et al 340/734
4,149,145 4/1979 Hartke et al 340/739
4,199,757 4/1980 Ichimi 340/750
4,200,869 4/1980 Murayama et al 340/723
4,205,310 5/1980 McMann, Jr. et al 340/750
4.217.577 8/1980 Roe et al 340/703
4,232,376 11/1980 Dion et al 340/750
4,237,543 12/1980 Nishio et al 364/900
4,241,341 12/1980 Thorson 340/747
4.246.578 1/1981 Kawasaki et al 340/750
4.250.502 2/1981 Klauck et al 340/728
4,258,361 3/1981 Hydes et al 340/721
4,342,051 7/1982 Suzuki et al 358/283
4,367,533 1/1983 Wiener 364/519
4,404,554 9/1983 Tweedy, Jr. et al 340/747
4.442.503 4/1984 Schutt et al 340/747
4,447,809 5/1984 Kodama et al 340/747
4,454,507 6/1984 Srinavasan 340/747
4,587,559 5/1986 Longacre, Jr. et al 340/750
OTHER PUBLICATIONS
Video Display Processor Simulates Three Dimensions, Guttag et al; Electronics; vol. 53, #25, pp. 123-126, 11/80.
D. A. Canton, "Implementation of Refresh Memory in Microprocesor-Controlled Displays", IBM TDB, vol. 25, No. 2, Jul. 1982, p. 843.
P. A. Beaven et al, "Programmable Symbols Technique for Raster-Scanned Display", IBM TDB, vol. 25, No. 2, Jul. 1982, p. 844.
Primary Examiner— Marshall M. Curtis
Attorney, Agent, or Firm—Carl C. Kling
[57] ABSTRACT
Pixel representations for each of a plurality of superimposed (or splitscreen) display portions are accumulated in a band buffer prior to being transferred to the display. The actual pixel representations are made available to the band buffer from an image memory, with addresses provided by a display list memory. This system minimizes the need for buffering and high speed storage to service the video, by addressing first the display list memory, then in turn using the content of the display list memory to address the image storage, and then in turn using the content of the image storage as the actual pixel representations for accumulation in the band buffer. Two band buffers operate alternatively. The current band buffer is feeding a band of pixel representations to the video shift register while the next band buffer is accumulating the pixel representations of the subsequent video display band. The band buffer accumulates actual pixel representations equivalent to the related band of the display. The pixel representations sent to the band buffer from image memory are gated by controls which ensure that the proper pixel prevails in the case of a composite display made up of a primary display with a secondary display which might have higher priority, as, for example, a text announcement superimposed over a normal entertainment program image.
4 Claims, 14 Drawing Figures
